CMP Journal 2025-02-26
Statistics
Nature: 33
Nature Materials: 2
Nature Nanotechnology: 1
Physical Review Letters: 20
Physical Review X: 1
arXiv: 78
Nature
Automated loss of pulse detection on a consumer smartwatch
Original Paper | Arrhythmias | 2025-02-25 19:00 EST
Kamal Shah, Anran Wang, Yiwen Chen, Jitender Munjal, Sumeet Chhabra, Anthony Stange, Enxun Wei, Tuan Phan, Tracy Giest, Beszel Hawkins, Dinesh Puppala, Elsina Silver, Lawrence Cai, Shruti Rajagopalan, Edward Shi, Yun-Ling Lee, Matt Wimmer, Pramod Rudrapatna, Thomas Rea, Shelten Yuen, Anupam Pathak, Shwetak Patel, Mark Malhotra, Marc Stogaitis, Jeanie Phan, Bakul Patel, Adam Vasquez, Christina Fox, Alistair Connell, Jim Taylor, Jacqueline Shreibati, David Miller, Daniel McDuff, Pushmeet Kohli, Tajinder Gadh, Jake Sunshine
Out-of-hospital cardiac arrest is a time-sensitive emergency that requires prompt identification and intervention: sudden, unwitnessed cardiac arrest is nearly unsurvivable1-3. A cardinal sign of cardiac arrest is sudden loss of pulse4. Automated biosensor detection of unwitnessed cardiac arrest, and dispatch of medical assistance, may improve survivability given the significant prognostic role of time3,5, but only if the false positive burden on public emergency medical systems is minimized5-7. Here we show that a multimodal, machine learning-based algorithm on a smartwatch can reach performance thresholds making it deployable at societal scale. First, using photoplethysmography (PPG), we show that wearable PPG measurements of peripheral pulselessness (induced via an arterial occlusion model) manifest similarly to pulselessness caused by a common cardiac arrest arrhythmia, ventricular fibrillation (VF). Based on the similarity of the PPG signal (from VF or arterial occlusion), we developed and validated a loss of pulse detection algorithm using data from peripheral pulselessness and free-living conditions. Once developed, we evaluated the end-to-end algorithm prospectively: there was 1 unintentional emergency call per 21.67 user-years across two prospective studies; the sensitivity was 67.23% (95% confidence interval, 64.32%-70.05%) in a prospective arterial occlusion cardiac arrest simulation model. These results suggest a new opportunity, deployable at scale, for wearable-based detection of sudden loss of pulse while minimizing societal costs of excess false detections7.
Arrhythmias, Biomedical engineering, Clinical trials, Computer science, Translational research
A manufacturable platform for photonic quantum computing
Original Paper | Other photonics | 2025-02-25 19:00 EST
Koen Alexander, Avishai Benyamini, Dylan Black, Damien Bonneau, Stanley Burgos, Ben Burridge, Hugo Cable, Geoff Campbell, Gabriel Catalano, Alejandro Ceballos, Chia-Ming Chang, Sourav Sen Choudhury, CJ Chung, Fariba Danesh, Tom Dauer, Michael Davis, Eric Dudley, Ping Er-Xuan, Josep Fargas, Alessandro Farsi, Colleen Fenrich, Jonathan Frazer, Masaya Fukami, Yogeeswaran Ganesan, Gary Gibson, Mercedes Gimeno-Segovia, Sebastian Goeldi, Patrick Goley, Ryan Haislmaier, Sami Halimi, Paul Hansen, Sam Hardy, Jason Horng, Matthew House, Hong Hu, Mehdi Jadidi, Vijay Jain, Henrik Johansson, Thomas Jones, Vimal Kamineni, Nicholas Kelez, Ravi Koustuban, George Kovall, Peter Krogen, Nikhil Kumar, Yong Liang, Nicholas LiCausi, Dan Llewellyn, Kimberly Lokovic, Michael Lovelady, Vitor Riseti Manfrinato, Ann Melnichuk, Gabriel Mendoza, Brad Moores, Shaunak Mukherjee, Joseph Munns, Francois-Xavier Musalem, Faraz Najafi, Jeremy L. O'Brien, J. Elliott Ortmann, Sunil Pai, Bryan Park, Hsuan-Tung Peng, Nicholas Penthorn, Brennan Peterson, Gabriel Peterson, Matt Poush, Geoff J. Pryde, Tarun Ramprasad, Gareth Ray, Angelita Viejo Rodriguez, Brian Roxworthy, Terry Rudolph, Dylan J. Saunders, Pete Shadbolt, Deesha Shah, Andrea Bahgat Shehata, Hyungki Shin, Jeffrey Sinsky, Jake Smith, Ben Sohn, Young-Ik Sohn, Gyeongho Son, Mario C. M. M. Souza, Chris Sparrow, Matteo Staffaroni, Camille Stavrakas, Vijay Sukumaran, Davide Tamborini, Mark G. Thompson, Khanh Tran, Mark Triplett, Maryann Tung, Andrzej Veitia, Alexey Vert, Mihai D. Vidrighin, Ilya Vorobeichik, Peter Weigel, Mathhew Wingert, Jamie Wooding, Xinran Zhou
Whilst holding great promise for low noise, ease of operation and networking [1], useful photonic quantum computing has been precluded by the need for beyond-state-of-the-art components, manufactured by the millions [2-6]. Here we introduce a manufacturable platform [7] for quantum computing with photons. We benchmark a set of monolithically-integrated silicon photonics-based modules to generate, manipulate, network, and detect heralded photonic qubits, demonstrating dual-rail photonic qubits with 99.98% ± 0.01% state preparation and measurement fidelity, Hong-Ou-Mandel quantum interference between independent photon sources with 99.50% ± 0.25% visibility, two-qubit fusion with 99.22% ± 0.12% fidelity, and a chip-to-chip qubit interconnect with 99.72% ± 0.04% fidelity, conditional on photon detection and not accounting for loss. We preview a selection of next-generation technologies--low-loss silicon nitride waveguides and components to address loss, as well as fabrication-tolerant photon sources, high-efficiency photon-number-resolving detectors, low-loss chip-to-fiber coupling, and barium titanate electro-optic phase shifters for high-performance fast switching.
Other photonics, Photonic devices, Qubits
Spectroscopy of the fractal Hofstadter energy spectrum
Original Paper | Electronic properties and materials | 2025-02-25 19:00 EST
Kevin P. Nuckolls, Michael G. Scheer, Dillon Wong, Myungchul Oh, Ryan L. Lee, Jonah Herzog-Arbeitman, Kenji Watanabe, Takashi Taniguchi, Biao Lian, Ali Yazdani
Hofstadter's butterfly, the predicted energy spectrum for non-interacting electrons confined to a two-dimensional lattice in a magnetic field, is one of the most remarkable fractal structures in nature1. At rational ratios of magnetic flux quanta per lattice unit cell, this spectrum shows self-similar distributions of energy levels that reflect its recursive construction. For most materials, Hofstadter's butterfly is predicted under experimental conditions that are unachievable using laboratory-scale magnetic fields1,2,3. More recently, electrical transport studies have provided evidence for Hofstadter's butterfly in materials engineered to have artificially large lattice constants4,5,6, such as those with moiré superlattices7,8,9,10. Yet, so far, direct spectroscopy of the fractal energy spectrum predicted by Hofstadter nearly 50 years ago has remained out of reach. Here we use high-resolution scanning tunnelling microscopy/spectroscopy (STM/STS) to investigate the flat electronic bands in twisted bilayer graphene (TBG) near the predicted second magic angle11,12, an ideal setting for spectroscopic studies of Hofstadter's spectrum. Our study shows the fractionalization of flat moiré bands into discrete Hofstadter subbands and discerns experimental signatures of self-similarity of this spectrum. Moreover, our measurements uncover a spectrum that evolves dynamically with electron density, showing phenomena beyond that of Hofstadter's original model owing to the combined effects of strong correlations, Coulomb interactions and the quantum degeneracy of electrons in TBG.
Electronic properties and materials, Quantum Hall
Mass-spectrometry-based proteomics: from single cells to clinical applications
Review Paper | Bioinformatics | 2025-02-25 19:00 EST
Tiannan Guo, Judith A. Steen, Matthias Mann
Mass-spectrometry (MS)-based proteomics has evolved into a powerful tool for comprehensively analysing biological systems. Recent technological advances have markedly increased sensitivity, enabling single-cell proteomics and spatial profiling of tissues. Simultaneously, improvements in throughput and robustness are facilitating clinical applications. In this Review, we present the latest developments in proteomics technology, including novel sample-preparation methods, advanced instrumentation and innovative data-acquisition strategies. We explore how these advances drive progress in key areas such as protein-protein interactions, post-translational modifications and structural proteomics. Integrating artificial intelligence into the proteomics workflow accelerates data analysis and biological interpretation. We discuss the application of proteomics to single-cell analysis and spatial profiling, which can provide unprecedented insights into cellular heterogeneity and tissue architecture. Finally, we examine the transition of proteomics from basic research to clinical practice, including biomarker discovery in body fluids and the promise and challenges of implementing proteomics-based diagnostics. This Review provides a broad and high-level overview of the current state of proteomics and its potential to revolutionize our understanding of biology and transform medical practice.
Bioinformatics, Biomarkers, Chemical modification, Mass spectrometry, Proteomics
A lightweight shape-memory alloy with superior temperature-fluctuation resistance
Original Paper | Mechanical properties | 2025-02-25 19:00 EST
Yuxin Song, Sheng Xu, Shunsuke Sato, Inho Lee, Xiao Xu, Toshihiro Omori, Makoto Nagasako, Takuro Kawasaki, Ryoji Kiyanagi, Stefanus Harjo, Wu Gong, Tomáš Grabec, Pavla Stoklasová, Ryosuke Kainuma
In advanced applications such as aerospace and space exploration, materials must balance lightness, functionality and extreme thermal fluctuation resistance1,2. Shape-memory alloys show promise with strength, toughness and substantial strain recovery due to superelasticity, but maintaining low mass and effective operation at cryogenic temperatures is challenging3,4,5,6. We hereby introduce a new shape-memory alloy that adheres to these stringent criteria. Predominantly composed of Ti and Al with a chemical composition of Ti75.25Al20Cr4.75, this alloy is characterized by a low density (4.36 × 103 kg m-3) and a high specific strength (185 × 103 Pa m3 per kg) at room temperature, while showing excellent superelasticity. The superelasticity, owing to a reversible stress-induced phase transformation from an ordered body-centred cubic parent phase to an ordered orthorhombic martensite, allows for a recoverable strain exceeding 7%. This functionality persists across a broad range of temperatures, from deep cryogenic 4.2 K to above room temperature, arising from an unconventional temperature dependence of transformation stresses. Below a certain threshold during cooling, the critical transformation stress inversely correlates with temperature. We interpret this behaviour from the perspective of a temperature-dependent anomalous lattice instability of the parent phase. This alloy holds potential in everyday appliances requiring flexible strain accommodation, as well as components designed for extreme environmental conditions such as deep space and liquefied gases.
Mechanical properties, Metals and alloys
Programs, origins and immunomodulatory functions of myeloid cells in glioma
Original Paper | Cancer microenvironment | 2025-02-25 19:00 EST
Tyler E. Miller, Chadi A. El Farran, Charles P. Couturier, Zeyu Chen, Joshua P. D'Antonio, Julia Verga, Martin A. Villanueva, L. Nicolas Gonzalez Castro, Yuzhou Evelyn Tong, Tariq Al Saadi, Andrew N. Chiocca, Yuanyuan Zhang, David S. Fischer, Dieter Henrik Heiland, Jennifer L. Guerriero, Kevin Petrecca, Mario L. Suva, Alex K. Shalek, Bradley E. Bernstein
Gliomas are incurable malignancies notable for having an immunosuppressive microenvironment with abundant myeloid cells, the immunomodulatory phenotypes of which remain poorly defined1. Here we systematically investigate these phenotypes by integrating single-cell RNA sequencing, chromatin accessibility, spatial transcriptomics and glioma organoid explant systems. We discovered four immunomodulatory expression programs: microglial inflammatory and scavenger immunosuppressive programs, which are both unique to primary brain tumours, and systemic inflammatory and complement immunosuppressive programs, which are also expressed by non-brain tumours. The programs are not contingent on myeloid cell type, developmental origin or tumour mutational state, but instead are driven by microenvironmental cues, including tumour hypoxia, interleukin-1β, TGFβ and standard-of-care dexamethasone treatment. Their relative expression can predict immunotherapy response and overall survival. By associating the respective programs with mediating genomic elements, transcription factors and signalling pathways, we uncover strategies for manipulating myeloid-cell phenotypes. Our study provides a framework to understand immunomodulation by myeloid cells in glioma and a foundation for the development of more-effective immunotherapies.
Cancer microenvironment, Classification and taxonomy, CNS cancer, Gene regulatory networks, Tumour immunology
Macrophages recycle phagocytosed bacteria to fuel immunometabolic responses
Original Paper | Metabolomics | 2025-02-25 19:00 EST
Juliette Lesbats, Aurélia Brillac, Julie A. Reisz, Parnika Mukherjee, Charlène Lhuissier, Mónica Fernández-Monreal, Jean-William Dupuy, Angèle Sequeira, Gaia Tioli, Celia De La Calle Arregui, Benoît Pinson, Daniel Wendisch, Benoît Rousseau, Alejo Efeyan, Leif Erik Sander, Angelo D'Alessandro, Johan Garaude
Macrophages specialize in phagocytosis, a cellular process that eliminates extracellular matter, including microorganisms, through internalization and degradation1,2. Despite the critical role of phagocytosis during bacterial infection, the fate of phagocytosed microbial cargo and its impact on the host cell are poorly understood. In this study, we show that ingested bacteria constitute an alternative nutrient source that skews immunometabolic host responses. By tracing stable isotope-labelled bacteria, we found that phagolysosomal degradation of bacteria provides carbon atoms and amino acids that are recycled into various metabolic pathways, including glutathione and itaconate biosynthesis, and satisfies the bioenergetic needs of macrophages. Metabolic recycling of microbially derived nutrients is regulated by the nutrient-sensing mechanistic target of rapamycin complex C1 and is intricately tied to microbial viability. Dead bacteria, as opposed to live bacteria, are enriched in cyclic adenosine monophosphate, sustain the cellular adenosine monophosphate pool and subsequently activate adenosine monophosphate protein kinase to inhibit the mechanistic target of rapamycin complex C1. Consequently, killed bacteria strongly fuel metabolic recycling and support macrophage survival but elicit decreased reactive oxygen species production and reduced interleukin-1β secretion compared to viable bacteria. These results provide a new insight into the fate of engulfed microorganisms and highlight a microbial viability-associated metabolite that triggers host metabolic and immune responses. Our findings hold promise for shaping immunometabolic intervention for various immune-related pathologies.
Metabolomics, Nutrient signalling, Phagocytes
Evolutionary lability of a key innovation spurs rapid diversification
Original Paper | Adaptive radiation | 2025-02-25 19:00 EST
Nick Peoples, Michael D. Burns, Michalis Mihalitsis, Peter C. Wainwright
Rates of lineage diversification vary considerably across the tree of life, often as a result of evolutionary innovations1,2,3,4,5. Although the ability to produce new traits can vary between clades and may drive ecological transitions6,7,8,9, the impact of differences in the pace at which innovations evolve at macroevolutionary scales has been overlooked. Complex teeth are one innovation that contributed to the evolutionary success of major vertebrate lineages10,11,12. Here we show that evolutionary lability of tooth complexity, but not complexity itself, spurs rapid diversification across ray-finned fishes. Speciation rates are five times higher when transitions between simple and complex teeth occur rapidly. We find that African cichlids are unique among all fishes; they are dominated by lineages that transition between simple and complex teeth at unparalleled rates. This innovation interacted with the ecological versatility of complex teeth to spur rapid adaptive radiations in lakes Malawi, Victoria and Barombi Mbo. The marked effect on diversification stems from the tight association of tooth complexity with microhabitat and diet. Our results show that phylogenetic variation in how innovations evolve can have a stronger effect on patterns of diversification than the innovation itself. Investigating the impact of innovations from this new perspective will probably implicate more traits in causing heterogeneous diversification rates across the tree of life.
Adaptive radiation, Evolutionary theory, Phylogenetics
Integrated analysis of the complete sequence of a macaque genome
Original Paper | Comparative genomics | 2025-02-25 19:00 EST
Shilong Zhang, Ning Xu, Lianting Fu, Xiangyu Yang, Kaiyue Ma, Yamei Li, Zikun Yang, Zhengtong Li, Yu Feng, Xinrui Jiang, Junmin Han, Ruixing Hu, Lu Zhang, Da Lian, Luciana de Gennaro, Annalisa Paparella, Fedor Ryabov, Dan Meng, Yaoxi He, Dongya Wu, Chentao Yang, Yuxiang Mao, Xinyan Bian, Yong Lu, Francesca Antonacci, Mario Ventura, Valery A. Shepelev, Karen H. Miga, Ivan A. Alexandrov, Glennis A. Logsdon, Adam M. Phillippy, Bing Su, Guojie Zhang, Evan E. Eichler, Qing Lu, Yongyong Shi, Qiang Sun, Yafei Mao
The crab-eating macaques (Macaca fascicularis) and rhesus macaques (Macaca mulatta) are pivotal in biomedical and evolutionary research1,2,3. However, their genomic complexity and interspecies genetic differences remain unclear4. Here, we present a complete genome assembly of a crab-eating macaque, revealing 46% fewer segmental duplications and 3.83 times longer centromeres than those of humans5,6. We also characterize 93 large-scale genomic differences between macaques and humans at a single-base-pair resolution, highlighting their impact on gene regulation in primate evolution. Using ten long-read macaque genomes, hundreds of short-read macaque genomes and full-length transcriptome data, we identified roughly 2 Mbp of fixed-genetic variants, roughly 240 Mbp of complex loci, 16.76 Mbp genetic differentiation regions and 110 alternative splice events, potentially associated with various phenotypic differences between the two macaque species. In summary, the integrated genetic analysis enhances understanding of lineage-specific phenotypes, adaptation and primate evolution, thereby improving their biomedical applications in human disease research.
Comparative genomics, DNA sequencing, Evolutionary genetics, Genome informatics
Brain-wide presynaptic networks of functionally distinct cortical neurons
Original Paper | Neural circuits | 2025-02-25 19:00 EST
Ana R. Inácio, Ka Chun Lam, Yuan Zhao, Francisco Pereira, Charles R. Gerfen, Soohyun Lee
Revealing the connectivity of functionally identified individual neurons is necessary to understand how activity patterns emerge and support behaviour. Yet the brain-wide presynaptic wiring rules that lay the foundation for the functional selectivity of individual neurons remain largely unexplored. Cortical neurons, even in primary sensory cortex, are heterogeneous in their selectivity, not only to sensory stimuli but also to multiple aspects of behaviour. Here, to investigate presynaptic connectivity rules underlying the selectivity of pyramidal neurons to behavioural state1,2,3,4,5,6,7,8,9,10 in primary somatosensory cortex (S1), we used two-photon calcium imaging, neuropharmacology, single-cell-based monosynaptic input tracing and optogenetics. We show that behavioural state-dependent activity patterns are stable over time. These are minimally affected by direct neuromodulatory inputs and are driven primarily by glutamatergic inputs. Analysis of brain-wide presynaptic networks of individual neurons with distinct behavioural state-dependent activity profiles revealed that although behavioural state-related and behavioural state-unrelated neurons shared a similar pattern of local inputs within S1, their long-range glutamatergic inputs differed. Individual cortical neurons, irrespective of their functional properties, received converging inputs from the main S1-projecting areas. Yet neurons that tracked behavioural state received a smaller proportion of motor cortical inputs and a larger proportion of thalamic inputs. Optogenetic suppression of thalamic inputs reduced behavioural state-dependent activity in S1, but this activity was not externally driven. Our results reveal distinct long-range glutamatergic inputs as a substrate for preconfigured network dynamics associated with behavioural state.
Neural circuits, Sensorimotor processing
A hypothalamic circuit underlying the dynamic control of social homeostasis
Original Paper | Neural circuits | 2025-02-25 19:00 EST
Ding Liu, Mostafizur Rahman, Autumn Johnson, Ryunosuke Amo, Iku Tsutsui-Kimura, Zuri A. Sullivan, Nicolai Pena, Mustafa Talay, Brandon L. Logeman, Samantha Finkbeiner, Lechen Qian, Seungwon Choi, Athena Capo-Battaglia, Ishmail Abdus-Saboor, David D. Ginty, Naoshige Uchida, Mitsuko Watabe-Uchida, Catherine Dulac
Social grouping increases survival in many species, including humans1,2. By contrast, social isolation generates an aversive state (‘loneliness') that motivates social seeking and heightens social interaction upon reunion3,4,5. The observed rebound in social interaction triggered by isolation suggests a homeostatic process underlying the control of social need, similar to physiological drives such as hunger, thirst or sleep3,6. In this study, we assessed social responses in several mouse strains, among which FVB/NJ mice emerged as highly, and C57BL/6J mice as moderately, sensitive to social isolation. Using both strains, we uncovered two previously uncharacterized neuronal populations in the hypothalamic preoptic nucleus that are activated during either social isolation or social rebound and orchestrate the behaviour display of social need and social satiety, respectively. We identified direct connectivity between these two populations and with brain areas associated with social behaviour, emotional state, reward and physiological needs and showed that mice require touch to assess the presence of others and fulfil their social need. These data show a brain-wide neural system underlying social homeostasis and provide significant mechanistic insights into the nature and function of circuits controlling instinctive social need and for the understanding of healthy and diseased brain states associated with social context.
Neural circuits, Social behaviour
Systems-level design principles of metabolic rewiring in an animal
Original Paper | Biochemical networks | 2025-02-25 19:00 EST
Xuhang Li, Hefei Zhang, Thomas Hodder, Wen Wang, Chad L. Myers, L. Safak Yilmaz, Albertha J. M. Walhout
The regulation of metabolism is vital to any organism and can be achieved by transcriptionally activating or repressing metabolic genes1,2,3. Although many examples of transcriptional metabolic rewiring have been reported4, a systems-level study of how metabolism is rewired in response to metabolic perturbations is lacking in any animal. Here we apply Worm Perturb-Seq (WPS)--a high-throughput method combining whole-animal RNA-interference and RNA-sequencing5--to around 900 metabolic genes in the nematode Caenorhabditis elegans. We derive a metabolic gene regulatory network (mGRN) in which 385 perturbations are connected to 9,414 genes by more than 110,000 interactions. The mGRN has a highly modular structure in which 22 perturbation clusters connect to 44 gene expression programs. The mGRN reveals different modes of transcriptional rewiring from simple reaction and pathway compensation to rerouting and more complex network coordination. Using metabolic network modelling, we identify a design principle of transcriptional rewiring that we name the compensation-repression (CR) model. The CR model explains most transcriptional responses in metabolic genes and reveals a high level of compensation and repression in five core metabolic functions related to energy and biomass. We provide preliminary evidence that the CR model may also explain transcriptional metabolic rewiring in human cells.
Biochemical networks, Gene regulation, Metabolism
Glycocalyx dysregulation impairs blood-brain barrier in ageing and disease
Original Paper | Blood-brain barrier | 2025-02-25 19:00 EST
Sophia M. Shi, Ryan J. Suh, D. Judy Shon, Francisco J. Garcia, Josephine K. Buff, Micaiah Atkins, Lulin Li, Nannan Lu, Bryan Sun, Jian Luo, Ning-Sum To, Tom H. Cheung, M. Windy McNerney, Myriam Heiman, Carolyn R. Bertozzi, Tony Wyss-Coray
The blood-brain barrier (BBB) is highly specialized to protect the brain from harmful circulating factors in the blood and maintain brain homeostasis1,2. The brain endothelial glycocalyx layer, a carbohydrate-rich meshwork composed primarily of proteoglycans, glycoproteins and glycolipids that coats the BBB lumen, is a key structural component of the BBB3,4. This layer forms the first interface between the blood and brain vasculature, yet little is known about its composition and roles in supporting BBB function in homeostatic and diseased states. Here we find that the brain endothelial glycocalyx is highly dysregulated during ageing and neurodegenerative disease. We identify significant perturbation in an underexplored class of densely O-glycosylated proteins known as mucin-domain glycoproteins. We demonstrate that ageing- and disease-associated aberrations in brain endothelial mucin-domain glycoproteins lead to dysregulated BBB function and, in severe cases, brain haemorrhaging in mice. Finally, we demonstrate that we can improve BBB function and reduce neuroinflammation and cognitive deficits in aged mice by restoring core 1 mucin-type O-glycans to the brain endothelium using adeno-associated viruses. Cumulatively, our findings provide a detailed compositional and structural mapping of the ageing brain endothelial glycocalyx layer and reveal important consequences of ageing- and disease-associated glycocalyx dysregulation on BBB integrity and brain health.
Blood-brain barrier, Glycobiology, Neurodegenerative diseases
The conserved HIV-1 spacer peptide 2 triggers matrix lattice maturation
Original Paper | Cryoelectron microscopy | 2025-02-25 19:00 EST
James C. V. Stacey, Dominik Hrebík, Elizabeth Nand, Snehith Dyavari Shetty, Kun Qu, Marius Boicu, Maria Anders-Össwein, Pradeep D. Uchil, Robert A. Dick, Walther Mothes, Hans-Georg Kräusslich, Barbara Müller, John A. G. Briggs
The virus particles of human immunodeficiency virus type 1 (HIV-1) are released in an immature, non-infectious form. Proteolytic cleavage of the main structural polyprotein Gag into functional domains induces rearrangement into mature, infectious virions. In immature virus particles, the Gag membrane-binding domain, MA, forms a hexameric protein lattice that undergoes structural transition, following cleavage, into a distinct, mature MA lattice1. The mechanism of MA lattice maturation is unknown. Here we show that released spacer peptide 2 (SP2), a conserved peptide of unknown function situated about 300 residues downstream of MA, binds MA to induce structural maturation. By high-resolution in-virus structure determination of MA, we show that MA does not bind lipid into a side pocket as previously thought1, but instead binds SP2 as an integral part of the protein-protein interfaces that stabilize the mature lattice. Analysis of Gag cleavage site mutants showed that SP2 release is required for MA maturation, and we demonstrate that SP2 is sufficient to induce maturation of purified MA on lipid monolayers in vitro. SP2-triggered MA maturation correlated with faster fusion of virus with target cells. Our results reveal a new, unexpected interaction between two HIV-1 components, provide a high-resolution structure of mature MA, establish the trigger of MA structural maturation and assign function to the SP2 peptide.
Cryoelectron microscopy, Retrovirus, Virus structures
Continued Atlantic overturning circulation even under climate extremes
Original Paper | Climate and Earth system modelling | 2025-02-25 19:00 EST
J. A. Baker, M. J. Bell, L. C. Jackson, G. K. Vallis, A. J. Watson, R. A. Wood
The Atlantic Meridional Overturning Circulation (AMOC), vital for northwards heat transport in the Atlantic Ocean, is projected to weaken owing to global warming1, with significant global climate impacts2. However, the extent of AMOC weakening is uncertain with wide variation across climate models1,3,4 and some statistical indicators suggesting an imminent collapse5. Here we show that the AMOC is resilient to extreme greenhouse gas and North Atlantic freshwater forcings across 34 climate models. Upwelling in the Southern Ocean, driven by persistent Southern Ocean winds, sustains a weakened AMOC in all cases, preventing its complete collapse. As Southern Ocean upwelling must be balanced by downwelling in the Atlantic or Pacific, the AMOC can only collapse if a compensating Pacific Meridional Overturning Circulation (PMOC) develops. Remarkably, a PMOC does emerge in almost all models, but it is too weak to balance all of the Southern Ocean upwelling, suggesting that an AMOC collapse is unlikely this century. Our findings reveal AMOC-stabilizing mechanisms with implications for past and future AMOC changes, and hence for ecosystems and ocean biogeochemistry. They suggest that better understanding and estimates of the Southern Ocean and Indo-Pacific circulations are urgently needed to accurately predict future AMOC change.
Climate and Earth system modelling, Physical oceanography, Projection and prediction
Comparative characterization of human accelerated regions in neurons
Original Paper | Evolutionary genetics | 2025-02-25 19:00 EST
Xiekui Cui, Han Yang, Charles Cai, Cooper Beaman, Xiaoyu Yang, Hongjiang Liu, Xingjie Ren, Zachary Amador, Ian R. Jones, Kathleen C. Keough, Meng Zhang, Tyler Fair, Armen Abnousi, Shreya Mishra, Zhen Ye, Ming Hu, Alex A. Pollen, Katherine S. Pollard, Yin Shen
Human accelerated regions (HARs) are conserved genomic loci that have experienced rapid nucleotide substitutions following the divergence from chimpanzees1,2. HARs are enriched in candidate regulatory regions near neurodevelopmental genes, suggesting their roles in gene regulation3. However, their target genes and functional contributions to human brain development remain largely uncharacterized. Here we elucidate the cis-regulatory functions of HARs in human and chimpanzee induced pluripotent stem (iPS) cell-induced excitatory neurons. Using genomic4 and chromatin looping information, we prioritized 20 HARs and their chimpanzee orthologues for functional characterization via single-cell CRISPR interference, and demonstrated their species-specific gene regulatory functions. Our findings reveal diverse functional outcomes of HAR-mediated cis-regulation in human neurons, including attenuated NPAS3 expression by altering the binding affinities of multiple transcription factors in HAR202 and maintaining iPS cell pluripotency and neuronal differentiation capacities through the upregulation of PUM2 by 2xHAR.319. Finally, we used prime editing to demonstrate differential enhancer activity caused by several HAR26;2xHAR.178 variants. In particular, we link one variant in HAR26;2xHAR.178 to elevated SOCS2 expression and increased neurite outgrowth in human neurons. Thus, our study sheds new light on the endogenous gene regulatory functions of HARs and their potential contribution to human brain evolution.
Evolutionary genetics, Functional genomics
Clonal Candida auris and ESKAPE pathogens on the skin of residents of nursing homes
Original Paper | Epidemiology | 2025-02-25 19:00 EST
Diana M. Proctor, Sarah E. Sansom, Clay Deming, Sean Conlan, Ryan A. Blaustein, Thomas K. Atkins, Jim Mullikin, Jim Thomas, Alice Young, Gerry Bouffard, Betty Barnabas, Shelise Brooks, Joel Han, Chlöe Buchter, Shi-ling Ho, Juyun Crawford, Richelle Legaspi, Quino Maduro, Holly Marfani, Casandra Montemayor, Nancy Riebow, Karen Schandler, Brian Schmidt, Christina Sison, Mal Stantripop, Sean Black, Mila Dekhtyar, Cathy Masiello, Jenny McDowell, Morgan Park, Pam Thomas, Meg Vemulapalli, Thelma Dangana, Christine Fukuda, Lahari Thotapalli, Heidi H. Kong, Michael Y. Lin, Mary K. Hayden, Julia A. Segre
Antimicrobial resistance is a public health threat associated with increased morbidity, mortality and financial burden in nursing homes and other healthcare settings1. Residents of nursing homes are at increased risk of pathogen colonization and infection owing to antimicrobial-resistant bacteria and fungi. Nursing homes act as reservoirs, amplifiers and disseminators of antimicrobial resistance in healthcare networks and across geographical regions2. Here we investigate the genomic epidemiology of the emerging, multidrug-resistant human fungal pathogen Candida auris in a ventilator-capable nursing home. Coupling strain-resolved metagenomics with isolate sequencing, we report skin colonization and clonal spread of C. auris on the skin of nursing home residents and throughout a metropolitan region. We also report that most Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa and Entobacter species (ESKAPE) pathogens and other high-priority pathogens (including Escherichia coli, Providencia stuartii, Proteus mirabilis and Morganella morganii) are shared in a nursing home. Integrating microbiome and clinical microbiology data, we detect carbapenemase genes at multiple skin sites on residents identified as carriers of these genes. We analyse publicly available shotgun metagenomic samples (stool and skin) collected from residents with varying medical conditions living in seven other nursing homes and provide additional evidence of previously unappreciated bacterial strain sharing. Taken together, our data suggest that skin is a reservoir for colonization by C. auris and ESKAPE pathogens and their associated antimicrobial-resistance genes.
Epidemiology, Metagenomics
Glacial isostatic adjustment reveals Mars's interior viscosity structure
Original Paper | Geodynamics | 2025-02-25 19:00 EST
A. Broquet, A.-C. Plesa, V. Klemann, B. C. Root, A. Genova, M. A. Wieczorek, M. Knapmeyer, J. C. Andrews-Hanna, D. Breuer
Investigating glacial isostatic adjustment has been the standard method to decipher Earth's interior viscosity structure1,2, but such an approach has been rarely applied to other planets because of a lack of observational data3,4. The north polar cap of Mars is the only millions-of-years-old surface feature that can induce measurable surface deformation on this planet, thereby holding clues to its present-day internal viscosity structure5,6. Here we investigate the emplacement of this ice cap by combining thermal evolution models7, viscoelastic deformation calculations8 and radar observations6. We show that downward motion of the northern regions is ongoing and can be constrained by analyses of the time-variable gravity field9 and NASA's InSight seismic moment rate10. Only models with present-day high viscosities (2-6 × 1022 Pa s for depths greater than 500 km), strong mantle depletion in radiogenic elements (more than 90%) and thick average crusts (thicker than 40 km) are consistent with the negligible flexure beneath the polar cap seen by radars. The northern lithosphere must deform at less than 0.13 mm per year and have a seismic efficiency less than 0.3 to satisfy gravity and seismic constraints, respectively. Our models show that the north polar cap formed over the last 1.7-12.0 Myr and that glacial isostatic adjustment can be further constrained by future gravity recovery missions to Mars11,12.
Geodynamics
Multiplexed entanglement of multi-emitter quantum network nodes
Original Paper | Quantum information | 2025-02-25 19:00 EST
A. Ruskuc, C.-J. Wu, E. Green, S. L. N. Hermans, W. Pajak, J. Choi, A. Faraon
Quantum networks that distribute entanglement among remote nodes will unlock transformational technologies in quantum computing, communication and sensing1,2,3,4. However, state-of-the-art networks5,6,7,8,9,10,11,12,13,14 use only a single optically addressed qubit per node; this constrains both the quantum communication bandwidth and memory resources, greatly impeding scalability. Solid-state platforms15,16,17,18,19,20,21,22,23,24 provide a valuable resource for multiplexed quantum networking in which multiple spectrally distinguishable qubits can be hosted in nano-scale volumes. Here we harness this resource by implementing a two-node network consisting of several rare-earth ions coupled to nanophotonic cavities25,26,27,28,29,30,31. This is accomplished with a protocol that entangles distinguishable 171Yb ions through frequency-erasing photon detection combined with real-time quantum feedforward. This method is robust to slow optical frequency fluctuations occurring on timescales longer than a single entanglement attempt: a universal challenge amongst solid-state emitters. We demonstrate the enhanced functionality of these multi-emitter nodes in two ways. First, we mitigate the bottlenecks to the entanglement distribution rate through multiplexed entanglement of two remote ion pairs32,33. Second, we prepare multipartite W-states comprising three distinguishable ions as a resource for advanced quantum networking protocols34,35. These results lay the groundwork for scalable quantum networking based on rare-earth ions.
Quantum information, Quantum optics, Qubits, Single photons and quantum effects
A compendium of human gene functions derived from evolutionary modelling
Original Paper | Evolutionary biology | 2025-02-25 19:00 EST
Marc Feuermann, Huaiyu Mi, Pascale Gaudet, Anushya Muruganujan, Suzanna E. Lewis, Dustin Ebert, Tremayne Mushayahama, Suzanne A. Aleksander, James Balhoff, Seth Carbon, J. Michael Cherry, Harold J. Drabkin, Nomi L. Harris, David P. Hill, Raymond Lee, Colin Logie, Sierra Moxon, Christopher J. Mungall, Paul W. Sternberg, Kimberly Van Auken, Jolene Ramsey, Deborah A. Siegele, Rex L. Chisholm, Petra Fey, Michelle Giglio, Suvarna Nadendla, Giulia Antonazzo, Helen Attrill, Nicholas H. Brown, Phani V. Garapati, Steven Marygold, Saadullah H. Ahmed, Praoparn Asanitthong, Diana Luna Buitrago, Meltem N. Erdol, Matthew C. Gage, Siyao Huang, Mohamed Ali Kadhum, Kan Yan Chloe Li, Miao Long, Aleksandra Michalak, Angeline Pesala, Armalya Pritazahra, Shirin C. C. Saverimuttu, Renzhi Su, Qianhan Xu, Ruth C. Lovering, Judith Blake, Karen Christie, Lori Corbani, Mary E. Dolan, Li Ni, Dmitry Sitnikov, Cynthia Smith, Manuel Lera-Ramirez, Kim Rutherford, Valerie Wood, Peter D'Eustachio, Wendy M. Demos, Jeffrey L. De Pons, Melinda R. Dwinell, G. Thomas Hayman, Mary L. Kaldunski, Anne E. Kwitek, Stanley J. F. Laulederkind, Jennifer R. Smith, Marek A. Tutaj, Mahima Vedi, Shur-Jen Wang, Stacia R. Engel, Kalpana Karra, Stuart R. Miyasato, Robert S. Nash, Marek S. Skrzypek, Shuai Weng, Edith D. Wong, Tilmann Achsel, Maria Andres-Alonso, Claudia Bagni, Àlex Bayés, Thomas Biederer, Nils Brose, John Jia En Chua, Marcelo P. Coba, L. Niels Cornelisse, Jaime de Juan-Sanz, Hana L. Goldschmidt, Eckart D. Gundelfinger, Richard L. Huganir, Cordelia Imig, Reinhard Jahn, Hwajin Jung, Pascal S. Kaeser, Eunjoon Kim, Frank Koopmans, Michael R. Kreutz, Noa Lipstein, Harold D. MacGillavry, Peter S. McPherson, Vincent O'Connor, Rainer Pielot, Timothy A. Ryan, Carlo Sala, Morgan Sheng, Karl-Heinz Smalla, A. B. Smit, Ruud F. Toonen, Jan R. T. van Weering, Matthijs Verhage, Chiara Verpelli, Erika Bakker, Tanya Z. Berardini, Leonore Reiser, Andrea Auchincloss, Kristian Axelsen, Ghislaine Argoud-Puy, Marie-Claude Blatter, Emmanuel Boutet, Lionel Breuza, Alan Bridge, Cristina Casals-Casas, Elisabeth Coudert, Anne Estreicher, Maria Livia Famiglietti, Arnaud Gos, Nadine Gruaz-Gumowski, Chantal Hulo, Nevila Hyka-Nouspikel, Florence Jungo, Philippe Le Mercier, Damien Lieberherr, Patrick Masson, Anne Morgat, Ivo Pedruzzi, Lucille Pourcel, Sylvain Poux, Catherine Rivoire, Shyamala Sundaram, Emily Bowler-Barnett, Hema Bye-A-Jee, Paul Denny, Alexandr Ignatchenko, Rizwan Ishtiaq, Antonia Lock, Yvonne Lussi, Michele Magrane, Maria J. Martin, Sandra Orchard, Pedro Raposo, Elena Speretta, Nidhi Tyagi, Kate Warner, Rossana Zaru, Juancarlos Chan, Stavros Diamantakis, Daniela Raciti, Malcolm Fisher, Christina James-Zorn, Virgilio Ponferrada, Aaron Zorn, Sridhar Ramachandran, Leyla Ruzicka, Monte Westerfield, Paul D. Thomas
A comprehensive, computable representation of the functional repertoire of all macromolecules encoded within the human genome is a foundational resource for biology and biomedical research. The Gene Ontology Consortium has been working towards this goal by generating a structured body of information about gene functions, which now includes experimental findings reported in more than 175,000 publications for human genes and genes in experimentally tractable model organisms1,2. Here, we describe the results of a large, international effort to integrate all of these findings to create a representation of human gene functions that is as complete and accurate as possible. Specifically, we apply an expert-curated, explicit evolutionary modelling approach to all human protein-coding genes. This approach integrates available experimental information across families of related genes into models that reconstruct the gain and loss of functional characteristics over evolutionary time. The models and the resulting set of 68,667 integrated gene functions cover approximately 82% of human protein-coding genes. The functional repertoire reveals a marked preponderance of molecular regulatory functions, and the models provide insights into the evolutionary origins of human gene functions. We show that our set of descriptions of functions can improve the widely used genomic technique of Gene Ontology enrichment analysis. The experimental evidence for each functional characteristic is recorded, thereby enabling the scientific community to help review and improve the resource, which we have made publicly available.
Evolutionary biology, Functional genomics, Gene ontology, Molecular evolution, Phylogeny
Achieving kilowatt-scale elastocaloric cooling by a multi-cell architecture
Original Paper | Devices for energy harvesting | 2025-02-25 19:00 EST
Guoan Zhou, Lingyun Zhang, Zexi Li, Peng Hua, Qingping Sun, Shuhuai Yao
Elastocaloric cooling using shape memory alloys (SMAs) has attracted considerable interest as an environmentally friendly, energy-efficient alternative to conventional vapour-compression refrigeration1,2. However, the limited cooling power of existing devices (≤300 W) hampers the commercialization of this technology3,4. Here we constructed a kilowatt-scale elastocaloric cooling device using compressive tubular NiTi in an ‘SMAs in series-fluid in parallel' architecture, referred to as the multi-cell architecture. A large specific cooling power of 12.3 W g-1 was achieved by the large surface-area-to-volume ratio of thin-walled tubular NiTi at high-frequency operation (3.5 Hz), complemented by graphene nanofluid as an efficient heat transfer agent. Furthermore, the multi-cell architecture ensures a sufficient elastocaloric mass for tight assembly while maintaining a low system fluid pressure. Our device achieves a cooling power of 1,284 W on the fluid side at zero temperature lift during the initial 500,000 cycles, demonstrating the potential of this green cooling technology for a decarbonized future5,6.
Devices for energy harvesting, Materials for energy and catalysis
A single-fibre computer enables textile networks and distributed inference
Original Paper | Electrical and electronic engineering | 2025-02-25 19:00 EST
Nikhil Gupta, Henry Cheung, Syamantak Payra, Gabriel Loke, Jenny Li, Yongyi Zhao, Latika Balachander, Ella Son, Vivian Li, Samuel Kravitz, Sehar Lohawala, John Joannopoulos, Yoel Fink
Despite advancements in wearable technologies1,2, barriers remain in achieving distributed computation located persistently on the human body. Here a textile fibre computer that monolithically combines analogue sensing, digital memory, processing and communication in a mass of less than 5 g is presented. Enabled by a foldable interposer, the two-dimensional pad architectures of microdevices were mapped to three-dimensional cylindrical layouts conforming to fibre geometry. Through connection with helical copper microwires, eight microdevices were thermally drawn into a machine-washable elastic fibre capable of more than 60% stretch. This programmable fibre, which incorporates a 32-bit floating-point microcontroller, independently performs edge computing tasks even when braided, woven, knitted or seam-sewn into garments. The universality of the assembly process allows for the integration of additional functions with simple modifications, including a rechargeable fibre power source that operates the computer for nearly 6 h. Finally, we surmount the perennial limitation of rigid interconnects by implementing two wireless communication schemes involving woven optical links and seam-inserted radio-frequency communications. To demonstrate its utility, we show that garments equipped with four fibre computers, one per limb, operating individually trained neural networks achieve, on average, 67% accuracy in classifying physical activity. However, when networked, inference accuracy increases to 95% using simple weighted voting.
Electrical and electronic engineering, Electronic devices
Humans in Africa's wet tropical forests 150 thousand years ago
Original Paper | Archaeology | 2025-02-25 19:00 EST
Eslem Ben Arous, James A. Blinkhorn, Sarah Elliott, Christopher A. Kiahtipes, Charles D. N'zi, Mark D. Bateman, Mathieu Duval, Patrick Roberts, Robert Patalano, Alexander F. Blackwood, Khady Niang, Eugénie Affoua Kouamé, Edith Lebato, Emily Hallett, Jacopo N. Cerasoni, Erin Scott, Jana Ilgner, Maria Jesús Alonso Escarza, Francois Yodé Guédé, Eleanor M. L. Scerri
Humans emerged across Africa shortly before 300 thousand years ago (ka)1,2,3. Although this pan-African evolutionary process implicates diverse environments in the human story, the role of tropical forests remains poorly understood. Here we report a clear association between late Middle Pleistocene material culture and a wet tropical forest in southern Côte d'Ivoire, a region of present-day rainforest. Twinned optically stimulated luminescence and electron spin resonance dating methods constrain the onset of human occupations at Bété I to around 150 ka, linking them with Homo sapiens. Plant wax biomarker, stable isotope, phytolith and pollen analyses of associated sediments all point to a wet forest environment. The results represent the oldest yet known clear association between humans and this habitat type. The secure attribution of stone tool assemblages with the wet forest environment demonstrates that Africa's forests were not a major ecological barrier for H. sapiens as early as around 150 ka.
Archaeology
Genome-coverage single-cell histone modifications for embryo lineage tracing
Original Paper | Developmental biology | 2025-02-25 19:00 EST
Min Liu, Yanzhu Yue, Xubin Chen, Kexin Xian, Chao Dong, Ming Shi, Haiqing Xiong, Kang Tian, Yuzhe Li, Qiangfeng Cliff Zhang, Aibin He
Substantial epigenetic resetting during early embryo development from fertilization to blastocyst formation ensures zygotic genome activation and leads to progressive cellular heterogeneities1,2,3. Mapping single-cell epigenomic profiles of core histone modifications that cover each individual cell is a fundamental goal in developmental biology. Here we develop target chromatin indexing and tagmentation (TACIT), a method that enabled genome-coverage single-cell profiling of seven histone modifications across mouse early embryos. We integrated these single-cell histone modifications with single-cell RNA sequencing data to chart a single-cell resolution epigenetic landscape. Multimodal chromatin-state annotations showed that the onset of zygotic genome activation at the early two-cell stage already primes heterogeneities in totipotency. We used machine learning to identify totipotency gene regulatory networks, including stage-specific transposable elements and putative transcription factors. CRISPR activation of a combination of these identified transcription factors induced totipotency activation in mouse embryonic stem cells. Together with single-cell co-profiles of multiple histone modifications, we developed a model that predicts the earliest cell branching towards the inner cell mass and the trophectoderm in latent multimodal space and identifies regulatory elements and previously unknown lineage-specifying transcription factors. Our work provides insights into single-cell epigenetic reprogramming, multimodal regulation of cellular lineages and cell-fate priming during mouse pre-implantation development.
Developmental biology, Epigenetics, Next-generation sequencing
Orbital hybridization in graphene-based artificial atoms
Original Paper | Electronic properties and devices | 2025-02-25 19:00 EST
Yue Mao, Hui-Ying Ren, Xiao-Feng Zhou, Hao Sheng, Yun-Hao Xiao, Yu-Chen Zhuang, Ya-Ning Ren, Lin He, Qing-Feng Sun
Intra-atomic orbital hybridization and interatomic bond formation are the two fundamental processes when real atoms are condensed to form matter1,2. Artificial atoms mimic real atoms by demonstrating discrete energy levels attributable to quantum confinement3,4,5,6,7,8. As such, they offer a solid-state analogue for simulating intra-atomic orbital hybridization and interatomic bond formation. Signatures of interatomic bond formation have been extensively observed in various artificial atoms9,10,11,12,13,14,15,16,17. However, direct evidence of the intra-atomic orbital hybridization in the artificial atoms remains to be experimentally demonstrated. Here we realize the orbital hybridization in artificial atoms by altering the shape of the artificial atoms. The anisotropy of the confining potential gives rise to the hybridization between quasibound states with different orbital quantum numbers within the artificial atom. These hybridized orbits are directly visualized in real space in our experiment and are well reproduced by both numerical calculations and analytical derivations. Our study opens an avenue for designing artificial matter that cannot be accessed on real atoms through experiments. Moreover, the results obtained inspire the progressive control of quantum states in diverse systems.
Electronic properties and devices, Molecular electronics, Quantum dots, Surfaces, interfaces and thin films
Interplay of geometrical and spin chiralities in 3D twisted magnetic ribbons
Original Paper | Magnetic devices | 2025-02-25 19:00 EST
André M. A. Farinha, See-Hun Yang, Jiho Yoon, Banabir Pal, Stuart S. P. Parkin
Chirality is a ubiquitous and fundamental asymmetry in nature1,2. Recently, the interaction of chiral objects with spin currents has attracted enormous attention from both scientific and technological perspectives3,4,5. Of particular interest is the current-driven motion of chiral topological excitations such as chiral magnetic domain walls in chiral three-dimensional magnetic structures that could allow for high-density memory-storage devices. Here we use state-of-the-art multiphoton lithography6,7 to create three-dimensional chiral magnetic ribbons and perform current-induced motion of chiral domain walls. The ribbons are designed to have a clockwise or anticlockwise chiral twist with a variable magnitude. We find that domain walls can either pass through the ribbon or are impeded, depending on their chirality and configuration and the geometrical chiral twist of the ribbon. The interplay between the magnetic exchange energy and the geometrical twist generates a torsional field that favours chiral Bloch-type walls rather than the Néel-type wall favoured by the intrinsic magnetic properties of the magnetic ribbon itself. Furthermore, the interplay of spin chirality and chiral twist results in a non-reciprocal domain wall motion, namely, a domain wall filter or diode8,9,10. Our findings show how the interplay between geometrical and spin chiralities can lead to new functionalities that could allow for innovative chiral spintronics.
Magnetic devices, Spintronics
Disorder-assisted real-momentum topological photonic crystal
Original Paper | Photonic crystals | 2025-02-25 19:00 EST
Haoye Qin, Zengping Su, Zhe Zhang, Wenjing Lv, Zijin Yang, Weijin Chen, Xinyue Gao, Heng Wei, Yuzhi Shi, Bo Li, Ji Zhou, Romain Fleury, Cheng-Wei Qiu, Qinghua Song
Topological defects and disorder counteract each other1,2,3,4,5. Intuitively, disorder is considered detrimental, requiring efforts to mitigate its effects in conventional topological photonics6,7,8,9. We propose a counter-intuitive approach that exploits a real-momentum topological photonic crystal that harnesses real-space disorder to generate a Pancharatnam-Berry phase10,11, without disrupting the momentum-space singularity originating from bound states in the continuum12. This methodology allows flat optical devices to encode spatial information or even extra topological charge in real space while preserving the topology of bound states in the continuum in momentum space with inherent alignment. Here, as a proof of concept, we demonstrate the simultaneous and independent generation of a real-space broadband vortex or a holographic image alongside resonant momentum-space vortex beams with a narrow bandwidth, which cannot be achieved with conventional methods. Such engineered disorder contributes to vast intrinsic freedoms without adding extra dimensions or compromising the optical flatness13,14. Our findings of real-momentum duality not only lay the foundation for disorder engineering in topological photonics but also open new avenues for optical wavefront shaping, encryption and communications.
Photonic crystals
Latitudinal scaling of aggregation with abundance and coexistence in forests
Original Paper | Biodiversity | 2025-02-25 19:00 EST
Thorsten Wiegand, Xugao Wang, Samuel M. Fischer, Nathan J. B. Kraft, Norman A. Bourg, Warren Y. Brockelman, Guanghong Cao, Min Cao, Wirong Chanthorn, Chengjin Chu, Stuart Davies, Sisira Ediriweera, C. V. Savitri Gunatilleke, I. A. U. Nimal Gunatilleke, Zhanqing Hao, Robert Howe, Mingxi Jiang, Guangze Jin, W. John Kress, Buhang Li, Juyu Lian, Luxiang Lin, Feng Liu, Keping Ma, William McShea, Xiangcheng Mi, Jonathan A. Myers, Anuttara Nathalang, David A. Orwig, Guochun Shen, Sheng-Hsin Su, I-Fang Sun, Xihua Wang, Amy Wolf, Enrong Yan, Wanhui Ye, Yan Zhu, Andreas Huth
The search for simple principles that underlie the spatial structure and dynamics of plant communities is a long-standing challenge in ecology1,2,3,4,5,6. In particular, the relationship between species coexistence and the spatial distribution of plants is challenging to resolve in species-rich communities7,8,<a aria-label="Reference 9" data-test="citation-ref" data-track="click" data-track-action="reference anchor" data-track-label="link" href="https://www.nature.com/articles/s41586-025-08604-z#ref-CR9" id="ref-link-section-d2710816e1251" title="Ellner, S. P., Snyder, R. E., Adler, P. B. & Hooker, G. Toward a "modern coexistence theory" for the discrete and spatial. Ecol. Monogr. 92, e1548 (2022).">9. Here we present a comprehensive analysis of the spatial patterns of 720 tree species in 21 large forest plots and their consequences for species coexistence. We show that species with low abundance tend to be more spatially aggregated than more abundant species. Moreover, there is a latitudinal gradient in the strength of this negative aggregation-abundance relationship that increases from tropical to temperate forests. We suggest, in line with recent work10, that latitudinal gradients in animal seed dispersal11 and mycorrhizal associations12,13,14 may jointly generate this pattern. By integrating the observed spatial patterns into population models8, we derive the conditions under which species can invade from low abundance in terms of spatial patterns, demography, niche overlap and immigration. Evaluation of the spatial-invasion condition for the 720 tree species analysed suggests that temperate and tropical forests both meet the invasion criterion to a similar extent but through contrasting strategies conditioned by their spatial patterns. Our approach opens up new avenues for the integration of observed spatial patterns into ecological theory and underscores the need to understand the interaction among spatial patterns at the neighbourhood scale and multiple ecological processes in greater detail.
Biodiversity, Ecological modelling, Forest ecology, Theoretical ecology
Rare disease gene association discovery in the 100,000 Genomes Project
Original Paper | Genetic association study | 2025-02-25 19:00 EST
Valentina Cipriani, Letizia Vestito, Emma F. Magavern, Julius O. B. Jacobsen, Gavin Arno, Elijah R. Behr, Katherine A. Benson, Marta Bertoli, Detlef Bockenhauer, Michael R. Bowl, Kate Burley, Li F. Chan, Patrick Chinnery, Peter J. Conlon, Marcos A. Costa, Alice E. Davidson, Sally J. Dawson, Elhussein A. E. Elhassan, Sarah E. Flanagan, Marta Futema, Daniel P. Gale, Sonia García-Ruiz, Cecilia Gonzalez Corcia, Helen R. Griffin, Sophie Hambleton, Amy R. Hicks, Henry Houlden, Richard S. Houlston, Sarah A. Howles, Robert Kleta, Iris Lekkerkerker, Siying Lin, Petra Liskova, Hannah H. Mitchison, Heba Morsy, Andrew D. Mumford, William G. Newman, Ruxandra Neatu, Edel A. O'Toole, Albert C. M. Ong, Alistair T. Pagnamenta, Shamima Rahman, Neil Rajan, Peter N. Robinson, Mina Ryten, Omid Sadeghi-Alavijeh, John A. Sayer, Claire L. Shovlin, Jenny C. Taylor, Omri Teltsh, Ian Tomlinson, Arianna Tucci, Clare Turnbull, Albertien M. van Eerde, James S. Ware, Laura M. Watts, Andrew R. Webster, Sarah K. Westbury, Sean L. Zheng, Mark Caulfield, Damian Smedley
Up to 80% of rare disease patients remain undiagnosed after genomic sequencing1, with many probably involving pathogenic variants in yet to be discovered disease-gene associations. To search for such associations, we developed a rare variant gene burden analytical framework for Mendelian diseases, and applied it to protein-coding variants from whole-genome sequencing of 34,851 cases and their family members recruited to the 100,000 Genomes Project2. A total of 141 new associations were identified, including five for which independent disease-gene evidence was recently published. Following in silico triaging and clinical expert review, 69 associations were prioritized, of which 30 could be linked to existing experimental evidence. The five associations with strongest overall genetic and experimental evidence were monogenic diabetes with the known β cell regulator3,4 UNC13A, schizophrenia with GPR17, epilepsy with RBFOX3, Charcot-Marie-Tooth disease with ARPC3 and anterior segment ocular abnormalities with POMK. Further confirmation of these and other associations could lead to numerous diagnoses, highlighting the clinical impact of large-scale statistical approaches to rare disease-gene association discovery.
Genetic association study, Genetic variation, Genetics research, Medical genetics, Statistical methods
A systems-level, semi-quantitative landscape of metabolic flux in C. elegans
Original Paper | Biochemical networks | 2025-02-25 19:00 EST
Hefei Zhang, Xuhang Li, L. Tenzin Tseyang, Gabrielle E. Giese, Hui Wang, Bo Yao, Jingyan Zhang, Rachel L. Neve, Elizabeth A. Shank, Jessica B. Spinelli, L. Safak Yilmaz, Albertha J. M. Walhout
Metabolic flux, or the rate of metabolic reactions, is one of the most fundamental metrics describing the status of metabolism in living organisms. However, measuring fluxes across the entire metabolic network remains nearly impossible, especially in multicellular organisms. Computational methods based on flux balance analysis have been used with genome-scale metabolic network models to predict network-level flux wiring1,2,3,4,5,6. However, such approaches have limited power because of the lack of experimental constraints. Here, we introduce a strategy that infers whole-animal metabolic flux wiring from transcriptional phenotypes in the nematode Caenorhabditis elegans. Using a large-scale Worm Perturb-Seq (WPS) dataset for roughly 900 metabolic genes7, we show that the transcriptional response to metabolic gene perturbations can be integrated with the metabolic network model to infer a highly constrained, semi-quantitative flux distribution. We discover several features of adult C. elegans metabolism, including cyclic flux through the pentose phosphate pathway, lack of de novo purine synthesis flux and the primary use of amino acids and bacterial RNA as a tricarboxylic acid cycle carbon source, all of which we validate by stable isotope tracing. Our strategy for inferring metabolic wiring based on transcriptional phenotypes should be applicable to a variety of systems, including human cells.
Biochemical networks, Metabolism
Hardware-efficient quantum error correction via concatenated bosonic qubits
Original Paper | Quantum information | 2025-02-25 19:00 EST
Harald Putterman, Kyungjoo Noh, Connor T. Hann, Gregory S. MacCabe, Shahriar Aghaeimeibodi, Rishi N. Patel, Menyoung Lee, William M. Jones, Hesam Moradinejad, Roberto Rodriguez, Neha Mahuli, Jefferson Rose, John Clai Owens, Harry Levine, Emma Rosenfeld, Philip Reinhold, Lorenzo Moncelsi, Joshua Ari Alcid, Nasser Alidoust, Patricio Arrangoiz-Arriola, James Barnett, Przemyslaw Bienias, Hugh A. Carson, Cliff Chen, Li Chen, Harutiun Chinkezian, Eric M. Chisholm, Ming-Han Chou, Aashish Clerk, Andrew Clifford, R. Cosmic, Ana Valdes Curiel, Erik Davis, Laura DeLorenzo, J. Mitchell D'Ewart, Art Diky, Nathan D'Souza, Philipp T. Dumitrescu, Shmuel Eisenmann, Essam Elkhouly, Glen Evenbly, Michael T. Fang, Yawen Fang, Matthew J. Fling, Warren Fon, Gabriel Garcia, Alexey V. Gorshkov, Julia A. Grant, Mason J. Gray, Sebastian Grimberg, Arne L. Grimsmo, Arbel Haim, Justin Hand, Yuan He, Mike Hernandez, David Hover, Jimmy S. C. Hung, Matthew Hunt, Joe Iverson, Ignace Jarrige, Jean-Christophe Jaskula, Liang Jiang, Mahmoud Kalaee, Rassul Karabalin, Peter J. Karalekas, Andrew J. Keller, Amirhossein Khalajhedayati, Aleksander Kubica, Hanho Lee, Catherine Leroux, Simon Lieu, Victor Ly, Keven Villegas Madrigal, Guillaume Marcaud, Gavin McCabe, Cody Miles, Ashley Milsted, Joaquin Minguzzi, Anurag Mishra, Biswaroop Mukherjee, Mahdi Naghiloo, Eric Oblepias, Gerson Ortuno, Jason Pagdilao, Nicola Pancotti, Ashley Panduro, JP Paquette, Minje Park, Gregory A. Peairs, David Perello, Eric C. Peterson, Sophia Ponte, John Preskill, Johnson Qiao, Gil Refael, Rachel Resnick, Alex Retzker, Omar A. Reyna, Marc Runyan, Colm A. Ryan, Abdulrahman Sahmoud, Ernesto Sanchez, Rohan Sanil, Krishanu Sankar, Yuki Sato, Thomas Scaffidi, Salome Siavoshi, Prasahnt Sivarajah, Trenton Skogland, Chun-Ju Su, Loren J. Swenson, Stephanie M. Teo, Astrid Tomada, Giacomo Torlai, E. Alex Wollack, Yufeng Ye, Jessica A. Zerrudo, Kailing Zhang, Fernando G. S. L. Brandão, Matthew H. Matheny, Oskar Painter
To solve problems of practical importance1,2, quantum computers probably need to incorporate quantum error correction, in which a logical qubit is redundantly encoded in many noisy physical qubits3,4,5. The large physical-qubit overhead associated with error correction motivates the search for more hardware-efficient approaches6,7,8,9,10,11,12,13,14,15,16,17,18. Here, using a superconducting quantum circuit19, we realize a logical qubit memory formed from the concatenation of encoded bosonic cat qubits with an outer repetition code of distance d = 5 (ref. 10). A stabilizing circuit passively protects cat qubits against bit flips20,21,22,23,24. The repetition code, using ancilla transmons for syndrome measurement, corrects cat qubit phase flips. We study the performance and scaling of the logical qubit memory, finding that the phase-flip correcting repetition code operates below the threshold. The logical bit-flip error is suppressed with increasing cat qubit mean photon number, enabled by our realization of a cat-transmon noise-biased CX gate. The minimum measured logical error per cycle is on average 1.75(2)% for the distance-3 code sections, and 1.65(3)% for the distance-5 code. Despite the increased number of fault locations of the distance-5 code, the high degree of noise bias preserved during error correction enables comparable performance. These results, where the intrinsic error suppression of the bosonic encodings enables us to use a hardware-efficient outer error-correcting code, indicate that concatenated bosonic codes can be a compelling model for reaching fault-tolerant quantum computation.
Quantum information, Qubits, Superconducting devices
A travelling-wave strategy for plant-fungal trade
Original Paper | Biological physics | 2025-02-25 19:00 EST
Loreto Oyarte Galvez, Corentin Bisot, Philippe Bourrianne, Rachael Cargill, Malin Klein, Marije van Son, Jaap van Krugten, Victor Caldas, Thomas Clerc, Kai-Kai Lin, Félix Kahane, Simon van Staalduine, Justin D. Stewart, Victoria Terry, Bianca Turcu, Sander van Otterdijk, Antoine Babu, Marko Kamp, Marco Seynen, Bas Steenbeek, Jan Zomerdijk, Evelina Tutucci, Merlin Sheldrake, Christophe Godin, Vasilis Kokkoris, Howard A. Stone, E. Toby Kiers, Thomas S. Shimizu
For nearly 450 million years, mycorrhizal fungi have constructed networks to collect and trade nutrient resources with plant roots1,2. Owing to their dependence on host-derived carbon, these fungi face conflicting trade-offs in building networks that balance construction costs against geographical coverage and long-distance resource transport to and from roots3. How they navigate these design challenges is unclear4. Here, to monitor the construction of living trade networks, we built a custom-designed robot for high-throughput time-lapse imaging that could track over 500,000 fungal nodes simultaneously. We then measured around 100,000 cytoplasmic flow trajectories inside the networks. We found that mycorrhizal fungi build networks as self-regulating travelling waves--pulses of growing tips pull an expanding wave of nutrient-absorbing mycelium, the density of which is self-regulated by fusion. This design offers a solution to conflicting trade demands because relatively small carbon investments fuel fungal range expansions beyond nutrient-depletion zones, fostering exploration for plant partners and nutrients. Over time, networks maintained highly constant transport efficiencies back to roots, while simultaneously adding loops that shorten paths to potential new trade partners. Fungi further enhance transport flux by both widening hyphal tubes and driving faster flows along ‘trunk routes' of the network5. Our findings provide evidence that symbiotic fungi control network-level structure and flows to meet trade demands, and illuminate the design principles of a symbiotic supply-chain network shaped by millions of years of natural selection.
Biological physics, Coevolution, Fungal biology, Intracellular movement, Microbial ecology
Extensive mutual influences of SMC complexes shape 3D genome folding
Original Paper | Chromatin structure | 2025-02-25 19:00 EST
Han Zhao, Lirong Shu, Shiyi Qin, Fangxuan Lyu, Fuhai Liu, En Lin, Sijian Xia, Baiyue Wang, Manzhu Wang, Fengnian Shan, Yinzhi Lin, Lin Zhang, Yufei Gu, Gerd A. Blobel, Kai Huang, Haoyue Zhang
Mammalian genomes are folded through the distinct actions of structural maintenance of chromosome (SMC) complexes, which include the chromatin loop-extruding cohesin (extrusive cohesin), the sister chromatid cohesive cohesin and the mitotic chromosome-associated condensins1,2,3. Although these complexes function at different stages of the cell cycle, they exist together on chromatin during the G2-to-M phase transition, when the genome structure undergoes substantial reorganization1,2. Yet, how the different SMC complexes affect each other and how their interactions orchestrate the dynamic folding of the three-dimensional genome remain unclear. Here we engineered all possible cohesin and condensin configurations on mitotic chromosomes to delineate the concerted, mutually influential action of SMC complexes. We show that condensin disrupts the binding of extrusive cohesin at CCCTC-binding factor (CTCF) sites, thereby promoting the disassembly of interphase topologically associating domains (TADs) and loops during mitotic progression. Conversely, extrusive cohesin impedes condensin-mediated mitotic chromosome spiralization. Condensin reduces peaks of cohesive cohesin, whereas cohesive cohesin antagonizes condensin-mediated longitudinal shortening of mitotic chromosomes. The presence of both extrusive and cohesive cohesin synergizes these effects and inhibits mitotic chromosome condensation. Extrusive cohesin positions cohesive cohesin at CTCF-binding sites. However, cohesive cohesin by itself cannot be arrested by CTCF molecules and is insufficient to establish TADs or loops. Moreover, it lacks loop-extrusion capacity, which indicates that cohesive cohesin has nonoverlapping functions with extrusive cohesin. Finally, cohesive cohesin restricts chromatin loop expansion mediated by extrusive cohesin. Collectively, our data describe a three-way interaction among major SMC complexes that dynamically modulates chromatin architecture during cell cycle progression.
Chromatin structure, Cohesion, Mitosis
Nature Materials
Rapid self-strengthening in double-network hydrogels triggered by bond scission
Original Paper | Gels and hydrogels | 2025-02-25 19:00 EST
Zhi Jian Wang, Wei Li, Xueyu Li, Tasuku Nakajima, Michael Rubinstein, Jian Ping Gong
The scission of chemical bonds in materials can lead to catastrophic failure, with weak bonds typically undermining the materials' strength. Here we demonstrate how weak bonds can be leveraged to achieve self-strengthening in polymer network materials. These weak sacrificial bonds trigger mechanochemical reactions, forming new networks rapidly enough to reinforce the material during deformation and significantly improve crack resistance. This rapid strengthening exhibits strong rate dependence, dictated by the interplay between bond breaking and the kinetics of force-induced network formation. As the network formation is generally applicable to diverse monomers and crosslinkers with different kinetics, a wide range of mechanical properties can be obtained. These findings may inspire the design of tough polymer materials with on-demand, rate-dependent mechanical behaviours through mechanochemistry, broadening their applications across various fields.
Gels and hydrogels, Mechanical properties
High electrostrain in a lead-free piezoceramic from a chemopiezoelectric effect
Original Paper | Actuators | 2025-02-25 19:00 EST
Ze Xu, Xiaoming Shi, Yi-Xuan Liu, Danyang Wang, Hao-Cheng Thong, Yuqi Jiang, Zijie Sha, Zhao Li, Fang-Zhou Yao, Xian-Xian Cai, Hao-Feng Huang, Zhanpeng Xu, Xinyu Jin, Chen-Bo-Wen Li, Xin Zhang, Xiaowei Ren, Zhihao Dong, Chaofeng Wu, Peter Kabakov, Fangyuan Zhu, Feng Chen, Peng Tan, Hao Tian, Haozhi Sha, Rong Yu, Ben Xu, Wen Gong, Xiaohui Wang, Jing-Feng Li, Stephen J. Skinner, Ming Li, Houbing Huang, Shujun Zhang, Ke Wang
Piezoelectric materials are indispensable in electromechanical actuators, which require a large electrostrain with a fast and precise response. By designing a chemopiezoelectric effect, we developed an approach to achieve a high electrostrain of 1.9% under -3 kV mm-1, at 1 Hz, corresponding to an effective piezoelectric coefficient of >6,300 pm V-1 at room temperature in lead-free potassium sodium niobate piezoceramics. This electrostrain has satisfactory fatigue resistance and thermal stability, and low hysteresis, far outperforming existing lead-based and lead-free perovskite counterparts. From tracer diffusion, atomic optical emission spectrometry experiments, combined with machine-learning molecular dynamics and phase-field simulations, we attribute the high electrostrain to short-range hopping of oxygen vacancies near ceramic surfaces under an alternating electric field, which is supported by strain levels reaching 3.0% under the same applied field when the sample was annealed at a low oxygen partial pressure. These findings provide an additional degree of freedom for designing materials on the basis of defect engineering, which will favour not only the electrostrain of piezoelectrics but also the functional properties of a broader range of oxide-based materials.
Actuators, Ferroelectrics and multiferroics
Nature Nanotechnology
A bioinspired polymeric membrane-enclosed insulin crystal achieves long-term, self-regulated drug release for type 1 diabetes therapy
Original Paper | Biomedical engineering | 2025-02-25 19:00 EST
Jianchang Xu, Yang Zhang, Sheng Zhao, Juan Zhang, Yanfang Wang, Wei Liu, Kangfan Ji, Guangzheng Xu, Ping Wen, Xinwei Wei, Shaoqian Mei, Leihao Lu, Yuejun Yao, Feng Liu, Yufei Ma, Jiahuan You, Jianqing Gao, John B. Buse, Jinqiang Wang, Zhen Gu
The nuclear envelope serves as a highly regulated gateway for macromolecule exchange between the nucleus and cytoplasm in eukaryotes. Here we have developed a cell nucleus-mimicking polymeric membrane-enclosed system for long and self-regulated therapy. A polymeric nano-membrane with nanopores is conformally synthesized in situ on the surface of each insulin crystal, ensuring sustained, adjustable and zero-order drug release kinetics. Glucose- and β-hydroxybutyrate-dually sensitive microdomains are integrated into the nano-membranes. Under a normal state, the microdomains are uncharged and the channel is narrow enough to block insulin outflow. Under hyperglycaemia and ketonaemia, microdomains convert the high glucose and β-hydroxybutyrate concentration signals to the negative electric potential of membranes, widening the nanopores with rapid insulin outflow. In type 1 diabetic mice and minipigs, this system can maintain normoglycaemia for longer than 1 month and 3 weeks, respectively, with validated glucose- and β-hydroxybutyrate-triggered insulin release. Such membrane-enclosed drug crystal/powder formulation provides a broad platform for long-acting controlled release.
Biomedical engineering, Drug delivery
Physical Review Letters
Constraints on Axions from Patchy Screening of the Cosmic Microwave Background
Research article | Cosmic microwave background | 2025-02-26 05:00 EST
Samuel Goldstein, Fiona McCarthy, Cristina Mondino, J. Colin Hill, Junwu Huang, and Matthew C. Johnson
The resonant conversion of cosmic microwave background (CMB) photons into axions within large-scale structure induces an anisotropic spectral distortion in CMB temperature maps. Applying state-of-the-art foreground cleaning techniques to Planck CMB observations, we construct maps of axion-induced ''patchy screening'' of the CMB. We cross-correlate these maps with data from the unWISE galaxy survey and find no evidence of axions. We constrain the axion-photon coupling, \({g}_{a\gamma \gamma }\lesssim 2\times{}{10}^{- 12}\text{ }\text{ }{\mathrm{GeV}}^{- 1}\), at the 95% confidence level for axion masses in the range \({10}^{- 13}\text{ }\text{ }\mathrm{eV}\lesssim {m}_{a}\lesssim {10}^{- 12}\text{ }\text{ }\mathrm{eV}\). These constraints are competitive with the tightest astrophysical axion limits in this mass range and are inferred from robust population-level statistics, which makes them complementary to existing searches that rely on modeling of individual systems.
Phys. Rev. Lett. 134, 081001 (2025)
Cosmic microwave background, Large scale structure of the Universe, Axion-like particles, Galaxy clusters
Instability of Nonsingular Black Holes in Nonlinear Electrodynamics
Research article | General relativity | 2025-02-26 05:00 EST
Antonio De Felice and Shinji Tsujikawa
We show that nonsingular black holes realized in nonlinear electrodynamics are always prone to Laplacian instability around the center because of a negative squared sound speed in the angular direction. This is the case for both electric and magnetic BHs, where the instability of one of the vector-field perturbations leads to enhancing a dynamical gravitational perturbation in the even-parity sector. Thus, the background regular metric is no longer maintained in a steady state. Our results suggest that the construction of stable, nonsingular black holes with regular centers, if they exist, requires theories beyond nonlinear electrodynamics.
Phys. Rev. Lett. 134, 081401 (2025)
General relativity, Astronomical black holes
Black Hole Spectroscopy in Environments: Detectability Prospects
Research article | General relativity | 2025-02-26 05:00 EST
Thomas F. M. Spieksma, Vitor Cardoso, Gregorio Carullo, Matteo Della Rocca, and Francisco Duque
The ringdown phase following a binary black hole coalescence is a powerful tool for measuring properties of the remnant black hole. Future gravitational wave detectors will increase the precision of these measurements and may be sensitive to the environment surrounding the black hole. This work examines how environments affect the ringdown from a binary coalescence. Our analysis shows that for astrophysical parameters and sensitivity of planned detectors, the ringdown signal is indistinguishable from its vacuum counterpart, suggesting that ringdown-only analyses can reliably extract the (redshifted) mass and spin of the remnant black hole. These conclusions include models with spectral instabilities, suggesting that these are not relevant from an observational viewpoint. Deviations from inspiral-only estimates could then enhance the characterisation of environmental effects present during the coalescence.
Phys. Rev. Lett. 134, 081402 (2025)
General relativity, Gravitational waves, Classical black holes
Oscillons from \(Q\)-balls through Renormalization
Research article | Classical solutions in field theory | 2025-02-26 05:00 EST
F. Blaschke, T. Romańczukiewicz, K. Sławińska, and A. Wereszczyński
Using a renormalization-inspired perturbation expansion we show that oscillons in a generic field theory in (\(1+1\)) dimensions arise as dressed Q-balls of a universal (up to the leading nonlinear order) complex field theory. This theory reveals a close similarity to the integrable complex sine-Gordon model, which possesses exact multi-\(Q\)-balls. We show that excited oscillons, with characteristic modulations of their amplitude, are two-oscillons bound states generated from a two \(Q\)-ball solution.
Phys. Rev. Lett. 134, 081601 (2025)
Classical solutions in field theory, Breathers, Solitons
First Measurement of Missing Energy due to Nuclear Effects in Monoenergetic Neutrino Charged-Current Interactions
Research article | Electroweak interactions in nuclear physics | 2025-02-26 05:00 EST
E. Marzec et al. ( Collaboration)
We present the first measurement of the missing energy due to nuclear effects in monoenergetic, muon neutrino charged-current interactions on carbon, originating from \({K}^{+}\rightarrow {\mu }^{+}{\nu }_{\mu }\) decay at rest (\({E}_{ {\nu }_{\mu }}=235.5\text{ }\text{ }\mathrm{MeV}\)), performed with the J-PARC Sterile Neutrino Search at the J-PARC Spallation Neutron Source liquid scintillator based experiment. Toward characterizing the neutrino interaction, ostensibly \({\nu }_{\mu }n\rightarrow {\mu }^{- }p\) or \({\nu }_{\mu }^{12}\mathrm{C}\rightarrow {\mu }^{- }^{12}\mathrm{N}\), we define the missing energy as the energy transferred to the nucleus ($$) minus the kinetic energy of the outgoing proton(s), \({E}_{m}\equiv \omega - \sum {T}_{p}\), and relate this to visible energy in the detector, \({E}_{m}={E}_{ {\nu }_{\mu }}(235.5\text{ }\text{ }\mathrm{MeV})- {m}_{\mu }(105.7\text{ }\text{ }\mathrm{MeV})+[{m}_{n}- {m}_{p}(1.3\text{ }\text{ }\mathrm{MeV})]- {E}_{\mathrm{vis}}\). The missing energy, which is naively expected to be zero in the absence of nuclear effects (e.g., nucleon separation energy, Fermi momenta, and final-state interactions), is uniquely sensitive to many aspects of the interaction, and has previously been inaccessible with neutrinos. The shape-only, differential cross section measurement reported, based on a \((77\pm{}3)%\) pure double-coincidence kaon decay-at-rest signal (621 total events), provides detailed insight into neutrino-nucleus interactions, allowing even the nuclear orbital shell of the struck nucleon to be inferred. The measurement provides an important benchmark for models and event generators at hundreds of MeV neutrino energies, characterized by the difficult-to-model transition region between neutrino-nucleus and neutrino-nucleon scattering, and relevant for applications in nuclear physics, neutrino oscillation measurements, and Type-II supernova studies.
Phys. Rev. Lett. 134, 081801 (2025)
Electroweak interactions in nuclear physics, Neutrino interactions, Nucleus-neutrino interactions, Neutrinos
Search for the \({K}_{L}\rightarrow {\pi }^{0}\nu \overline{\nu }\) Decay at the J-PARC KOTO Experiment
Research article | Cabibbo-Kobayashi-Maskawa matrix | 2025-02-26 05:00 EST
J. K. Ahn et al. (KOTO Collaboration)
We performed a search for the \({K}_{L}\rightarrow {\pi }^{0}\nu \overline{\nu }\) decay using the data taken in 2021 at the J-PARC KOTO experiment. With newly installed counters and new analysis method, the expected background was suppressed to \(0.252\pm{}{0.055}_{\mathrm{stat}}{\text{ }}_{- {0.067}^{\mathrm{syst}}}^{+0.052}\). With a single event sensitivity of \((9.33\pm{}0.0{6}_{\mathrm{stat}}\pm{}0.8{4}_{\mathrm{syst}})\times{}{10}^{- 10}\), no events were observed in the signal region. An upper limit on the branching fraction for the decay was set to be \(2.2\times{}{10}^{- 9}\) at the 90% confidence level (C.L.), which improved the previous upper limit from KOTO by a factor of 1.4. With the same data, a search for \({K}_{L}\rightarrow {\pi }^{0}{X}^{0}\) was also performed, where \({X}^{0}\) is an invisible boson with a mass ranging from 1 to \(260\text{ }\text{ }\mathrm{MeV}/{c}^{2}\). For \({X}^{0}\) with a mass of \(135\text{ }\text{ }\mathrm{MeV}/{c}^{2}\), an upper limit on the branching fraction of \({K}_{L}\rightarrow {\pi }^{0}{X}^{0}\) was set to be \(1.6\times{}{10}^{- 9}\) at the 90% C.L.
Phys. Rev. Lett. 134, 081802 (2025)
Cabibbo-Kobayashi-Maskawa matrix, Electroweak interaction, Flavor changing neutral currents, Leptonic, semileptonic & radiative decays, Rare decays, Kaons, CP symmetry
Wess-Zumino-Witten Interactions of Axions
Research article | Anomalies | 2025-02-26 05:00 EST
Yang Bai, Ting-Kuo Chen, Jia Liu, and Xiaolin Ma
We present a consistent derivation of the complete Wess-Zumino-Witten interactions of axions, including the counter-term necessary to guarantee the gauge invariance of the standard model. By treating the derivative of the axion field as a background gauge field and incorporating auxiliary chiral rotation phases, we ensure consistency in the axion-interaction Lagrangian. This approach allows us to derive basis-independent physical interactions of axions with gauge bosons and vector mesons. These interactions have broad applications in axion phenomenology for both light and heavy axion particles.
Phys. Rev. Lett. 134, 081803 (2025)
Anomalies, Axions, Particle interactions, Phenomenology, Axion-like particles
Dual-Baseline Search for Active-to-Sterile Neutrino Oscillations in NOvA
Research article | Neutrino oscillations | 2025-02-26 05:00 EST
M. A. Acero et al. (NOvA Collaboration)
et al.A comparison of neutrinos measured 1 km and 810 km from their source finds no evidence of a putative fourth neutrino flavor.
Phys. Rev. Lett. 134, 081804 (2025)
Neutrino oscillations, Sterile neutrinos, Neutrino detection
Anisotropic Flow in Fixed-Target \(^{208}\mathrm{Pb}+^{20}\mathrm{Ne}\) Collisions as a Probe of Quark-Gluon Plasma
Research article | Collective flow | 2025-02-26 05:00 EST
Giuliano Giacalone, Wenbin Zhao, Benjamin Bally, Shihang Shen, Thomas Duguet, Jean-Paul Ebran, Serdar Elhatisari, Mikael Frosini, Timo A. Lähde, Dean Lee, Bing-Nan Lu, Yuan-Zhuo Ma, Ulf-G. Meißner, Govert Nijs, Jacquelyn Noronha-Hostler, Christopher Plumberg, Tomás R. Rodríguez, Robert Roth, Wilke van der Schee, Björn Schenke, Chun Shen, and Vittorio Somà
The System for Measuring Overlap with Gas (SMOG2) at the LHCb detector enables the study of fixed-target ion-ion collisions at relativistic energies (\(\sqrt{ {s}_{\mathrm{NN}}}\sim 100\text{ }\text{ }\mathrm{GeV}\) in the center of mass). With input from ab initio calculations of the structure of \(^{16}\mathrm{O}\) and \(^{20}\mathrm{Ne}\), we compute \(3+1\mathrm{D}\) hydrodynamic predictions for the anisotropic flow of \(\mathrm{Pb}+\mathrm{Ne}\) and \(\mathrm{Pb}+\mathrm{O}\) collisions to be tested with upcoming LHCb data. This will allow the detailed study of quark-gluon plasma formation as well as experimental tests of the predicted nuclear shapes. Elliptic flow (\({v}_{2}\)) in \(\mathrm{Pb}+\mathrm{Ne}\) collisions is greatly enhanced compared to the \(\mathrm{Pb}+\mathrm{O}\) baseline due to the shape of \(^{20}\mathrm{Ne}\), which is deformed in a bowling-pin geometry. Owing to the large \(^{208}\mathrm{Pb}\) radius, this effect is seen in a broad centrality range, a unique feature of this collision configuration. Larger elliptic flow further enhances the quadrangular flow (\({v}_{4}\)) of \(\mathrm{Pb}+\mathrm{Ne}\) collisions via nonlinear coupling, and impacts the sign of the kurtosis of the elliptic flow vector distribution (\({c}_{2}{4}\)). Exploiting the shape of \(^{20}\mathrm{Ne}\) proves thus an ideal method to investigate the formation of quark-gluon plasma in fixed-target experiments at LHCb, and demonstrates the power of System for Measuring Overlap with Gas as a tool to image nuclear ground states.
Phys. Rev. Lett. 134, 082301 (2025)
Collective flow, Quark-gluon plasma, Relativistic heavy-ion collisions
Generalized Thermodynamic Relations for Perfect Spin Hydrodynamics
Hydrodynamic models | 2025-02-26 05:00 EST
Wojciech Florkowski and Mykhailo Hontarenko
Generalized thermodynamic relations are introduced into the framework of a relativistic perfect spin hydrodynamics. They allow for consistent treatment of spin degrees of freedom, including the use of spin tensors whose structure follows from microscopic calculations. The obtained results are important for establishing consistency between different formulations of spin hydrodynamics and form the basis for introducing dissipative corrections.
Phys. Rev. Lett. 134, 082302 (2025)
Hydrodynamic models, Relativistic heavy-ion collisions
Room Temperature Superfluorescence from an Electron-Hole Liquid
Research article | Light-matter interaction | 2025-02-26 05:00 EST
Naresh Aggarwal, Ajay Kumar Poonia, Dmitry N. Dirin, Ihor Cherniukh, Arijit Sinha, Umesh V. Waghmare, Maryna I. Bodnarchuk, Sebastian Wüster, Maksym V. Kovalenko, and K. V. Adarsh
Superfluorescence, a coherent burst of light from an excited ensemble of emitters, is a crucial quantum optical phenomenon with far-reaching implications in nanophotonics and many-body optical processes. Despite its observation in various systems, realizing superfluorescence in an electron-hole plasma (EHP) at room temperature has remained a formidable challenge, hindering the development of continuous-wave and electrically excited superfluorescence devices. Herein, we address this challenge by condensing the high-density EHP into an electron-hole liquid (EHL) at room temperature, thereby preserving quantum coherence. Using a model system of nanocrystal thin films, we demonstrate the first experimental observation of room temperature superfluorescence from an EHL. Key attributes heralding superfluorescence include a redshift of \(\sim 94\text{ }\text{ }\mathrm{meV}\) from uncorrelated exciton emission, a fluence-dependent delayed growth of macroscopic coherence with abrupt radiative decay \(\sim 1250\) times faster than spontaneous emission, a distinct quadratic fluence dependence with a clear threshold, and Burnham-Chiao ringing. These findings open up exciting possibilities for developing electrically pumped colloidal nanocrystals lasers and quantum technologies operating at room temperature.
Phys. Rev. Lett. 134, 083801 (2025)
Light-matter interaction, Photonics, Spontaneous emission, Ultrafast phenomena, Quantum dots
\(\mathrm{Q}\)-Plates: From Optical Vortices to Optical Skyrmions
Research article | Optical vortices | 2025-02-26 05:00 EST
Vagharshak Hakobyan and Etienne Brasselet
We report on the extension of the q-plate concept, a hallmark of spin-orbit optical vortex generation since its introduction in 2006, to the generation of optical skyrmions. Stokes skyrmions of arbitrary order with polarization-controlled Skyrme number and reconfigurable multiskyrmions are obtained. This is done by endowing q-plates with a winding number associated with the radial degree of freedom that adds to the usual one associated with the azimuthal degree of freedom.
Phys. Rev. Lett. 134, 083802 (2025)
Optical vortices, Skyrmions, Structured light
Weakly Dispersive Band in Synthetic Moir'e Superlattice Inducing Optimal Compact Comb Generation
Research article | Electro-optic effects | 2025-02-26 05:00 EST
Guangzhen Li, Yanyan He, Luojia Wang, Yiwen Yang, Danying Yu, Yuanlin Zheng, Luqi Yuan, and Xianfeng Chen
The moir'e superlattices attract growing interest for holding exotic physics due to their fascinating properties from electronics to photonics. Much attention has been focused on the localization effect for waves in the flat band regime or the delocalization effect from the strongly dispersive band feature. Here, we study the weakly dispersive band in between the two above scenarios in a one-dimensional synthetic frequency moir'e superlattice and observe the wave packet distributions therein toward novel frequency comb generation. Mode spacing in the spectral wave packet is reduced compared to the free spectral range of individual rings due to the mode couplings from the unequal sublattice periods of the synthetic moir'e lattice. We unveil that the optimal compact frequency comb generation occurs in the weakly dispersive regime holding simultaneously uniform power distribution and broad frequency spanning in our experiment, benefiting from the interplay between the band flatness and power uniformity of mode distribution. Our results study the fundamental physics of the weakly dispersive moir'e band in the synthetic frequency dimension and also show a new way for the future compact frequency comb generation in on-chip devices with small footprint size.
Phys. Rev. Lett. 134, 083803 (2025)
Electro-optic effects, Frequency combs & self-phase locking, Coupled oscillators, Optical fibers, Cavity resonators, Whispering gallery mode resonators
Origin of Nonlinear Circular Photocurrent in 2D Semiconductor \({\mathrm{MoS}}_{2}\)
Research article | Photogalvanic effect | 2025-02-26 05:00 EST
Yanchong Zhao, Fengyu Chen, Jing Liang, Mohammad Saeed Bahramy, Mingwei Yang, Yao Guang, Xiaomei Li, Zheng Wei, Jian Tang, Jiaojiao Zhao, Mengzhou Liao, Cheng Shen, Qinqin Wang, Rong Yang, Kenji Watanabe, Takashi Taniguchi, Zhiheng Huang, Dongxia Shi, Kaihui Liu, Zhipei Sun, Ji Feng, Luojun Du, and Guangyu Zhang
Nonlinear photogalvanic effects in two-dimensional materials, particularly the nonlinear circular photocurrents (NCPs) that belong to the helicity-dependent spin photocurrents, have sparked enormous research interest. Although notable progress has been witnessed, the underling origin of NCPs remains elusive. Here, we present systematic photocurrent characteristics, symmetry analysis and theoretical calculations to uncover the physical origin of NCPs in \({\mathrm{MoS}}_{2}\), a prototypical 2D semiconductor. Our results show that the NCP responses in 2D semiconductor \({\mathrm{MoS}}_{2}\) result from the circular photon drag effect (CPDE), rather than the generally believed circular photogalvanic effect. Furthermore, we demonstrate that the NCPs are highly tunable with electrostatic doping and increase progressively with \({\mathrm{MoS}}_{2}\) thickness, evidencing the interlayer constructive nature of CPDE responses. Our Letter unravels the critical role of the previously overlooked CPDE contribution to NCPs, revolutionizing previous understanding and thus providing deep insights into further fundamental studies and technological advances in nonlinear photovoltaic and opto-spintronic devices.
Phys. Rev. Lett. 134, 086201 (2025)
Photogalvanic effect, Second order nonlinear optical processes, Transition metal dichalcogenides, First-principles calculations
Orbital Competition in Bilayer Graphene's Fractional Quantum Hall Effect
Research article | Anyons | 2025-02-26 05:00 EST
Bishoy M. Kousa, Nemin Wei, and Allan H. MacDonald
The lowest Landau level of bilayer graphene has an octet of internal degrees of freedom, composed from spin, valley, and orbital two-level systems. Dominance of \(n=0\) orbitals over \(n=1\) orbitals in low energy quantum fluctuations leads to distinct fractional quantum Hall characteristics compared dominance of \(n=1\) over \(n=0\). The competition between \(n=0\) and \(n=1\) orbitals depends sensitively on particle-hole asymmetry in the single-particle Hamiltonian and on Lamb shifts due to exchange interactions with the negative energy sea, which must be accounted for simultaneously in assessing the orbital competition. We identify the circumstances under which \(n=1\), which supports strong even-denominator fractional quantum Hall states with non-Abelian quasiparticles, emerges robustly as the low-energy Landau level.
Phys. Rev. Lett. 134, 086502 (2025)
Anyons, Fractionalization, Landau levels, Quantum Hall effect, Bilayer graphene, Hartree-Fock methods
Magnetic Lyddane-Sachs-Teller Relation
Research article | Magnetic susceptibility | 2025-02-26 05:00 EST
Viktor Rindert, Vanya Darakchieva, Tapati Sarkar, and Mathias Schubert
A new formula that connects a material's magnetic permeability to spin dynamics has been derived and tested 84 years after the debut of its electric counterpart.
Phys. Rev. Lett. 134, 086703 (2025)
Magnetic susceptibility, Magneto-optics, Electron paramagnetic resonance, Terahertz spectroscopy
Four-Wave Mixing at peV Energy Scales
Research article | Spin dynamics | 2025-02-26 05:00 EST
C. Simon, D. M. Silevitch, and T. F. Rosenbaum
We measure the nonlinear magnetic susceptibility \({\chi }^{(3)}\) of the disordered quantum Ising magnet \({\mathrm{LiHo}}_{0.045}{\mathrm{Y}}_{0.955}{\mathrm{F}}_{4}\) and demonstrate four-wave mixing due to coherent (anti-)Stokes Raman scattering at \(\sim 100\text{ }\text{ }\mathrm{Hz}\) (peV) energy scales. The temperature dependence of \({\chi }^{(3)}\) approximately follows a \((1/T)\) form, with a high-\(T\) cutoff that can be linked to dissipation in the coherent spin clusters. \({\chi }^{(3)}\) also decreases monotonically with a transverse field, approaching a constant offset above a few kOe, suggesting the presence of both coherent and spontaneous Raman scattering.
Phys. Rev. Lett. 134, 086705 (2025)
Spin dynamics, Rare-earth magnetic materials, AC susceptibility measurements, Four-wave mixing
Mediation of Colloidal Encounter Dynamics by Surface Roughness
Research article | Fluid-particle interactions | 2025-02-26 05:00 EST
Robert G. Felsted, Jaehun Chun, Gregory K. Schenter, Alexander B. Bard, Xiaojing Xia, and Peter J. Pauzauskie
Rigorous understanding of assembly in colloidal systems is crucial to the development of tailored nanostructured materials. Despite extensive studies, a mechanistic understanding of the dynamics governing encounters of colloidal particles remains an ongoing challenge. We study colloidal encounter dynamics by inducing assembly through optical tweezers that impose an external attractive field for cubic-phase sodium yttrium fluoride nanocrystals. We show that surface roughness of the nanocrystals is a decisive factor for contact leading to assembly between the nanocrystals, manifested by the roughness-dependent hydrodynamic resistivity. This provides direct evidence that dynamics are equally important to energetics in understanding assembly.
Phys. Rev. Lett. 134, 088201 (2025)
Fluid-particle interactions, Roughness, Self-assembly, Colloids, Hydrodynamics, Langevin equation, Optical tweezers
Beyond Dipolar Activity: Quadrupolar Stress Drives Collapse of Nematic Order on Frictional Substrates
Research article | Biomimetic & bio-inspired materials | 2025-02-26 05:00 EST
Aleksandra Ardaševa, Ignasi Vélez-Cerón, Martin Cramer Pedersen, Jordi Ignés-Mullol, Francesc Sagués, and Amin Doostmohammadi
The field of active nematics has traditionally employed descriptions based on dipolar activity. However, it is theoretically predicted that interactions with a substrate, prevalent in most biological systems, lead to novel forms of activity, such as quadrupolar activity, that are governed by hydrodynamic screening. Here, combining experiments and numerical simulations, we show that upon light-induced solidification of the underlying medium, microtubule-kinesin mixtures undergo a transformation that leads to a biphasic active suspension. Using an active lyotropic model, we prove that the transition is governed by screening effects that alter the dominant form of active stress. Specifically, the combined effect of friction and quadrupolar activity leads to a hierarchical folding that follows the intrinsic bend instability of the active nematic layer. Our results demonstrate the dynamics of the collapse of orientational order in active nematics and present a new route for controlling active matter by modifying the activity through changing the surrounding environment.
Phys. Rev. Lett. 134, 088301 (2025)
Biomimetic & bio-inspired materials, Functional materials, Living matter & active matter, Lyotroptic active nematics
Erratum: Emergent \(\mathrm{Sp}(3,\mathbb{R})\) Dynamical Symmetry in the Nuclear Many-Body System from an Ab Initio Description [Phys. Rev. Lett. 125, 102505 (2020)]
Correction | | 2025-02-26 05:00 EST
Anna E. McCoy, Mark A. Caprio, Tomáš Dytrych, and Patrick J. Fasano
Phys. Rev. Lett. 134, 089901 (2025)
Physical Review X
Light-Induced Reorientation Transition in an Antiferromagnetic Semiconductor
Research article | Dynamical phase transitions | 2025-02-26 05:00 EST
Bryan T. Fichera, Baiqing Lv, Karna Morey, Zongqi Shen, Changmin Lee, Elizabeth Donoway, Alex Liebman-Peláez, Anshul Kogar, Takashi Kurumaji, Martin Rodriguez-Vega, Rodrigo Humberto Aguilera del Toro, Mikel Arruabarrena, Batyr Ilyas, Tianchuang Luo, Peter Müller, Aritz Leonardo, Andres Ayuela, Gregory A. Fiete, Joseph G. Checkelsky, Joseph Orenstein, and Nuh Gedik
A demonstration of ultrafast optical manipulation of antiferromagnetic order in CaMn2Bi2 reveals a metastable spin state that persists for more than 150 ps, paving the way for advanced spintronic and ultrafast magnetic-device technologies.
Phys. Rev. X 15, 011044 (2025)
Dynamical phase transitions, Light-induced magnetic effects, Magnetic order, Magnetic phase transitions, Order parameters, Spintronics, Ultrafast magnetic effects, Ultrafast phenomena, Nonequilibrium systems, Strongly correlated systems, Optical second-harmonic generation, Ultrafast pump-probe spectroscopy
arXiv
Theory of Nonlinear Spectroscopy of Quantum Magnets
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-02-26 20:00 EST
Anubhav Srivastava, Stefan Birnkammer, GiBaik Sim, Michael Knap, Johannes Knolle
Two-dimensional coherent spectroscopy (2DCS) is an established method for characterizing molecules and has been proposed in the THz regime as a new tool for probing exotic excitations of quantum magnets; however, the precise nature of the coupling between pump field and spin degrees of freedom has remained unclear. Here, we develop a general response theory of 2DCS and show how magneto-electric as well as polarization couplings contribute to 2DCS in addition to the typically assumed magnetization. We propose experimental protocols to distill individual contributions, for instance from exchange-striction or spin current mechanism, when the electric field couples to terms quadratic in spin operators. We provide example calculations for the paradigmatic twisted Kitaev chain material \(\mathrm{CoNb}_{2}\mathrm{O}_{6}\) and highlight the crucial role of contributions from cross-coupling between polarization and magnetic nonlinear susceptibilities. Our work paves the way for systematic studies of light-matter couplings in quantum magnets and for establishing 2DCS as a versatile tool for probing fractional excitations of exotic magnetic quantum phases.
Strongly Correlated Electrons (cond-mat.str-el)
16 pages, 9 figures
Quarter Metal Superconductivity
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-02-26 20:00 EST
Chiho Yoon, Tianyi Xu, Yafis Barlas, Fan Zhang
We investigate the recently discovered multiple superconducting states in rhombohedral graphene quarter metal. We demonstrate that one of these states features a single-spin, single-valley, single-band, single-Fermi-pocket parent state and is most likely a chiral topological pair-density wave, marked by a threefold symmetry that may not be spontaneously broken, unpaired Majorana zero modes at edges, vortices, and dislocations, and an anomalous intrinsic superconducting diode effect.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Strongly Correlated Electrons (cond-mat.str-el), Superconductivity (cond-mat.supr-con)
7+2 pages, 3+3 figures
Shining light on collective modes in moiré fractional Chern insulators
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-02-26 20:00 EST
Nisarga Paul, Ahmed Abouelkomsan, Aidan Reddy, Liang Fu
We show that collective excitations and optical responses of moiré fractional Chern insulators (FCIs) drastically differ from those of standard fractional quantum Hall (FQH) states in a Landau level. By constructing a variational wavefunction that incorporates the moiré lattice effect, we capture the collective modes in FCIs across a range of crystal momenta including the roton minimum. Interestingly, new collective modes -- ``fractional excitons'' -- are found in the long wavelength limit (\(\boldsymbol{q} \rightarrow 0\)) at low energy below the excitation continuum, distinct from the FQH case. Some of these modes are optically active and manifest as sharp peaks in optical conductivity at THz frequency. We further show that intraband optical absorption and spectral weight in twisted \({\rm MoTe}_2\) are highly tunable by the displacement field. Our work thus establishes optical spectroscopy as a powerful tool to illuminate the unique collective modes of moiré FCIs.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Strongly Correlated Electrons (cond-mat.str-el)
5 + 11 pages , 2 + 6 figures
Theory of magnetoroton bands in moiré materials
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-02-26 20:00 EST
Bishoy M. Kousa, Nicolás Morales-Durán, Tobias M. R. Wolf, Eslam Khalaf, Allan H. MacDonald
The recent realizations of the Hofstadter butterfly and fractional Chern insulators in moiré materials have introduced a new ingredient, a periodic lattice potential, to the study of quantum Hall phases. While the fractionalized states in moiré systems are expected to be in the same universality class as their counterparts in Landau levels, the periodic potential can have qualitative and quantitative effects on physical observables. Here, we examine how the magnetoroton collective modes of fractional quantum Hall (FQH) states are altered by external periodic potentials. Employing a single-mode-approximation, we derive an effective Hamiltonian for the low-energy neutral excitations expressed in terms of three-point density correlation functions, which are computed using Monte Carlo. Our analysis is applicable to FQH states in graphene with a hexagonal boron nitride (hBN) substrate and also to fractional Chern insulator (FCI) states in twisted MoTe\(_2\) bilayers. We predict experimentally testable trends in the THz absorption characteristics of FCI and FQH states and estimate the external potential strength at which a soft-mode phase transition occurs between FQH and charge density wave (CDW) states.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Strongly Correlated Electrons (cond-mat.str-el)
11 pages, 5 figures
On the Electronic Structure of Kagome metals \(A\)V\(_3\)Sb\(_5\)
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-02-26 20:00 EST
Keyu Zeng, Zhan Wang, Kun Jiang, Ziqiang Wang
The kagome metals \(A\)V\(_3\)Sb\(_5\) (\(A=\) K, Cs, Rb) have become a fascinating materials platform following the discovery of many novel quantum states due to the interplay between electronic correlation, topology, and geometry. Understanding their physical origin requires constructing effective theories that capture the low-energy electronic structure and electronic interactions. While the band structure calculated by density functional theory (DFT) broadly agrees with experiments in the unbroken symmetry phase, the multiorbital nature challenges a proper understanding of the band structure and its description by tight-binding models. Here, we point out the unusual and puzzling properties of the DFT electronic structure, including the sublattice type of the van Hove singularities, the geometric shape of the Fermi surface, and the orbital content of the low-energy band dispersion, which cannot be described by the commonly used one-orbital or multiorbital kagome tight-binding models. We address these fundamental puzzles and develop an extended Slater-Koster formalism that can successfully resolve these issues. We discover the important role of site-symmetry and interorbital hopping structure and provide a concrete multiorbital tight-binding model description of the electronic structure for \(A\)V\(_3\)Sb\(_5\) and the family of ``135'' compounds with other transition metals. This is a crucial step toward studying the effects of electron-electron interactions for the correlated and topological states in kagome metals and superconductors.
Strongly Correlated Electrons (cond-mat.str-el), Materials Science (cond-mat.mtrl-sci)
14 pages, 9 figures
Developing fractional quantum Hall states at even-denominator fillings 1/6 and 1/8
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-02-26 20:00 EST
Chengyu Wang, P. T. Madathil, S. K. Singh, A. Gupta, Y. J. Chung, L. N. Pfeiffer, K. W. Baldwin, M. Shayegan
In the extreme quantum limit, when the Landau level filling factor \(\nu<1\), the dominant electron-electron interaction in low-disorder two-dimensional electron systems leads to exotic many-body phases. The ground states at even-denominator \(\nu=\) 1/2 and 1/4 are typically Fermi seas of composite fermions carrying two and four flux quanta, surrounded by the Jain fractional quantum Hall states (FQHSs) at odd-denominator fillings \(\nu=p/(2p\pm1)\) and \(\nu=p/(4p\pm1)\), where \(p\) is an integer. For \(\nu<\) 1/5, an insulating behavior, which is generally believed to signal the formation of a pinned Wigner crystal, is seen. Our experiments on ultrahigh-quality, dilute, GaAs two-dimensional electron systems reveal developing FQHSs at \(\nu=p/(6p\pm1)\) and \(\nu=p/(8p\pm1)\), manifested by magnetoresistance minima superimposed on the insulating background. In stark contrast to \(\nu=\) 1/2 and 1/4, however, we observe a pronounced, sharp minimum in magnetoresistance at \(\nu=\) 1/6 and a somewhat weaker minimum at \(\nu=\) 1/8, suggesting developing FQHSs, likely stabilized by the pairing of composite fermions that carry six and eight flux quanta. Our results signal the unexpected entry, in ultrahigh-quality samples, of FQHSs at even-denominator fillings 1/6 and 1/8, which are likely to harbor non-Abelian anyon excitations.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Strongly Correlated Electrons (cond-mat.str-el)
7+20 pages, 3+14 figures
Phys. Rev. Lett. 134, 046502 (2025)
Mesoscale Modeling of an Active Colloid's Motion
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-02-26 20:00 EST
This paper uses Cahn-Hilliard equations as a mesoscale model of the motion of active colloids. The model attempts to capture the driving mechanisms and qualitative behavior of the isotropic colloids originally proposed by J. Decayeaux in 2021. We compare our model against the single colloid behavior presented in that work, as well as against multi-colloid systems.
Soft Condensed Matter (cond-mat.soft), Numerical Analysis (math.NA)
11 pages, 7 figures
Spin relaxation and transport behaviors in altermagnetic systems
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-02-26 20:00 EST
The D'yakonov-Perel' (DP) spin-relaxation mechanism has traditionally been associated with either relativistic spin-orbit coupling, which breaks space-inversion symmetry, or inhomogeneous magnetization, which breaks both time-reversal and translational symmetries. Here, we investigate spin relaxation mechanism in altermagnetic systems which possess novel magnetic states characterized by sublattices connected through crystal-rotation symmetries and opposite spins with zero overall net magnetization and absence of spin-orbit coupling. We find that altermagnetic states exhibit DP-type spin relaxations in both strong- and weak-scattering regimes, with the spin relaxation rate decreasing to zero as the temperature approaches the critical temperature of the altermagnetic phase transition. However, the scattering time involved in this spin relaxation mechanism is not the momentum relaxation time, in contrast to the conventional DP spin relaxation. Using a kinetic approach incorporating rigorous microscopic scattering, we demonstrate that the spin Hall current is highly anisotropic and proportional to the degree of altermagnetic order.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci)
9 pages, 5 figures
Hole Spin in Direct Bandgap Germanium-Tin Quantum Dot
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-02-26 20:00 EST
Nicolas Rotaru, Patrick Del Vecchio, Oussama Moutanabbir
Germanium (Ge) has emerged as a contender for scalable solid-state spin qubits. This interest stems from the numerous attractive properties of hole spin in Ge low-dimensional systems and their compatibility with the standards of silicon processing. Herein, we show that the controlled incorporation of Sn into the Ge lattice enables hole spin quantum dots that retain the same advantages as those made of Ge while also providing bandgap directness. The latter is essential for a more efficient interaction with light, a key feature in the implementation of photon-spin interfaces and quantum memories. We first map the material properties for a range of Ge\(_{1-x}\)Sn\(_x\) planar heterostructures to identify the optimal conditions to simultaneously achieve hole spin confinement and bandgap directness. Although compressive strain is necessary for heavy hole confinement, we estimate that an additional 4.5 at.% of Sn is needed for every 1% increase in the absolute value of compressive strain to preserve the direct bandgap. However, a high compressive strain is found to be detrimental to the Rashba coupling. Moreover, a theoretical framework is derived to evaluate the dipole moment \(d\) and the relaxation rate \(\Gamma\) of electric dipole spin resonance quantum dot devices. We compare the perturbative and effective values of \(d\) with the values obtained from the full 3D Hamiltonian. We find \(d\) to be around 1 and 0.01 e pm for the out-of-plane and in-plane configurations, respectively, and \(\Gamma\propto B^5\), eventually becoming \(\propto B^7\) in the out-of-plane configuration.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
14 pages, 5 figures
Microscopic Theory of Chern Polarization
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-02-26 20:00 EST
Thivan M. Gunawardana, Frank Schindler, Ari M. Turner, Ryan Barnett
The modern theory of polarization does not apply in its original form to systems with non-trivial band topology. Chern insulators are one such example since they are insulating in the bulk but exhibit metallic edge states, complicating the definition of polarization. Wannier functions formed a key ingredient of the original modern theory of polarization, but it has been considered that these cannot be applied to Chern insulators since they are no longer exponentially localized and the Wannier center is no longer gauge invariant. In this Letter, we provide an unambiguous definition of absolute polarization for a Chern insulator in terms of the Zak phase. We obtain our expression by studying the non-quantized fractional charge bound to lattice dislocations and it can be computed directly from bulk quantities and makes no assumption on the edge state filling. Our result is fully consistent with previous results on the quantized charge bound to dislocations in the presence of crystalline symmetry. At the same time, our result is more general since it also applies to Chern insulators which do not have crystalline symmetries other than translations.
Strongly Correlated Electrons (cond-mat.str-el), Quantum Physics (quant-ph)
5+5 pages, 2+3 figures
First-principles Investigation of Exceptional Coarsening-resistant V-Sc(Al2Cu)4 Nanoprecipitates in Al-Cu-Mg-Ag-Sc Alloys
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-26 20:00 EST
Junyuan Bai, Hao Xue, Jiaming Li, Xueyong Pang, Zhihao Zhao, Gang Liu, Gaowu Qin
Aluminum-copper-magnesium-sliver (Al-Cu-Mg-Ag) alloys are extensively utilized in aerospace industries due to the formation of Omega this http URL, the rapid coarsening of these nano-plates above 475 K restricts their application at elevated this http URL introducing scandium (Sc) to these alloys, the service temperature of the resultant alloys can reach an unprecedented 675 K, attributed to the in situ formation of a coarsening-resistant V-Sc(Al2Cu)4 phase within the Omega nano-plates. However, the fundamental thermodynamic properties and mechanisms behind the remarkable coarsening resistance of V nano-plates remain this http URL, we employ first-principles calculations to investigate the phase stability of V-Sc(Al2Cu)4 phase, the basic kinetic features of V phase formation within Omega nano-plates, and the origins of the extremely high thermal stability of V nano-plates. Our results indicate that V-Sc(Al2Cu)4 is meta-stable and thermodynamically tends to evolve into a stable ScAl7Cu5 phase. We also demonstrate that kinetic factors are mainly responsible for the temperature dependence of V phase formation. Notably, the formation of V-Sc(Al2Cu)4 within Omega nano-plates modifies the Kagome lattice in the shell layer of the Omega nano-plates, inhibiting further thickening of V nano-plates through the thickening pathway of Omega nano-plates. This interface transition leads to the exceptional coarsening resistance of the V nano-plates. Moreover, we also screened 14 promising element substitutions for Sc. These findings are anticipated to accelerate the development of high-performance Al alloys with superior heat resistance.
Materials Science (cond-mat.mtrl-sci)
Atomic layer etching of niobium nitride using sequential exposures of O\(_2\) and H\(_2\)/SF\(_6\) plasmas
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-26 20:00 EST
Azmain A. Hossain, Sela Murphy, David S. Catherall, Anthony J. Ardizzi, Austin J. Minnich
Niobium nitride (NbN) is a metallic superconductor that is widely used for superconducting electronics due to its high transition temperature (\(T_c\)) and kinetic inductance. Processing-induced damage negatively affects the performance of these devices by mechanisms such as microwave surface loss. Atomic layer etching (ALE), with its ability to etch with Angstrom-scale control and low damage, has the potential to address these issues, but no ALE process is known for NbN. Here, we report such a process consisting of sequential exposures of O\(_2\) plasma and H\(_2\)/SF\(_6\) plasma. Exposure to O\(_2\) plasma rather than O\(_2\) gas yields a greater fraction of Nb in the +5 oxidation state, which is then volatilized by NbF\(_5\) formation with exposure to an H\(_2\)/SF\(_6\) plasma. The SF\(_6\):H\(_2\) flow rate ratio is chosen to produce selective etching of Nb\(_2\)O\(_5\) over NbN, enabling self-limiting etching within a cycle. An etch rate of 1.77 Å/cycle was measured at 125 \(^\circ\)C using ex-situ ellipsometry. The \(T_c\) of the ALE-etched film is higher than that of an RIE-etched film of a similar thickness, highlighting the low-damage nature of the process. These findings have relevance for applications of NbN in single-photon detectors and superconducting microresonators.
Materials Science (cond-mat.mtrl-sci), Superconductivity (cond-mat.supr-con)
16 pages, 8 figures
Ductility mechanisms in complex concentrated refractory alloys from atomistic fracture simulations
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-26 20:00 EST
Wenqing Wang, Punit Kumar, David H. Cook, Flynn Walsh, Buyu Zhang, Pedro P.P.O. Borges, Diana Farkas, Robert O. Ritchie, Mark Asta
The striking variation in damage tolerance among refractory complex concentrated alloys is examined through the analysis of atomistic fracture simulations, contrasting behavior in elemental Nb with that in brittle NbMoTaW and ductile Nb45Ta25Ti15Hf15. We employ machine-learning interatomic potentials (MLIPs), including a new MLIP developed for NbTaTiHf, in atomistic simulations of crack tip extension mechanisms based on analyses of atomistic fracture resistance curves. While the initial behavior of sharp cracks shows good correspondence with the Rice theory, fracture resistance curves reveal marked changes in fracture modes for the complex alloys as crack extension proceeds. In NbMoTaW, compositional complexity appears to promote dislocation nucleation relative to pure Nb, despite theoretical predictions that the alloy should be relatively more brittle. In Nb45Ta25Ti15Hf15, alloying not only changes the fracture mode relative to elemental Nb, but promotes dislocation accumulation at the crack tip, leading to higher resistance to crack propagation.
Materials Science (cond-mat.mtrl-sci)
Swirling topological textures of polarization in bulk relaxor ferroelectrics
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-26 20:00 EST
M. Eremenko, V. Krayzman, S. Gorfman, A. Bosak, H. Y. Playford, P. A. Chater, B. Ravel, W. J. Laws, F. Ye, A. Minelli B.-X. Wang, Z-G. Ye, M. G. Tucker, I. Levin
A complete understanding of the mechanisms for dielectric relaxation in relaxor ferroelectrics remains elusive. We used a structural refinement framework that integrates several types of experimental data to identify the nanoscale correlations of polarization and their relationship to the underlying chemistry in the classic relaxor system PbMg1/3Nb2/3O3-PbTiO3. The polar structure in these materials in their bulk cubic state can be represented as overlapping anisotropic volumes, each encompassing unit cells with projections of their polarization vectors onto the volume's longest axis pointing in the same direction. The overlap results in swirling topological textures of polarization containing vortices, such as merons, and displaying smooth changes in the polarization directions. The locations of these vortices are linked to the electric charge gradient caused by compositional heterogeneities, deemed to create depolarizing fields.
Materials Science (cond-mat.mtrl-sci)
Controlling spin currents with magnon interference in a canted antiferromagnet
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-02-26 20:00 EST
Lutong Sheng, Anna Duvakina, Hanchen Wang, Kei Yamamoto, Rundong Yuan, Jinlong Wang, Peng Chen, Wenqing He, Kanglin Yu, Yuelin Zhang, Jilei Chen, Junfeng Hu, Song Liu, Xiufeng Han, Dapeng Yu, Jean-Philippe Ansermet, Sadamichi Maekawa, Dirk Grundler, Haiming Yu
Controlling spin current lies at the heart of spintronics and its applications. The sign of spin currents is monotonous in ferromagnets once the current direction is determined. Spin currents in antiferromagnets can possess opposite polarization, but requires enormous magnetic fields to lift the degeneracy. Controlling spin currents with different polarization is urgently demanded but remains hitherto elusive. Here, we demonstrate the control of spin currents at room temperature by magnon interference in a canted antiferromagnet, hematite recently also classified as an altermagnet. Magneto-optical characterization by Brillouin light scattering revealed that the spatial periodicity of the beating patterns was tunable via the microwave frequency. The inverse spin-Hall voltage changed sign as the frequency was scanned, i.e., a frequency-controlled switching of polarization in pure spin currents was obtained. Our work marks the use of antiferromagnetic magnon interference to control spin currents, which substantially extends the horizon for the emerging field of coherent antiferromagnetic spintronics.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Quantum Transport in Reduced Graphene Oxide Measured by Scanning Probe Microscopy
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-02-26 20:00 EST
Julian Sutaria, Cristian Staii
We report combined scanning probe microscopy and transport measurements to investigate the local electronic transport properties of reduced graphene oxide (rGO) devices. We demonstrate that the quantum transport properties in these materials can be significantly tuned by the electrostatic potential applied by an atomic force microscope (AFM) conducting tip. Scanning gate microscopy measurements show a distinct p-type response, where the AFM tip locally gates the rGO, thereby modulating the transport current. Additional scanning impedance microscopy measurements indicate shifts in the Fermi energy under different gating conditions, highlighting the strong influence of local electrostatic potentials on the transport characteristics of rGO. We demonstrate that the interplay between the tip-induced Fermi level shifts and defect-mediated scattering processes plays a key role in determining the observed transport behavior. Our findings emphasize the crucial role of scattering mechanisms, particularly resonant scattering caused by impurities or structural defects, in determining low-dimensional transport behavior in rGO. Notably, rGO exhibits resonant scattering effects akin to those seen in one-dimensional systems like carbon nanotubes, despite its two-dimensional structure. These insights advance our current understanding of charge transport in rGO, and have important implications for its use in nanoscale electronics, flexible sensors, and tunable optoelectronic devices.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci), Strongly Correlated Electrons (cond-mat.str-el), Quantum Physics (quant-ph)
7 pages, 4 figures
Ultralow-temperature ultrafast synthesis of wafer-scale single-crystalline graphene via metal-assisted graphitization of silicon-carbide
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-26 20:00 EST
Se H. Kim, Hanjoo Lee, Dong Gwan Kim, Donghan Kim, Seugki Kim, Hyunho Yang, Yunsu Jang, Jangho Yoon, Hyunsoo Kim, Seoyong Ha, ByoungTak Lee, Jung-Hee Lee, Roy Byung Kyu Chung, Hongsik Park, Sungkyu Kim, Tae Hoon Lee, Hyun S. Kum
Non-conventional epitaxial techniques, such as vdWE and remote epitaxy, have attracted substantial attention in the semiconductor research community for their exceptional capability to continuously produce high-quality free-standing films. The successful implementation of these emerging epitaxial techniques crucially hinges on creating a robust uniform 2D material surface at the wafer-scale and with atomically precise uniformity. The conventional method for fabricating graphene on a SiC wafer is through high-temperature graphitization, which produces epitaxial graphene on the surface of the SiC wafer. However, the extremely high temperature needed for silicon sublimation (> 1500 C) causes step-bunching of the SiC surface in addition to the growth of uneven graphene at the edges of the step, leading to multilayer graphene stripes and unfavorable surface morphology for epitaxial growth. Here, we fully develop a graphitization technique that allows fast synthesis of single-crystalline graphene at ultra-low temperatures (growth time of less than 1 min and growth temperature of less than 500 C) at wafer-scale by metal-assisted graphitization. We found annealing conditions that enable SiC dissociation while avoiding silicide formation, which produces single-crystalline graphene while maintaining atomically smooth surface morphology. The thickness of the graphene layer can be precisely controlled by varying the metal thickness or annealing temperature. We successfully produce freestanding single-crystalline ultra-wide bandgap (AlN, GaN) films on graphene/SiC via the 2D material-based layer transfer technique. Our results show that low-temperature graphene synthesis via MAG represents a promising route for the commercialization of the 2D-based epitaxy technique, enabling the production of large-scale ultra-wide bandgap free-standing crystalline membranes.
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Incongruent Melting and Phase Diagram of SiC from Machine Learning Molecular Dynamics
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-26 20:00 EST
Yu Xie, Senja Ramakers, Menghang Wang, Frans Spaepen, Boris Kozinsky
Silicon carbide (SiC) is an important technological material, but its high-temperature phase diagram has remained unclear due to conflicting experimental results about congruent versus incongruent melting. Here, we employ large-scale machine learning molecular dynamics (MLMD) simulations to gain insights into SiC decomposition and phase transitions. Our approach relies on a Bayesian active learning workflow to efficiently train an accurate machine learning force field on density functional theory data. Our large-scale simulations provide direct evidence of the incongruent melting of SiC, confirming its decomposition into silicon-rich and carbon phases at high temperature and pressure. During cooling at high pressures, carbon nanoclusters nucleate and grow within the homogeneous molten liquid. During heating, the decomposed mixture reversibly transitions back into a homogeneous SiC liquid. The full pressure-temperature phase diagram of SiC is systematically constructed using MLMD simulations, providing new understanding of the nature of phases, resolving long-standing inconsistencies from previous experiments and yielding technologically relevant implications for processing and deposition of this material.
Materials Science (cond-mat.mtrl-sci)
Colloidal Magnus effect in polymer solutions
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-02-26 20:00 EST
Marco De Corato, Kun Zhang, Lailai Zhu
Rotating particles moving in fluids undergo a transverse migration via the inertia-induced Magnus effect. This phenomenon vanishes at colloidal scales because inertia is negligible and the fluid flow is time reversible. Yet, recent experiments discovered an inverse Magnus effect of colloids in polymeric and micellar solutions supposedly because their viscoelasticity breaks the time reversibility. Our study shows that classical viscoelastic features -- normal-stress differences and/or shear-thinning cannot explain this phenomenon. Instead, it originates from local polymer density inhomogeneities due to their stress-gradient-induced transport, a mechanism increasingly important at smaller scales -- indeed relevant to colloidal experiments. Incorporating this mechanism into our model leads to quantitative agreement with the experiments without fitting parameters. Our work provides new insights into colloidal motion in complex fluids with microstructural inhomogeneities, offers a simple mechanistic theory for predicting the resulting migration, and underscores the necessity of assimilating these findings in future designs of micro-machinery including swimmers, actuators, rheometers, and so on.
Soft Condensed Matter (cond-mat.soft)
Anomalous energy gap in superconducting La\(_{2.85}\)Pr\(_{0.15}\)Ni\(_2\)O\(_7\)/SrLaAlO\(_4\) heterostructures
New Submission | Superconductivity (cond-mat.supr-con) | 2025-02-26 20:00 EST
Jianchang Shen, Yu Miao, Zhipeng Ou, Guangdi Zhou, Yaqi Chen, Runqing Luan, Hongxu Sun, Zikun Feng, Xinru Yong, Peng Li, Yueying Li, Lizhi Xu, Wei Lv, Zihao Nie, Heng Wang, Haoliang Huang, Yu-Jie Sun, Qi-Kun Xue, Zhuoyu Chen, Junfeng He
The discovery of superconductivity in bilayer nickelate thin films under ambient pressure provides an opportunity to directly investigate characteristic energy scales of the superconducting state from electronic structure. Here, we successfully probe the energy gap and dispersion renormalization in one unit-cell La\(_{2.85}\)Pr\(_{0.15}\)Ni\(_2\)O\(_7\) films epitaxially grown on SrLaAlO\(_4\) substrates, by developing an ultra-high vacuum quenching technique for in-situ angle-resolved photoemission spectroscopy measurements. The energy gap is observed on the underlying Fermi surface without showing a node along the Brillouin zone diagonal. This gap exhibits particle-hole symmetric behavior and persists to a temperature higher than the superconducting transition temperature, indicating the existence of a pseudogap. An abrupt band renormalization is observed with a dispersion anomaly at ~70 meV below Fermi level, pointing to another energy scale besides the energy gap. These observations provide initial information on fundamental properties of the superconducting state in bilayer nickelates under ambient pressure.
Superconductivity (cond-mat.supr-con), Strongly Correlated Electrons (cond-mat.str-el)
Probing Mixed Valence States by Nuclear Spin-Spin Relaxation Time Measurements
New Submission | Superconductivity (cond-mat.supr-con) | 2025-02-26 20:00 EST
Yoshihiko Ihara, Masakazu Shimohashi, Markus Kriener
Several elements in the periodic table exhibit an interesting and often overlooked feature: They skip certain valence states which is discussed in the field of superconductivity to be in favor of fostering higher transition temperatures \(T_c\). However, from the experimental point of view, it is often deemed difficult to probe changes in the valence state. Here we demonstrate that the latter are accessible by the spin-spin relaxation rate \(1/T_2\) in nuclear magnetic resonance. As target material, we chose the solid solution Ge\(_{1-x}\)In\(_x\)Te, where valence-skipping In induces superconductivity and changes its valence state as a function of \(x\). We observe a strong enhancement in \(1/T_2(x)\) and, most importantly, find that \(1/T_2\) and \(T_c\) exhibit a strikingly similar \(x\) dependence. These results underline the importance of valence physics for the evolution of superconductivity in Ge\(_{1-x}\)In\(_x\)Te. A model based on a Ruderman-Kittel-Kasuya-Yosida type of interaction among the In nuclei is proposed which fully accounts for the experimental results.
Superconductivity (cond-mat.supr-con)
7 pages, 4 figures (Main text), 11 pages, 4 figures (Supplemental Materials)
Exact mobility edges in quasiperiodic network models with slowly varying potentials
New Submission | Disordered Systems and Neural Networks (cond-mat.dis-nn) | 2025-02-26 20:00 EST
Hai-Tao Hu, Yang Chen, Xiaoshui Lin, Ai-Min Guo, Guangcan Guo, Ming Gong, Zijing Lin
Quasiperiodic potentials without self-duality are always hard to derive the exact mobility edges (MEs). Here, we propose a new class of network models with exactly solvable MEs, characterized by quasiperiodic slowly varying potentials that do not exhibit hidden self-duality. We present two methods to derive the MEs, the first involves integrating out the periodic sites to obtain an effective Hamiltonian with effective potential \(g(E)V\) and effective eigenenergy \(f(E)\), which directly yields the MEs at \(f(E) = \pm(2t\pm g(E)V)\), and the second is to connect the localized-delocalized transition points of the quasiperiodic slowly varying models and the real-complex transition points of the eigenvalue equations. To illustrate this, we take quasiperiodic mosaic slowly varying models as examples, and we find that the MEs obtained from the two methods are the same. Furthermore, we generalize our methods to quasiperiodic network models and propose a possible experimental realization based on optical waveguide systems, showing that the Anderson transition can be observed even using small physical systems (with \(L = 50 - 100\)). Our results may provide insight into understanding and realizing exact MEs in experiments.
Disordered Systems and Neural Networks (cond-mat.dis-nn)
Breathing ferroelectricity induced topological valley states in kagome niobium halide monolayers
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-26 20:00 EST
Kai-Qi Wang, Jun-Ding Zheng, Wen-Yi Tong, Chun-Gang Duan
In recent years, kagome lattices have garnered significant attention for their diverse properties in topology, magnetism, and electron correlations. However, the exploration of breathing kagome lattices, which exhibit dynamic breathing behavior, remains relatively scarce. Structural breathing introduces an additional degree of freedom that is anticipated to fine-tune the electronic structure, potentially leading to exotic properties within the system. In this study, we employ a combination of the kp model and first-principles calculations to explore how breathing ferroelectricity can modulate valley states within a monolayer of niobium halide with breathing kagome lattice. Through the interplay of magnetoelectric coupling and the lock-in between breathing and ferroelectric states, we demonstrate that a dynamically breathing process, when controlled by an appropriately applied electric field, can achieve valley polarization reversal and generate multiple valley states, including those that are topologically nontrivial. These state transformations may couple to distinctive properties in circularly-polarized optical responses and various valley Hall effects. Consequently, our results suggest that materials featuring breathing kagome lattices represent promising platforms for studying the interplay among structure, charge, spin, and valley degrees of freedom, a crucial step toward developing multifunctional devices.
Materials Science (cond-mat.mtrl-sci)
Experimental evidence of Tc enhancement above 50 K and diode and paramagnetic-Meissner effects, in Nickelate films on highly reduced \(SrTiO_3\)
New Submission | Superconductivity (cond-mat.supr-con) | 2025-02-26 20:00 EST
Since the discovery of superconductivity in nickelate thin films in 2019, the quest for enhancing their \(T_c\) has been ongoing. Here we provide experimental evidence for \(T_c\) enhancement in oxygen deficient films on highly reduced and conducting \(SrTiO_3\) substrates. \(T_c\) onset of 50-70 K was found in Meissner and transport measurements, which indicates superconductivity in islands or domains in our films, where \(T_c\) of zero resistance is obtained at 20-25 K. In addition, we observed a giant paramagnetic-Meissner effect peak at about 48 K, which further supports the existence of a superconductive transition just above it. Furthermore, an asymmetric or nonreciprocal and non-hysteretic superconductive diode effect was observed. The later could be fully polarized, and its polarity could be reversed. The specific phase responsible for these notable effects was not yet identified, and further research is needed in order to identify and isolate the relevant phase.
Superconductivity (cond-mat.supr-con), Materials Science (cond-mat.mtrl-sci)
Comments are welcomed. This file includes also a supplemental
Symplectic-Amoeba formulation of the non-Bloch band theory for one-dimensional two-band systems
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-02-26 20:00 EST
The non-Hermitian skin effect is a topological phenomenon, resulting in the condensation of bulk modes near the boundaries. Due to the localization of bulk modes at the edges, boundary effects remain significant even in the thermodynamic limit. This makes conventional Bloch band theory inapplicable and hinders the accurate computation of the spectrum. The Amoeba formulation addresses this problem by determining the potential from which the spectrum can be derived using the generalized Szegö's limit theorem, reducing the problem to an optimization of the Ronkin function. While this theory provides novel insights into non-Hermitian physics, challenges arise from the multiband nature and symmetry-protected degeneracies, even in one-dimensional cases. In this work, we investigate one-dimensional two-band class AII\(^\dagger\) systems, where Kramers pairs invalidate the conventional Amoeba formalism. We find that these challenges can be overcome by optimizing the band-resolved Ronkin functions, which is achieved by extrapolating the total Ronkin function. Finally, we propose a generalized Szegö's limit theorem for class AII\(^\dagger\) and numerically demonstrate that our approach correctly computes the potential and localization length.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
10 pages, 5 figures
High-throughput computational screening of Heusler compounds with phonon considerations for enhanced material discovery
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-26 20:00 EST
High-throughput (HTP) \(ab\) \(initio\) calculations are performed on 27,865 Heusler compositions, covering a broad range of regular, inverse, and half-Heusler compounds in both cubic and tetragonal phases. In addition to conventional stability metrics, such as formation energy, Hull distance, and magnetic critical temperature \(T_{\mathrm{c}}\), phonon stability is assessed by systematically conducting \(ab\) \(initio\) phonon calculations for over 8,000 compounds. The performance of \(ab\) \(initio\) stability criteria is systematically assessed against 189 experimentally synthesized compounds, and magnetic critical temperature calculations are validated using 59 experimental data points. As a result, we identify 631 stable compounds as promising candidates for further functional material exploration. Notably, 47 low-moment ferrimagnets are identified, with their spin polarization and anomalous Hall/Nernst conductivity calculated to provide insights into potential applications in spintronics and energy harvesting. Furthermore, our analyses reveal linear relationship between \(T_{\mathrm{c}}\) and magnetization in 14 systems and correlations between stability and atomic properties such as atomic radius and ionization energy. The regular/inverse structures preference in \(X_2YZ\) compound and tetragonal distortion are also investigated for a broad Heusler family.
Materials Science (cond-mat.mtrl-sci)
Stacking, Strain-Engineering Induced Altermagnetism, Multipiezo Effect, and Topological State in Two-Dimensional Materials
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-26 20:00 EST
Wei Xun, Xin Liu, Youdong Zhang, Yin-Zhong Wu, Ping Li
Altermagnetism, as a newly identified form of unconventional antiferromagnetism, enables the removal of spin degeneracy in the absence of net magnetization that provides a platform for the low power consumption and ultra-fast device applications. However, the rare attention has been paid to the relationship between stacking, strain and altermagnet, multipiezo effect and topological state. Here, we propose a mechanism to realize the altermagnet, multipiezo effect, and topological state in two-dimensional materials by the stacking and strain engineering. Based on the analysis of symmetry, we find that the spin splitting feature related to the Ut, PTt, MzUt, or MzPTt symmetries in altermagnet multilayers. In addition, we find that the stacking engineering can effectively realize the transform from antiferromagnetism to altermagnetism and semiconductor to metal for the Jauns bilayer V2SeTeO. More interestingly, the strain not only induces an intriguing multipiezo effect, encompassing the piezovalley, piezomagnetism and piezoelectric, but also achieves the abundant topological phase. Our findings offer a generalized direction for manipulating the spin splitting, valley polarization, and topological states, promoting practical application of valleytronic and spintronic devices based on two-dimensional altermagnets.
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
8 pages, 5 figures
A Peanut-hull-PLA based 3D printing filament with antimicrobial effect
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-02-26 20:00 EST
Sabarinathan Palaniyappan, Narain Kumar Sivakumar, Ahmed S. Dalaq
Peanut hulls, also known as Arachis hypogaea L. particles (AHL), are an abundant biomass source with a long shelf life. In this study, we incorporate peanut hull powder into PLA polymer, imparting recyclability, biodegradability, and biocompatibility, along with the antimicrobial properties of AHL particles. In particular, we treat AHL particles as a reinforcement for PLA polymer to produce 3D printing filament compatible with the fused filament fabrication (FFF) 3D printing method. We provide a step-by-step method for preparing AHL particles, incorporating them into PLA, and ultimately forming high-quality filaments. We assess the quality of the filaments in terms of extruded dimensions, mechanical strength, and elastic modulus, along with physical properties such as porosity and melt flow index. We evaluate the printability and wettability of the filaments as well. Notably, and unlike other biomass-based reinforcements in PLA, AHL preserves the filament's strength and enhances its elastic modulus. 3D-printed components fabricated using our PLA-AHL filaments successfully retain their antimicrobial properties and exhibit increased overall hardness. However, this comes at the expense of forming more microvoids and a rougher surface, making the material more prone to fracture and leading to a slight reduction in fracture toughness with increasing AHL mass fraction.
Soft Condensed Matter (cond-mat.soft), Applied Physics (physics.app-ph)
30 pages, 7 figures
Multimode operation of a superconducting nanowire switch in the nanosecond regime
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-02-26 20:00 EST
Zoltán Scherübl, Mátyás Kocsis, Tosson Elalaily, Lőrinc Kupás, Martin Berke, Gergő Fülöp, Thomas Kanne, Karl Berggren, Jesper Nygård, Szabolcs Csonka, Péter Makk
Superconducting circuits are promising candidates for future computational architectures, however, practical applications require fast operation. Here, we demonstrate fast, gate-based switching of an Al nanowire-based superconducting switch in time-domain experiments. We apply voltage pulses on the gate while monitoring the microwave transmission of the device. Utilizing the usual leakage-based operation these measurements yield a fast, 1--2~ns switching time to the normal state, possibly limited by the bandwidth of our setup, and a 10--20~ns delay in the normal to superconducting transition. However, having a significant capacitance between the gate and the device allows for a novel operation, where the displacement current, induced by the fast gate pulses, drives the transition. The switching from superconducting to the normal state yields a similar fast timescale, while in the opposite direction the switching is significantly faster (4--6~ns) than the leakage based operation, which may be further improved by better thermal design. The measured short timescales and novel switching operation open the way for future fast and low-power-consumption applications.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
10 pages, 6 figures
Photoexcitation-induced Stacking Transition Assisted by Intralayer Reconstruction in Charge-Density-Wave Materials
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-26 20:00 EST
Jin Zhang, Yang Yang, Jia Zhang, Mengxue Guan, Jiyu Xu, Kun Yang, Xinghua Shi, Sheng Meng
Laser excitation has emerged as an effective tool for probing microscopic interactions and manipulating phases of matter. Among charge density wave (CDW) materials, 1T-TaS2 has garnered significant attention due to its diverse stacking orders and photoexcited responses. However, the mechanisms driving transitions among different stacking orders and the microscopic out-of-equilibrium dynamics remain unclear. We elucidate that photoexcitation can introduce interlayer stacking order transitions facilitated by laser-induced intralayer reconstruction in 1T-TaS2. Importantly, our finding reveals a novel pathway to introduce different phases through laser excitations, apparently distinct from thermally-induced phase transitions via interlayer sliding. In particular, photoexcitation is able to considerably change potential energy surfaces and evoke collective lattice dynamics. Consequently, the laser-induced intralayer reconstruction plays a crucial role in interlayer stacking-order transition, offering a new method to create exotic stackings and quantum phases. The exploration opens up great opportunities for manipulating CDW phases and electronic properties on the femtosecond timescale.
Materials Science (cond-mat.mtrl-sci)
10 pages, 4 figures
Analysis methodology of coherent oscillations in time- and angle-resolved photoemission spectroscopy
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-26 20:00 EST
Nicolas Gauthier, Hadas Soifer, Jonathan A. Sobota, Heike Pfau, Edbert J. Sie, Aaron M. Lindenberg, Zhi-Xun Shen, Patrick S. Kirchmann
Oscillatory signals from coherently excited phonons are regularly observed in ultrafast pump-probe experiments on condensed matter samples. Electron-phonon coupling implies that coherent phonons also modulate the electronic band structure. These oscillations can be probed with energy and momentum resolution using time- and angle-resolved photoemission spectroscopy (trARPES) which reveals the orbital dependence of the electron-phonon coupling for a specific phonon mode. However, a comprehensive analysis remains challenging when multiple coherent phonon modes couple to multiple electronic bands. Complex spectral line shapes due to strong correlations in quantum materials add to this challenge. In this work, we examine how the frequency domain representation of trARPES data facilitates a quantitative analysis of coherent oscillations of the electronic bands. We investigate the frequency domain representation of the photoemission intensity and . Both quantities provide complimentary information and are able to distinguish oscillations of binding energy, linewidth and this http URL analyze a representative trARPES dataset of the transition metal dichalcogenide WTe\(_2\) and construct composite spectra which intuitively illustrate how much each electronic band is affected by a specific phonon mode. We also show how a linearly chirped probe pulse can generate extrinsic artifacts that are distinct from the intrinsic coherent phonon signal.
Materials Science (cond-mat.mtrl-sci)
Distributed Current Injection into a 1D Ballistic Edge Channel
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-02-26 20:00 EST
Kristof Moors, Christian Wagner, Helmut Soltner, Felix Lüpke, F. Stefan Tautz, Bert Voigtländer
Quantized charge transport through a 1D ballistic channel was famously explained decades ago by Rolf Landauer, by considering local injection of charge carriers from two contacts at the ends of the 1D channel. With the rise of quantum (spin/anomalous) Hall insulators, i.e., 2D material systems with ballistic 1D edge states along their perimeter, a different geometry has become relevant: The distributed injection of charge carriers from a 2D half-plane with residual conductivity into the 1D edge channel. Here, we generalize Landauer's treatment of ballistic transport to such a setup and identify hallmark signatures that distinguish a ballistic channel from a resistive one.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Main Text (6 pages, 3 figures) and Supplemental Material (15 pages, 4 figures)
Revisiting the spin-orbit scattering in small-sized superconducting particles in the magnetic field
New Submission | Superconductivity (cond-mat.supr-con) | 2025-02-26 20:00 EST
The Knight shift of nuclear magnetic resonance is an experimental probe of the paramagnetic spin susceptibility in metals. Information about the electron pairing in superconductors can be extracted from the Knight shift in the small-sized particles. The finite zero-temperature magnitude of paramagnetic susceptibility observed in the superconducting particles has been associated with the spin-orbit scattering of conduction electrons. The conventional treatment has delivered the paramagnetic susceptibility magnitude proportional to the square of the spin-orbit interaction amplitude. Here we examine the coupling between the superconducting current and the spin-orbit scattering of conduction electrons in the small-sized particles. Such interference coupling, absent in the normal state, results in an additional spin polarization of the conduction electrons generating the superconducting current in the magnetic field. This anomalous effect delivers the noticeably larger contribution to the paramagnetic susceptibility. The magnitude of the effect as well as the contribution to the paramagnetic susceptibility prove to be proportional to the amplitude of spin-orbit interaction. The frequency of electron paramagnetic resonance is shifted as well.
Superconductivity (cond-mat.supr-con), Other Condensed Matter (cond-mat.other)
6 pages, 3 figures
Higher-order contagion processes in 1.99 dimensions
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-02-26 20:00 EST
Sandro Melon, Andrea Gabrielli, Pablo Villegas
Higher-order interactions have recently emerged as a promising framework for describing new dynamical phenomena in heterogeneous contagion processes. However, a fundamental open question is how to understand their contribution in the eyes of the physics of critical phenomena. Based on mesoscopic field-theoretic Langevin descriptions, we show that: (i) pairwise mechanisms as facilitation or thresholding are formally equivalent to higher-order ones, (ii) pairwise interactions at coarse-grained scales govern the higher-order contact process and, (iii) classical Imry-Ma arguments hold for networks with low spectral dimension. In short, we demonstrate that classical field theories, grounded on model symmetries and/or network dimensionality, still capture the nature of the phase transition, also predicting finite-size effects in real and synthetic networks.
Statistical Mechanics (cond-mat.stat-mech), Disordered Systems and Neural Networks (cond-mat.dis-nn)
5 pages, 4 figures, and Supplemental Material
Surface acoustic wave driven acoustic spin splitter in d-wave altermagnetic thin films
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-02-26 20:00 EST
Pieter M. Gunnink, Jairo Sinova, Alexander Mook
The generation of spin currents is a key challenge in the field of spintronics. We propose using surface acoustic waves (SAWs) to generate spin currents in altermagnetic thin films, thereby realizing an acoustic spin splitter. Altermagnets, characterized by spin-polarized electrons and magnons, provide a versatile platform where SAWs can drive spin currents carried by both charge carriers and magnons. This acoustic spin splitter can be implemented in both metallic and insulating altermagnetic thin films, offering broad material applicability and a novel way to detect the spin splitter effect in insulating altermagnetic thin film. We examine a realistic experimental setup where a heavy metal layer, such as platinum, is used to convert the spin current into a measurable charge current via the inverse spin Hall effect. For representative material parameters, we calculate the expected spin current and the corresponding inverse spin Hall voltage. Furthermore, we demonstrate that tuning the SAW frequency allows for precise control over the spin current, highlighting the versatility and potential of the acoustic spin splitter for future spintronics applications.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
6 pages, 3 figures. Supplementary Material (SM) available under "Ancillary files". Data available at https://doi.org/10.5281/zenodo.14892781
Algebraic Exact Solution for Driven Landau Levels in Two-dimensional Electron Gases
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-02-26 20:00 EST
Li-kun Shi, Inti Sodemann Villadiego
Controlling quantum systems with time-dependent fields opens avenues for engineering novel states of matter and exploring non-equilibrium phenomena. Landau levels in two-dimensional electron gases (2DEGs), with their discrete energy spectrum and characteristic cyclotron dynamics, provide an important platform for realizing and studying such driven quantum systems. While exact solutions for driven Landau levels exist, they have been limited to specific gauges or representations. In this work, we present an algebraic, gauge- and representation-independent exact solution for driven Landau levels in 2DEGs subject to arbitrary time-dependent electromagnetic fields. Our approach, based on a time-dependent unitary transformation via the displacement operator, provides clear physical insights into the driven quantum dynamics. We apply this method to derive the exact Floquet states and quasienergies for periodically driven Landau levels, and we extend our analysis to the resonant driving regime, where the Floquet picture breaks down and the electron wavefunction exhibits unbounded spatial spreading. Furthermore, we calculate the instantaneous energy absorption rate, revealing distinct absorption behaviors between coherent states and Fock or thermal states, stemming from quantum interference effects.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Multifield Induced Antiferromagnet Transformation into Altermagnet and Realized Anomalous Valley Hall Effect in Two-dimensional Materials
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-26 20:00 EST
Hanbo Sun, Pengqiang Dong, Chao Wu, Ping Li
Altermagnetism, as a new category of collinear magnetism distinct from traditional ferromagnetism and antiferromagnetism, exhibits the spin splitting without net magnetization. Currently, researchers are focus on searching three-dimensional altermagnetism and exploring its novel physical properties. However, there is a lack of understanding of the physical origin of two-dimensional altermagnetic emergent behavior. Here, we propose an approach to realize the transition from Neel antiferromagnetism to altermagnetism in two-dimensional system using an electric field, Janus structure, and ferroelectric substrate. In monolayer VPSe3, we demonstrate that multiple-physical-fields cause the upper and lower Se atoms unequal to break PT symmetry, resulting in altermagnetic spin splitting. Noted that monolayer VPSe3 produces a spontaneous valley splitting of 2.91 meV at the conduction band minimum. The electric field can effectively tune the valley splitting magnitude, while the Janus structure not only changes the valley splitting magnitude, but also alters the direction. More interestingly, when the ferroelectric polarization of Al2S3 is upward, the direction of valley polarization is switched and the magnitude is almost unchanged. However, the valley splitting sigfinicantly increases under the downward. It is worth noting that the ferroelectric polarization can switch altermagnetic effect and realize anomalous valley Hall effect. Besides, we reveal the microscopic mechanism of valley splitting by an effective Hamiltonian. Our findings not only provide a method to designing altermagnet, but also enriches the valley physics.
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
8 pages, 5 figures
Continuously tunable anomalous Hall crystals in rhombohedral heptalayer graphene
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-02-26 20:00 EST
Hanxiao Xiang, Jing Ding, Jiannan Hua, Naitian Liu, Wenqiang Zhou, Qianmei Chen, Kenji Watanabe, Takashi Taniguchi, Na Xin, Wei Zhu, Shuigang Xu
The interplay of electronic interactions and nontrivial topology can give rise to a wealth of exotic quantum states. A notable example is the formation of Wigner crystals driven by strong electron-electron interactions. When these electronic crystals emerge in a parent band carrying a large Berry curvature, they can exhibit topologically nontrivial properties as anomalous Hall crystals, spontaneously breaking both continuous translational symmetry and time-reversal symmetry. Here, we report the experimental observation of tunable anomalous Hall crystals in rhombohedral heptalayer graphene moiré superlattices. At filling factors near one electron per moiré unit cell (v=1), we identify a series of incommensurate Chern insulators with a Chern number of C=1. Furthermore, we observe spontaneous time-reversal symmetry breaking spanning the entire filling range from v=1 to v=2, manifesting as anomalous Hall effects with pronounced magnetic hysteresis. Notably, anomalous Hall crystals with a high Chern number C=3 are observed over generic fillings ranging from v=1.5 to v=2. These anomalous Hall crystals are incommensurate with the moiré superlattice and exhibit dispersive fan diagrams consistent with the Streda formula, with their positions continuously tunable through displacement fields. Remarkably, these partially filled Chern insulators display Chern numbers distinct from their parent bands. Our findings demonstrate the rich variety of electronic crystalline states in rhombohedral graphene moiré superlattices, offering valuable insights into the strongly correlated topological phases.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci), Strongly Correlated Electrons (cond-mat.str-el)
4 figures
Listen! It's a phase transition. The sound of a shape-memory alloy
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-26 20:00 EST
Carlo Andrea Rozzi, Annamaria Lisotti, Guido Goldoni, Valentina De Renzi
The remarkable properties and numerous technological applications of shape-memory alloys are due to a solid-to-solid phase transition involving a temperature-driven rearrangement of their crystal structure. Here, we propose a simple, yet effective experiment probing the emitted by a Ni\(_{40}\)Ti\(_{50}\)Cu\(_{10}\) bar at different temperatures crossing the transition between martensite and austenite phases and we discuss the relationship with the elastic properties of the material. We show that the phase transition{, which occurs slightly above room temperature,} can be qualitatively monitored by the ear and that a quantitative description of the phenomenon can be obtained using a very simple setup and sound analysis tools. We argue that such a sound-based investigation provides an unusual, stimulating way to experimentally introduce solid-to-solid phase transitions suitable for undergraduate courses.
Materials Science (cond-mat.mtrl-sci), Physics Education (physics.ed-ph)
Novel Strontium Carbides Under Compression
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-26 20:00 EST
Nikita Rybin, Evgeny Moerman, Pranab Gain, Artem R. Oganov, Alexander Shapeev
Exploring the chemistry of materials at high pressures has lead to the discovery of previously unknown exotic compounds. Here, we systematically search for all thermodynamically stable Sr-C compounds under pressure (up to 100 GPa) using the ab initio evolutionary crystal structure prediction method. Our search lead to the discovery of hitherto unknown phases of SrC3, Sr2C5, Sr2C3, Sr2C, Sr3C2, and SrC. The newly discovered crystal structures feature a variety of different carbon environments ranging from isolated C anions and C-dimers to exotic polyatomic carbon anions including chains, stripes, and infinite ribbons consisting of pentagonal C5 and hexagonal C6 rings. Dynamical stability of all predicted compounds is confirmed by phonons calculations. Bader analysis unravels very diverse chemistry in these compounds and bonding patterns in some of them can be described using Zintl-Klemm rule.
Materials Science (cond-mat.mtrl-sci), Computational Physics (physics.comp-ph)
Magneto-Optics of Anisotropic Exciton Polaritons in Two-Dimensional Perovskites
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-02-26 20:00 EST
Jonas K. König, Jamie M. Fitzgerald, Ermin Malic
Layered 2D organic-inorganic perovskite semiconductors support strongly confined excitons that offer significant potential for ultrathin polaritonic devices due to their tunability and huge oscillator strength. The application of a magnetic field has proven to be an invaluable tool for investigating the exciton fine structure observed in these materials. Yet, the combination of an in-plane magnetic field and the strong coupling regime has remained largely unexplored. In this work, we combine microscopic theory with a rigorous solution of Maxwell's equations to model the magneto-optics of exciton polaritons in 2D perovskites. We predict that the brightened dark exciton state can enter the strong coupling regime. Furthermore, the magnetic-field-induced mixing of polarization selection rules and the breaking of in-plane symmetry lead to highly anisotropic polariton branches. This study contributes to a better understanding of the exciton fine structure in 2D perovskites and demonstrates the cavity control of highly anisotropic and polarization-sensitive exciton polaritons.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Main text: 23 pages, 4 figures Supplementary information: 14 pages, 7 figures
Electronic Structures across the Superconductor-Insulator Transition at La\(_{2.85}\)Pr\(_{0.15}\)Ni\(_2\)O\(_7\)/SrLaAlO\(_4\) Interfaces
New Submission | Superconductivity (cond-mat.supr-con) | 2025-02-26 20:00 EST
Heng Wang, Haoliang Huang, Guangdi Zhou, Wei Lv, Changming Yue, Lizhi Xu, Xianfeng Wu, Zihao Nie, Yaqi Chen, Yu-Jie Sun, Weiqiang Chen, Hongtao Yuan, Zhuoyu Chen, Qi-Kun Xue
Interfacial superconductivity discovered in bilayer nickelate heterostructures opens new avenues for effective tunability and control. Here, we report the superconductor-insulator transition in La\(_{2.85}\)Pr\(_{0.15}\)Ni\(_2\)O\(_7\)/SrLaAlO\(_4\) interfaces, with corresponding electronic structures revealed using synchrotron low-temperature X-ray absorption spectroscopy (XAS) and X-ray linear dichroism (XLD). In addition to the valence states of each element within the films determined by XAS, XLD at the O K edge pre-peak reveals hybridizations involving both 2p\(_{z}\) and 2p\(_{x}\)/2p\(_{y}\) orbitals, which are concomitantly suppressed upon oxygen loss. Intriguingly, such oxygen loss that eliminates superconductivity, induces a qualitative XLD change at the Ni L\(_{2}\) edge, implying significant transformations among 3d\(_{x^{2}}\) \(_{-y^{2}}\) and 3d\(_{z^{2}}\) energy bands near the Fermi level. Our findings establish an element- and orbital-resolved electronic framework for the origin of superconductivity.
Superconductivity (cond-mat.supr-con), Materials Science (cond-mat.mtrl-sci), Strongly Correlated Electrons (cond-mat.str-el)
under review
Orbital Fulde-Ferrell State versus Orbital Larkin-Ovchinnikov State
New Submission | Superconductivity (cond-mat.supr-con) | 2025-02-26 20:00 EST
Orbital Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) states are analyzed within mean-field theory, where orbital FF state is layer-polarized with inversion symmetry broken, while orbital LO state is Josephson vortex array with translation symmetry reduced. Phase diagrams of orbital FFLO states are obtained, and properties such as induced orders, superconducting diode effects, Fraunhofer pattern and topological defects are studied for the probe of FF versus LO states.
Superconductivity (cond-mat.supr-con)
4 pages (maintext)+1 page (references)+2 pages (appendix), 3 figures
Growth orientation and magnetic properties of GdVO\(_3\) tailored by epitaxial strain engineering
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-26 20:00 EST
M. Martirosyan, A. Gudima, J. Varignon, J. Ghanbaja, S. Migot, A. David, M. Guennou, O. Copie
Transition-metal oxides with an ABO\(_3\) perovskite structure exhibit significant coupling between spin, orbital, and lattice degrees of freedom, highlighting the crucial role of lattice distortion in tuning the electronic and magnetic properties of these systems. In this study, we grow a series of antiferromagnetic GdVO\(_3\) thin films on different substrates introducing various strain values. The results demonstrate that the strain not only affects the material's structure and magnetic transition temperature but also influences the growth direction of the orthorhombic unit cell. A correlation is observed between the orientation of the orthorhombic long axis direction and the material's Néel temperature. DFT calculations highlighting the link between strain, lattice distortions and magnetic characteristics confirm these conclusions. Our findings demonstrate that the development of novel features in RVO\(_3\) through material design requires control of growth orientation through strain engineering.
Materials Science (cond-mat.mtrl-sci)
Multicaloric effect in Fe48Rh52 alloy: case of combination magnetic field and uniaxial tension
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-26 20:00 EST
Abdulkarim Amirov, Dibir Yusupov, Alexey Komlev, Maksim Koliushenkov, Alexander Kamantsev, Akhmed Aliev
Mono and multicaloric effects in Fe48Rh52 alloy under applied magnetic field, uniaxial tension and their combination were studied by direct method. It was found that for single cases, the inverse caloric effect was observed with delta TAD = -2.9 K (1T) at 330 K in the case of the magnetocaloric effect and delta TAD = -0.5 K (104 MPa) at 328 K in the case of the elastocaloric effect. The combination co-application of the external 1 T magnetic field and a 104 MPa tensile results to the observation of a synergistic effect with delta TAD = -3.4 K at 330 K when a, which exceeds similar values for mono caloric effects. As was shown from comparison of calculation and experiments multicaloric effect it is not a sum of mono caloric effects and several factors as geometry of the sample as well the protocol for applying external fields should be taken into account. It was shown that the distribution of mechanical stresses in the Fe48Rh52 sample with a geometry in the shape of a plate with holes is heterogeneous, which should be taken into account when measuring calorific effects using tension through holes
Materials Science (cond-mat.mtrl-sci)
Scrutinizing the Mori memory function for diffusion in periodic quantum systems
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-02-26 20:00 EST
Scott D. Linz, Jiaozi Wang, Robin Steinigeweg, Jochen Gemmer
Diffusion is an ubiquitous phenomenon. It is a widespread belief that as long as the area under a current autocorrelation function converges in time, the corresponding spatiotemporal density dynamics should be diffusive. This may be viewed as a result of the combination of linear response theory with the Einstein relation. However, attempts to derive this statement from first principles are notoriously challenging. We first present a counterexample by constructing a correlation functions of some density wave, such that the area under the corresponding current autocorrelation function converges, but the dynamics do not obey a diffusion equation. Then we will introduce a method based on the recursion method and the Mori memory formalism, that may help to actually identify diffusion. For a decisive answer, one would have to know infinitely many so called Lanczos coefficients, which is unattainable in most cases. However, in the examples examined in this paper, we find that the practically computable number of Lanczos coefficients suffices for a strong guess.
Statistical Mechanics (cond-mat.stat-mech), Quantum Physics (quant-ph)
12 pages, 7 figures
Seeing the unseen: laser speckles as a tool for coagulation tracking
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-02-26 20:00 EST
Christoph Haessig, Flemming Møller
The ability to measure protein functionality is critical for the development of plant-based products, particularly with respect to gelation behavior, which is vital for food structure and texture. Small amplitude oscillatory shear tests remain the standard for monitoring protein gelation; however, these methods are costly, time-consuming, and require physical contact with the sample. Laser speckle rheology, an optical-based technique, offers a contactless alternative by assessing rheological properties through speckle pattern fluctuations. In this work, we present a simple laser speckle rheology setup, utilizing a diode laser and a digital camera, to monitor rheological changes during the rennet coagulation of milk. We use a viscoelasticity index, derived from a two-dimensional linear correlation, to quantify speckle pattern fluctuations. The laser speckle rheology method is compared with conventional small amplitude oscillatory shear rheology. Results demonstrate that key characteristics of the coagulation process, including coagulation and gelation times, are temporally aligned between the two methods. Furthermore, the viscoelasticity index allows for the comparison of the complex modulus in samples with similar compositions under consistent acquisition parameters. These findings underscore the potential of laser speckle rheology as a cost-effective, rapid, and contactless approach for capturing protein gelation, providing a viable alternative to conventional shear rheological methods.
Soft Condensed Matter (cond-mat.soft)
The supplementary video will be available with the final manuscript
Controlling dynamics of stochastic systems with deep reinforcement learning
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-02-26 20:00 EST
A properly designed controller can help improve the quality of experimental measurements or force a dynamical system to follow a completely new time-evolution path. Recent developments in deep reinforcement learning have made steep advances toward designing effective control schemes for fairly complex systems. However, a general simulation scheme that employs deep reinforcement learning for exerting control in stochastic systems is yet to be established. In this paper, we attempt to further bridge a gap between control theory and deep reinforcement learning by proposing a simulation algorithm that allows achieving control of the dynamics of stochastic systems through the use of trained artificial neural networks. Specifically, we use agent-based simulations where the neural network plays the role of the controller that drives local state-to-state transitions. We demonstrate the workflow and the effectiveness of the proposed control methods by considering the following two stochastic processes: particle coalescence on a lattice and a totally asymmetric exclusion process.
Statistical Mechanics (cond-mat.stat-mech), Machine Learning (cs.LG), Computational Physics (physics.comp-ph)
8 pages, 3 figures
Inverse Materials Design by Large Language Model-Assisted Generative Framework
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-26 20:00 EST
Yun Hao, Che Fan, Beilin Ye, Wenhao Lu, Zhen Lu, Peilin Zhao, Zhifeng Gao, Qingyao Wu, Yanhui Liu, Tongqi Wen
Deep generative models hold great promise for inverse materials design, yet their efficiency and accuracy remain constrained by data scarcity and model architecture. Here, we introduce AlloyGAN, a closed-loop framework that integrates Large Language Model (LLM)-assisted text mining with Conditional Generative Adversarial Networks (CGANs) to enhance data diversity and improve inverse design. Taking alloy discovery as a case study, AlloyGAN systematically refines material candidates through iterative screening and experimental validation. For metallic glasses, the framework predicts thermodynamic properties with discrepancies of less than 8% from experiments, demonstrating its robustness. By bridging generative AI with domain knowledge and validation workflows, AlloyGAN offers a scalable approach to accelerate the discovery of materials with tailored properties, paving the way for broader applications in materials science.
Materials Science (cond-mat.mtrl-sci), Machine Learning (cs.LG)
Luttinger compensated bipolarized magnetic semiconductor
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-26 20:00 EST
Peng-Jie Guo, Xiao-Yao Hou, Ze-Feng Gao, Huan-Cheng Yang, Wei Ji, Zhong-Yi Lu
Altermagnetic materials, with real-space antiferromagnetic arrangement and reciprocal-space anisotropic spin splitting, have attracted much attention. However, the spin splitting is small in most altermagnetic materials, which is a disadvantage to their application in electronic devices. In this study, based on symmetry analysis and the first-principles electronic structure calculations, we predict for the first time two Luttinger compensated bipolarized magnetic semiconductors Mn(CN)2 and Co(CN)2 with isotropic spin splitting as in the ferromagnetic materials. Our further analysis shows that the Luttinger compensated magnetism here depends not only on spin group symmetry, but also on the crystal field splitting and the number of d-orbital electrons. In addition, the polarized charge density indicates that both Mn(CN)2 and Co(CN)2 have the quasi-symmetry T{} , resulting from the crystal field splitting and the number of d-orbital electrons. The Luttinger compensated magnetism not only has the zero total magnetic moment as the antiferromagnetism, but also has the isotropic spin splitting as the ferromagnetism, thus our work not only provides theoretical guidance for searching Luttinger compensated magnetic materials with distinctive properties, but also provides a material basis for the application in spintronic devices.
Materials Science (cond-mat.mtrl-sci)
Magnetodielectric Properties in Two Dimensional Magnetic Insulators
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-26 20:00 EST
Koushik Dey, Hasina Khatun, Anudeepa Ghosh, Soumik Das, Bikash Das, Subhadeep Datta
Magnetodielectric (MD) materials are important for their ability to spin-charge conversion, magnetic field control of electric polarization and vice versa. Among these, two-dimensional (2D) van der Waals (vdW) magnetic materials are of particular interest due to the presence of magnetic anisotropy (MA) originating from the interaction between the magnetic moments and the crystal field. Also, these materials indicate a high degree of stability in the long-range spin order and may be described using suitable spin Hamiltonians of the Heisenberg, XY, or Ising type. Recent reports have suggested effective interactions between magnetization and electric polarization in 2D magnets. However, MD coupling studies on layered magnetic materials are still few. This review covers the fundamentals of magnetodielectric coupling by explaining related key terms. It includes the necessary conditions for having this coupling and sheds light on the possible physical mechanisms behind this coupling starting from phenomenological descriptions. Apart from that, this review classifies 2D magnetic materials into several categories for reaching out each and every class of materials. Additionally, this review summarizes recent advancements of some pioneer 2D magnetodielectric materials. Last but not the least, the current review provides possible research directions for enhancing magnetodielectric coupling in those and mentions the possibilities for future developments.
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
19 pages, 8 figures
Journal of Physics: Condensed Matter 2025
Functional interpolation expansion for nonequilibrium correlated impurities
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-02-26 20:00 EST
Daniel Werner, Enrico Arrigoni
We present a functional interpolation approach within the auxiliary master equation framework to efficiently and accurately solve correlated impurity problems in nonequilibrium dynamical mean-field theory (DMFT). By leveraging a near-exact auxiliary bath representation, the method estimates corrections via interpolation over a few bath realisations, significantly reducing computational cost and increasing accuracy. We illustrate the approach on the Anderson impurity model and on the Hubbard model within DMFT, capturing equilibrium and long-lived photodoped states.
Strongly Correlated Electrons (cond-mat.str-el)
Comments welcome!
Quantum entanglement of fermionic gapless symmetry protected topological phases in one dimension
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-02-26 20:00 EST
Wen-Hao Zhong, Hai-Qing Lin, Xue-Jia Yu
Quantum entanglement can be an effective diagnostic tool for probing topological phases protected by global symmetries. Recently, the notion of nontrivial topology in critical systems has been proposed and is attracting growing attention. In this work, as a concrete example, we explore the quantum entanglement properties of fermionic gapless topological states by constructing exactly solvable models based on stacked multiple Kitaev chains. We first analytically establish the global phase diagram using entanglement entropy and reveal three topologically distinct gapped phases with different winding numbers, along with three topologically distinct transition lines separating them. Importantly, we unambiguously demonstrate that two transition lines exhibit fundamentally different topological properties despite sharing the same central charge. Specifically, they display nontrivial topological degeneracy in the entanglement spectrum under periodic boundary conditions, thereby generalizing the Li-Haldane bulk-boundary correspondence to a broader class of fermionic gapless topological states. Additionally, we identify a novel Lifshitz multicritical point at the intersection of the three transition lines, which also exhibits nontrivial topological degeneracy. This work provides a valuable reference for investigating gapless topological phases of matter from the perspective of quantum entanglement.
Strongly Correlated Electrons (cond-mat.str-el), Statistical Mechanics (cond-mat.stat-mech), Quantum Physics (quant-ph)
12 pages, 8 figures. Any comments or suggestions are welcome!
Diverse dynamics in interacting vortices systems through tunable conservative and non-conservative coupling strengths
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-02-26 20:00 EST
A. Hamadeh, A. Koujok, D. R. Rodrigues, A. Riveros, V. Lomakin, G. Finocchio, G. De Loubens, O. Klein, P.Pirro
Magnetic vortices are highly tunable, nonlinear systems with ideal properties for being applied in spin wave emission, data storage, and neuromorphic computing. However, their technological application is impaired by a limited understanding of non conservative forces, that results in the open challenge of attaining precise control over vortex dynamics in coupled vortex systems. Here, we present an analytical model for the gyrotropic dynamics of coupled magnetic vortices within nano pillar structures, revealing how conservative and non conservative forces dictate their complex behavior. Validated by micromagnetic simulations, our model accurately predicts dynamic states, controllable through external current and magnetic field adjustments. The experimental verification in a fabricated nano pillar device aligns with our predictions, and it showcases the system's adaptability in dynamical coupling. The unique dynamical states, combined with the system's tunability and inherent memory, make it an exemplary foundation for reservoir computing. This positions our discovery at the forefront of utilizing magnetic vortex dynamics for innovative computing solutions, marking a leap towards efficient data processing technologies.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Coexisting Triferroic and Multiple Types of Valley Polarization by Structural Phase Transition in Two-Dimensional Materials
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-26 20:00 EST
Chao Wu, Hanbo Sun, Pengqiang Dong, Yin-Zhong Wu, Ping Li
The multiferroic materials, which coexist magnetism, ferroelectric, and ferrovalley, have broad practical application prospects in promoting the miniaturization and integration of spintronic and valleytronic devices. However, it is rare that there are triferroic orders and multiple types of valley polarization in a real material. Here, we propose a mechanism to realize triferroic order coexistence and multiple types of valley polarization by structural phase transition in two-dimensional (2D) materials. The 1T and 2H phase OsBr2 monolayers exhibit non-magnetic semiconductor and ferromagnetic semiconductor with valley polarization up to 175.49 meV, respectively. Interestingly, the 1T phase OsBr2 bilayer shows the tri-state valley polarization due to lattice symmetry breaking, while the valley polarization of 2H phase bilayer originates from the combined effect of time-reversal symmetry breaking and spin-orbit coupling. Furthermore, the valley polarization and ferroelectric polarization of 1T phase AB stackings and 2H phase AA stackings can be manipulated via interlayer sliding. Importantly, we have verified that the 2H phase can be transformed to 1T phase by Li+ ion intercalation, while the 2H phase can occur the structural phase transition into the 1T phase by infrared laser induction. Our work provides a feasible strategy for manipulating valley polarization and a design idea for nano-devices with nonvolatile multiferroic properties.
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
10 pages, 7 figures
Agnostic calculation of atomic free energies with the descriptor density of states
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-26 20:00 EST
Thomas D Swinburne, Clovis Lapointe, Mihai-Cosmin Marinica
We present a new method to evaluate vibrational free energies of atomic systems without a priori specification of an interatomic potential. Our model-agnostic approach leverages descriptors, high-dimensional feature vectors of atomic structure. The entropy of a high-dimensional density, the descriptor density of states, is accurately estimated with conditional score matching. Casting interatomic potentials into a form extensive in descriptor features, we show free energies emerge as the Legendre-Fenchel conjugate of the descriptor entropy, avoiding all high-dimensional integration. The score matching campaign requires less resources than fixed-model sampling and is highly parallel, reducing wall time to a few minutes, with tensor compression schemes allowing lightweight storage. Our model-agnostic estimator returns differentiable free energy predictions over a broad range of potential parameters in microseconds of CPU effort, allowing rapid forward and back propagation of potential variations through finite temperature simulations, long desired for uncertainty quantification and inverse design. We test predictions against thermodynamic integration calculations over a broad range of models for BCC, FCC and A15 phases of W, Mo and Fe at high homologous temperatures. Predictions pass the stringent accuracy threshold of 1-2 meV/atom (1/40-1/20 kcal/mol) for phase prediction with propagated score uncertainties robustly bounding errors. We also demonstrate targeted fine-tuning, reducing the alpha-gamma transition temperature in a non-magnetic machine learning model of Fe from 2030 K to 1063 K through back-propagation, with no additional sampling. Applications to liquids and fine-tuning foundational models are discussed along with the many problems in computational science which estimate high-dimensional integrals.
Materials Science (cond-mat.mtrl-sci), Statistical Mechanics (cond-mat.stat-mech)
Symmetry-driven Intrinsic Nonlinear Pure Spin Hall Effect
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-02-26 20:00 EST
Sayan Sarkar, Sunit Das, Amit Agarwal
The generation of pure spin current, spin angular momentum transport without charge flow, is crucial for developing energy-efficient spintronic devices with minimal Joule heating. Here, we introduce the intrinsic nonlinear pure spin Hall effect (NPSHE), where both linear and second-order charge Hall currents vanish. We show intrinsic second-order spin angular momentum transport in metals and insulators through a detailed analysis of the quantum geometric origin of different spin current contributions. Our comprehensive symmetry analysis identifies 39 magnetic point groups that support NPSHE, providing a foundation for material design and experimental realization. We predict significant nonlinear pure spin Hall currents in Kramers-Weyl metals even at room temperature, positioning them as potential candidates for NPSHE-based spin-torque devices. Our work lays a practical pathway for realizing charge-free angular momentum transport for the development of next-generation, energy-efficient spintronic devices.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
9 pages, 4 figures
Phonon thermal Hall as a lattice Aharonov-Bohm effect
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-02-26 20:00 EST
In a growing list of insulators, experiments find a misalignment between the heat flux and the thermal gradient vectors induced by magnetic field. This phenomenon, known as the phonon thermal Hall effect, implies energy flow without entropy production along the orientation perpendicular to the temperature gradient. Experiments find that the thermal Hall angle is maximal at the temperature at which the longitudinal thermal conductivity peaks. At this temperature, \(T_{max}\), Normal phonon-phonon collisions (which do not produce entropy) dominate Umklapp and boundary scattering events (which do). In the presence of a magnetic field, Born-Oppenheimer approximated molecular wave functions are known to acquire a geometric [Berry] phase. I will argue here that the survival of this phase in a crystal implies a complex amplitude for transverse phonons. This modifies three-phonon interference patterns, twisting the quasi-momentum of the outgoing phonon. The rough amplitude of the thermal Hall angle expected in this picture is set by the wavelength, \(\lambda_{max}\), and the crest displacement amplitude, \(u_m\), of transverse acoustic phonons at \(T_{max}\). Combined with the interatomic distance, \(a\) and the magnetic length, \(\ell_B\), it yields: \(\Theta_H \approx \lambda_{max}^2u_m^2a^{-2}\ell_B^{-2}\). This is surprisingly close to what has been experimentally found in black phosphorus, germanium and silicon.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci), Quantum Gases (cond-mat.quant-gas), Quantum Physics (quant-ph)
20 pages, 5 figures
Reaction-diffusion dynamics of the weakly dissipative Fermi gas
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-02-26 20:00 EST
Hannah Lehr, Igor Lesanovsky, Gabriele Perfetto
We study the one-dimensional Fermi gas subject to dissipative reactions. The dynamics is governed by the quantum master equation, where the Hamiltonian describes coherent motion of the particles, while dissipation accounts for irreversible reactions. For lattice one-dimensional fermionic systems, emergent critical behavior has been found in the dynamics in the reaction-limited regime of weak dissipation. Here, we address the question whether such features are present also in a gas in continuum space. We do this in the weakly dissipative regime by applying the time-dependent generalized Gibbs ensemble method. We show that for two body \(2A\to \emptyset\) and three \(3A\to \emptyset\) body annihilation, as well as for coagulation \(A+A\to A\), the density features an asymptotic algebraic decay in time akin to the lattice problem. In all the cases, we find that upon increasing the temperature of the initial state the density decay accelerates, but the asymptotic algebraic decay exponents are not affected. We eventually consider the competition between branching \(A\to A+A\) and the decay processes \(A\to \emptyset\) and \(2A\to \emptyset\). We find a second-order absorbing-state phase transition in the mean-field directed percolation universality class. This analysis shows that emergent behavior observed in lattice quantum reaction-diffusion systems is present also in continuum space, where it may be probed using ultra-cold atomic physics.
Statistical Mechanics (cond-mat.stat-mech), Quantum Gases (cond-mat.quant-gas)
36 pages, 11 figures
Z-basis measurements using mixed parity and direct readout
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-02-26 20:00 EST
Pieter Thijs Eendebak, Önder Gül
Many architectures for quantum information processing rely on qubits dedicated for the readout of a larger quantum register. These ancilla readout qubits present a physical overhead not contributing to the computational resource. A common implementation in spin qubit architectures is the readout schemes based on Pauli exclusion of charges confined in a double quantum dot, with one dot serving as the ancilla qubit. Here, using a three-qubit spin register and a Pauli exclusion-based readout, we present z-basis measurements of the entire register constructed with tomography, eliminating the physical overhead. We validate our approach with simulations which provide insight into potential sources of errors in the reconstruction. We also demonstrate our reconstruction by performing quantum state tomography on a GHZ state of a spin-qubit based device.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Quantum Physics (quant-ph)
Reversible magneto ionics in crystallized W Co20Fe60B20 MgO HfO2 ultra-thin films with perpendicular magnetic anisotropy
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-26 20:00 EST
Song Chen, Elmer Monteblanco, Benjamin Borie, Rohit Pachat, Shimpei Ono, Liza Herrera Diez, Dafiné Ravelosona
We have investigated electric field (E-field) induced modulation of perpendicular magnetic anisotropy (PMA) in both amorphous and crystalline W/CoFeB/MgO/HfO2 ultra-thin films. We find that in the amorphous state, the E-field effect is volatile and reversible, which is consistent with the conventional electrostatic effect through charge accumulation and depletion. In the crystallized system annealed at 370°C, we find that two effects are at play, a non-volatile and reversible voltage-induced effect on PMA and an electrostatic response. We discuss these results in terms of higher oxygen mobility at the crystallized CoFeB-MgO interface, which induces a non-volatile magneto-ionic response. Modulating PMA in crystallized CoFeB-MgO materials through ionic migration opens the path to integrating magneto-ionics in full magnetic tunnel junctions.
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Applied Physics (physics.app-ph)
Electrically Tunable Magnonic Bound States in the Continuum
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-02-26 20:00 EST
Xi-guang Wang, Guang-hua Guo, Jamal Berakdar, Hui Jing
Low energy excitations of a magnetically ordered system are spin waves with magnon being their excitation quanta. Magnons are demonstrated to be useful for data processing and communication. To achieve magnon transport across extended distances, it is essential to minimize magnonic dissipation which can be accomplished by material engineering to reduce intrinsic damping or by spin torques that can counteract damping. This study introduces an alternative methodology to effectively reduce magnon dissipation based on magnonic bound states in the continuum (BIC). We demonstrate the approach for two antiferromagnetically coupled magnonic waveguides, with one waveguide being attached to a current carrying metallic layer. The current acts on the attached waveguide with a spin-orbit torque effectively amplifying the magnonic signal. The setup maps on a non-Hermitian system with coupled loss and more loss, enabling the formation of dissipationless magnon BIC. We investigate the necessary criteria for the formation of magnon BIC through electric currents. The influences of interlayer coupling constant, anisotropy constants and applied magnetic field on the current-induced magnon BIC are analyzed. The identified effect can be integrated in the design of magnon delay lines, offering opportunities for the enhancement of magnonic devices and circuits.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Strongly Correlated Electrons (cond-mat.str-el)
15 pages, 4 figures
Halbach 2.0 -- Creating homogeneous fields with finite size magnets
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-26 20:00 EST
Homogeneous magnetic fields can be generated through the strategic arrangement of permanent magnets. The Halbach array serves as a prominent example of an effective design following this principle. However, it is a two-dimensional approach because it is optimal when placing infinitely long magnets -- line dipoles -- on a circle. If shorter, more realistic magnets are to be used, the optimal arrangement of magnetic moments diverges from the classical Halbach geometry. This paper presents optimal solutions for three-dimensional arrangements calculated for point dipoles, including optimized orientations for single rings and stacks of two rings. They are superior to the original Halbach arrangement and a modification described in the literature, both in terms of the strength and the homogeneity of the magnetic field. Analytic formulae are provided for both cases and tested by experimental realizations.
Materials Science (cond-mat.mtrl-sci), Instrumentation and Detectors (physics.ins-det)
18 pages, 22 figures
Table-top three-dimensional photoemission orbital tomography with a femtosecond extreme ultraviolet light source
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-26 20:00 EST
Wiebke Bennecke (1), Thi Lan Dinh (2), Jan Phillip Bange (1), David Schmitt (1), Marco Merboldt (1), Lennart Weinhagen (1), Bent van Wingerden (1), Fabio Frassetto (3), Luca Poletto (3), Marcel Reutzel (1), Daniel Steil (1), D. Russell Luke (2), Stefan Mathias (1,4), G. S. Matthijs Jansen (1) ((1) 1st Institute of Physics, University of Göttingen, Göttingen, Germany, (2) Institute for Numerical and Applied Mathematics, University of Göttingen, Göttingen, Germany, (3) Institute for Photonics and Nanotechnologies CNR-IFN, Padova, Italy, (4) International Center for Advanced Studies of Energy Conversion (ICASEC), University of Göttingen, Göttingen, Germany)
Following electronic processes in molecules and materials at the level of the quantum mechanical electron wavefunction with angstrom-level spatial resolution and with full access to its femtosecond temporal dynamics is at the heart of ultrafast condensed matter physics. A breakthrough invention allowing experimental access to electron wavefunctions was the reconstruction of molecular orbitals from angle-resolved photoelectron spectroscopy data in 2009, termed photoemission orbital tomography (POT). This invention puts ultrafast three-dimensional (3D) POT in reach, with many new prospects for the study of ultrafast light-matter interaction, femtochemistry and photo-induced phase transitions. Here, we develop a synergistic experimental-algorithmic approach to realize the first 3D-POT experiment using a short-pulse extreme ultraviolet light source. We combine a new variant of photoelectron spectroscopy, namely ultrafast momentum microscopy, with a table-top spectrally-tunable high-harmonic generation light source and a tailored algorithm for efficient 3D reconstruction from sparse, undersampled data. This combination dramatically speeds up the experimental data acquisition, while at the same time reducing the sampling requirements to achieve complete 3D information. We demonstrate the power of this approach by full 3D imaging of the frontier orbitals of a prototypical organic semiconductor absorbed on pristine Ag(110).
Materials Science (cond-mat.mtrl-sci), Instrumentation and Detectors (physics.ins-det)
The Maximum \(T_c\) of Conventional Superconductors at Ambient Pressure
New Submission | Superconductivity (cond-mat.supr-con) | 2025-02-26 20:00 EST
Kun Gao, Tiago F. T. Cerqueira, Antonio Sanna, Yue-Wen Fang, Đorđe Dangić, Ion Errea, Hai-Chen Wang, Silvana Botti, Miguel A. L. Marques
The theoretical maximum critical temperature (\(T_c\)) for conventional superconductors at ambient pressure remains a fundamental question in condensed matter physics. Through analysis of electron-phonon calculations for over 20,000 metals, we critically examine this question. We find that while hydride metals can exhibit maximum phonon frequencies of more than 5000 K, the crucial logarithmic average frequency \(\omega_\text{log}\) rarely exceeds 1800 K. Our data reveals an inherent trade-off between \(\omega_\text{log}\) and the electron-phonon coupling constant \(\lambda\), suggesting that the optimal Eliashberg function that maximizes \(T_c\) is unphysical. Based on our calculations, we identify Li\(_2\)AgH\(_6\) and its sibling Li\(_2\)AuH\(_6\) as theoretical materials that likely approach the practical limit for conventional superconductivity at ambient pressure. Analysis of thermodynamic stability indicates that compounds with higher predicted \(T_c\) values are increasingly unstable, making their synthesis challenging. While fundamental physical laws do not strictly limit \(T_c\) to low-temperatures, our analysis suggests that achieving room-temperature conventional superconductivity at ambient pressure is extremely unlikely.
Superconductivity (cond-mat.supr-con)
Imaging thick objects with deep-sub-angstrom resolution and deep-sub-picometer precision
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-26 20:00 EST
Wenfeng Yang, Haozhi Sha, Jizhe Cui, Rong Yu
Size effects are ubiquitous in the structural, mechanical, and physical properties of materials, making it highly desirable to study the intrinsic properties of thick objects through high-resolution structural analysis in transmission electron microscopy. Although deep-sub-angstrom resolution has been achieved with multislice electron ptychography, the sample thickness is typically very limited. By combining energy filtering and extended local-orbital ptychography (eLOP) that retrieves varying aberrations during electron scanning, here we report ptychographic reconstructions for silicon as thick as 85 nm, approximately three times larger than usual thickness threshold for conventional multislice electron ptychography. The elimination of aberration variations contributes to accurate reconstructions with an information limit of 18 pm and atomic position precision of 0.39 pm. Accurate ptychographic reconstructions for thick objects can facilitate the discovery or interpretation of intrinsic structural and physical phenomena in solids, which is of great significance in physics, chemistry, materials science, and semiconductor device engineering.
Materials Science (cond-mat.mtrl-sci)
Density functional theory of resonant inelastic x-ray scattering in the quasi-one-dimensional dimer iridate Ba3InIr2O9
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-02-26 20:00 EST
D.A. Kukusta, L.V. Bekenov, V.N. Antonov
We have investigated the electronic structure of Ba3InIr2O9 within the density-functional theory (DFT) using the generalized gradient approximation while considering strong Coulomb correlations (GGA+\(U\)) in the framework of the fully relativistic spin-polarized Dirac linear muffin-tin orbital band-structure method. We have investigated resonant inelastic x-ray scattering (RIXS) spectra at the Ir L3 K edge. The calculated results are in good agreement with experimental data. The RIXS spectrum of Ba3InIr2O9 at the Ir L3 edge possesses several sharp features below 2 eV corresponding to transitions within the Ir tg levels. The excitation located from 2 to 5 eV is due to tg -> eg transitions. The third wide structure situated at 5-12 eV appears due to charge transfer transitions. We have also presented comprehensive theoretical calculations of the RIXS spectrum at the oxygen K edge.
Strongly Correlated Electrons (cond-mat.str-el)
A novel spectroscopic probe of ultrafast magnetization dynamics in the extreme ultraviolet spectral range
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-26 20:00 EST
Johanna Richter, Somnath Jana, Robert Behrends, Carl S. Davies, Martin Hennecke, Daniel Schick, Clemens von Korff Schmising, Stefan Eisebitt
The development of spectroscopic techniques in the extreme ultraviolet (XUV) spectral range has significantly advanced the understanding of ultrafast interactions in magnetic systems triggered by optical excitation. In this work, we introduce a previously missing geometry that facilitates the observation of the ultrafast magnetization dynamics of magnetic systems with an out-of-plane magnetization grown on XUV opaque substrates. This novel approach to probe ultrafast magnetization dynamics combines the magneto-optical Kerr effect with the strong dependence of a sample's reflectance near its Brewster angle. It therefore works with linearly polarized light and does not require any additional polarizing optics. We provide a comprehensive analysis of the technique by presenting both simulations and experimental data as a function of the energy and the polarization of the XUV probe radiation as well as of the delay time after optical excitation.
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Optics (physics.optics)
10 pages, 6 figures
In situ growth and magnetic characterization of Cr Chloride monolayers
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-26 20:00 EST
Giuseppe Buccoliero, Pamella Vasconcelos Borges Pinho, Marli Dos Reis Cantarino, Francesco Rosa, Nicholas B. Brookes, Roberto Sant
Monolayer Chromium Dihalides and Trihalides materials can be grown on a variety of substrates by molecular beam epitaxy (MBE) regardless of the lattice mismatch, thanks to the van der Waals epitaxy. In this work, we studied the magnetic nature of Cr Chloride monolayers grown on Au(111), Ni(111) and graphene passivated-Ni(111) from the evaporation in ultra-high vacuum of the same halide precursor. Structural, morphological and chemical characterization were conducted in situ by low energy electron diffraction, scanning tunneling microscopy and Xray magnetic circular dichroism (XMCD). Owing to opposite chemical behaviour, Au(111) and Ni(111) promote the formation of two different valence compounds, i.e. CrCl\(_3\) and CrCl\(_2\), showing distinct magnetic properties at 4 K. When graphene is used to passivate the Ni(111) surface, the formation of CrCl\(_3\) becomes allowed on this substrate. The coexistence of CrCl\(_3\) and CrCl\(_2\), both showing few nm lateral size and super-paramagnetic features, is demonstrated by XMCD spectra displaying two dichroic peaks at the characteristic Cr\(^{3+}\) and Cr\(^{2+}\) energies. Site selective magnetization measurements performed with the photon energy tuned on the two absorption edges show reversed magnetization of some of the CrCl\(_2\) islands with respect to the CrCl\(_3\) domains, which is interpreted in terms of magnetic frustration.
Materials Science (cond-mat.mtrl-sci)
Lattice Parameters and Bulk Modulus of SrTi\(_{1-\mathit{x}}\)Mn\(_{\mathit{x}}\)O\(_{3}\) Perovskites: A Comparison of Exchange-Correlation Functionals with Experimental Validation
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-26 20:00 EST
Miroslav Lebeda, Jan Drahokoupil, Stanislav Kamba, Šimon Svoboda, Vojtěch Smola, Bogdan Dabrowski, Petr Vlčák
We assessed four exchange-correlation functionals (LDA CA-PZ, GGA parametrized by PBE, PBEsol, and WC) in predicting the lattice parameters of SrTi\(_{1-\mathit{x}}\)Mn\(_{\mathit{x}}\)O\(_{3}\) perovskites, assuming cubic structures. Predictions were verified using X-ray diffraction (XRD) for Mn content of \(\mathit{x}\) = 0.0, 0.1, 0.2, 0.3, 0.5, 1.0, confirming cubic symmetry and a linear decrease in lattice parameters with increasing Mn. PBEsol and WC demonstrated the highest precision (deviations < 0.20%). Additionally, bulk moduli were calculated using the same functionals and verified with the experimental bulk modulus of SrTiO\(_{3}\) (183 \(\pm\) 2 GPa, Pulse-Echo method). The predicted bulk moduli exhibited a slow, linear increase with increasing Mn. The best correspondence with the experimental bulk modulus was achieved by PBEsol and WC (deviations < 0.7%). These findings highlight the reliability of PBEsol and WC functionals for accurately modeling structural properties of SrTi\(_{1-\mathit{x}}\)Mn\(_{\mathit{x}}\)O\(_{3}\) perovskites, having better precision than commonly employed LDA and PBE functionals.
Materials Science (cond-mat.mtrl-sci)
14 pages, 6 figures, CC BY-NC-ND license
Nanoscale characterization of atomic positions in orthorhombic perovskite thin films
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-26 20:00 EST
M. Martirosyan, S. Passuti, G. Masset, J. Varignon, H. Chintakindi, J. Ghanbaja, S. Migot, A. Benedit-Cardenas, L. Pasquier, K. Dumesnil, L. Palatinus, W. Prellier, A. David, Ph. Boullay, O. Copie
The crystal structure determines many of the physical properties of oxide perovskites (ABO\(_3\)) and only a tiny modification of the lattice structure causes major changes in the functional properties through the interplay among spin, orbital and charge orders. The determination of characteristic distortions and symmetries is a valuable asset for understanding the structure-properties relationship and guiding the design of epitaxial oxide heterostructures, where electron degrees of freedom and correlated electronic states can be tailored. Even until new phases, otherwise absent in bulk materials, may appear. Here, we report on the in-depth structural characterization of 50~nm-LaVO\(_3\) thin film grown onto (110)-oriented DyScO\(_3\) by molecular beam epitaxy. We have investigated the heterostructure by means of x-ray diffraction, high-resolution and scanning transmission electron microscopies, scanning precession electron diffraction tomography and first-principle calculations. LaVO\(_3\) crystallizes in the orthorhombic \(Pbnm\) space group and is constrained by the substrate, which imposes a growth along the \([110]\) orthorhombic direction, over the 140 deposited unit cells. The mapping of the reciprocal space allows determining the orientation of the film and refining the lattice parameters. Using scanning transmission electron microscopy, we analyzed the structure of LaVO\(_3\), focusing on the determination of the antipolar displacement of the rare earth. Additionally, 3D electron diffraction enabled to resolve the atomic positions of all species within the film.
Materials Science (cond-mat.mtrl-sci)
Interplay of superconducting, metallic, and crystalline states of composite fermions at \(ν{=}1/6\) in wide quantum wells
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-02-26 20:00 EST
Ajit C. Balram, Anirban Sharma, J. K. Jain
Evidence for developing fractional quantum Hall effect (FQHE) at filling fraction \(\nu{=}1/6\) and \(1/8\) has recently been reported in wide GaAs quantum wells [Wang , PRL {}, 046502 (2025)]. In this article, we theoretically investigate the nature of the state at \(\nu{=}1/6\) as a function of the quantum well width and the density by considering composite-fermion (CF) crystals, CF Fermi sea, and various kinds of paired CF states. The \(f\)-wave paired state has the lowest energy among the paired CF states. However, for parameters of interest, the energies of the CF crystal, the CF Fermi liquid, and the \(f\)-wave paired CF state are too close to call. We, therefore, predict that {} the FQHE at \(\nu{=}1/6\) is experimentally confirmed, this state would be an \(f\)-wave paired state of CFs, which can be verified by measurement of its thermal Hall conductance. Exact diagonalization studies for systems with up to 8 electrons show that the ground states at \(\nu{=}n/(6n{\pm} 1)\) are incompressible for all widths and densities we have considered and well described by the corresponding Laughlin and Jain states. We propose a phase diagram for large quantum well widths and densities in which at zero disorder, incompressible FQHE states are stabilized at \(\nu{=}n/(6n{\pm} 1)\) and \(\nu{=}1/6\), but in between these fillings the CF crystal is stabilized. With disorder, which creates a spatial variation in the filling factor, two regimes are identified: (i) for small disorder, when the incompressible states percolate at the special fillings, FQHE with quantized Hall plateaus and vanishing longitudinal resistance should occur; and (ii) for larger disorder, when the CF crystal percolates, the longitudinal resistance rises with decreasing temperature but the domains of FQHE liquid produce minima at the special filling factors. The experiments are consistent with the latter scenario.
Strongly Correlated Electrons (cond-mat.str-el), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
13 pages, 7 figures
Mastering the growth of antimonene on Bi2Se3: strategies and insights
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-26 20:00 EST
Roberto Flammini, Conor Hogan, Stefano Colonna, Fabio Ronci, Mauro Satta, Marco Papagno, Ziya S. Aliev, Sergey V. Eremeev, Evgueni V. Chulkov, Zipporah R. Benher, Sandra Gardonio, Luca Petaccia, Giovanni Di Santo, Carlo Carbone, Paolo Moras, Polina M. Sheverdyaeva
Antimonene, the two-dimensional phase of antimony, appears in two distinct allotropes when epitaxially grown on Bi2Se3: the puckered asymmetric washboard ({}) and buckled honeycomb ({}) bilayer structures. As-deposited antimony films exhibit varying proportions of single {} and {} structures. We identify the conditions necessary for ordered, pure-phase growth of single to triple {}-antimonene bilayers. Additionally, we determine their electronic structure, work function, and characteristic core-level binding energies, offering an explanation for the relatively large chemical shifts observed among the different phases. This study not only establishes a protocol for achieving a single {} phase of antimonene but also provides key signatures for distinguishing between the different allotropes using standard spectroscopic and microscopic techniques.
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
9 pages, 4 figures, 77 references
New insights into the distribution of the topmost gap in random walks and Lévy flights
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-02-26 20:00 EST
Claude Godrèche, Jean-Marc Luck
Building upon the knowledge of the distribution of the first positive position reached by a random walker starting from the origin, one can derive new results on the statistics of the gap between the largest and second-largest positions of the walk, and recover known ones in a more direct manner.
Statistical Mechanics (cond-mat.stat-mech)
20 pages, 4 figures
Controllable Interlocking from Irregularity in Two-Phase Composites
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-02-26 20:00 EST
Chelsea Fox, Kyrillos Bastawros, Tommaso Magrini, Chiara Daraio
Natural materials often feature a combination of soft and stiff phases, arranged to achieve excellent mechanical properties, such as high strength and toughness. Many natural materials have even independently evolved to have similar structures to obtain these properties. For example, interlocking structures are observed in many strong and tough natural materials, across a wide range of length scales. Inspired by these materials, we present a class of two-phase composites with controllable interlocking. The composites feature tessellations of stiff particles connected by a soft matrix and we control the degree of interlocking through irregularity of particle size, geometry and arrangement. We generate the composites through stochastic network growth, using an algorithm which connects a hexagonal grid of nodes according to a coordination number, defined as the average number of connections per node. The generated network forms the soft matrix phase of the composites, while the areas enclosed by the network form the stiff reinforcing particles. At low coordination, composites feature highly polydisperse particles with irregular geometries, which are arranged non-periodically. In response to loading, these particles interlock with each other and primarily rotate and deform to accommodate non-uniform kinematic constraints from adjacent particles. In contrast, higher coordination composites feature more monodisperse particles with uniform geometries, which collectively slide. We then show how to control the degree of interlocking as a function of coordination number alone, demonstrating how irregularity facilitates controllability.
Soft Condensed Matter (cond-mat.soft), Materials Science (cond-mat.mtrl-sci)
Manuscript (~4000 words, excluding references), 5 figures, comprising 60 panels in total, and Supplementary Materials
From Champagne to Confined Polymer:Natural and Artifical Bubble Nucleation
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-02-26 20:00 EST
Carlos Arauz-Moreno, Keyvan Piroird, Elise Lorenceau
In this study, we present a novel experimental work on bubble nucleation and growth using a model system comprised by viscoelastic polyvinyl butyral (PVB) confined in a Hele-Shaw cell geometry that is decompressed at elevated temperatures. The driver is connected to the temperature-induced shift in chemical equilibrium experienced simultaneously by two gases present in the bulk. The latter becomes at the same time oversaturated with water vapor and slightly undersaturated in air. Our bubbles grow with various shapes and sizes depending on the initial morphology of the nucleus or the presence of neighboring bubbles. The likelihood of nucleation is related to the amount of water dissolved in the bulk and the imposed temperature. Counter-intuitively, the number of nuclei whence a bubble can grow is inversely correlated with said temperature. In an analogy with Champagne, we show that nucleation can either be natural, at trapped fibers or dust particles, or artificial, at crenels we purposefully made in the glass surface. Our results indicate that the growth rate of bubbles can be impacted by the nucleation mechanism.
Soft Condensed Matter (cond-mat.soft)
Single file dynamics of tethered random walkers
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-02-26 20:00 EST
S.B. Yuste, A. Baumgaertner, E. Abad
We consider the single-file dynamics of \(N\) identical random walkers moving with diffusivity \(D\) in one dimension (walkers bounce off each other when attempting to overtake). Additionally, we require that the separation between neighboring walkers cannot exceed a threshold value \(\Delta\) and therefore call them ``tethered walkers'' (they behave as if bounded by strings which tighten fully when reaching the maximum length \(\Delta\)). For finite \(\Delta\), we study the diffusional relaxation to the equilibrium state and characterize the latter [the long-time relaxation is exponential with a characteristic time that scales as \((N\Delta)^2/D\)]. In particular, our approximate approach for the \(N\)-particle probability distribution yields the one-particle distribution function of the central and edge particles [the first two positional moments are given as power expansions in \(\Delta/\sqrt{4Dt}\)]. For \(N=2\), we find an exact solution (both in the continuum case and on-lattice) and use it to test our approximations for one-particle distributions, positional moments, and correlations. For finite \(\Delta\) and arbitrary \(N\), edge particles move with an effective long-time diffusivity \(D/N\), in sharp contrast with the \(1/\ln(N)\)-behavior observed when \(\Delta=\infty\). Finally, we compute the probability distribution of the equilibrium system length and the associated entropy. We find that the force required to change this length by a given amount is linear in this quantity, the (entropic) spring constant being \(6k_BT/(N\Delta^2)\). In this respect, the system behaves like an ideal polymer. Our main analytical results are confirmed by Monte Carlo simulations.
Statistical Mechanics (cond-mat.stat-mech)
52 pages, 14 figures
Broadband surface phonon spectroscopy by time-domain extreme ultraviolet diffuse scattering
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-26 20:00 EST
F. Capotondi, A. Maznev, F. Bencivenga, S. Bonetti, D. Fainozzi, D. Fausti, L. Foglia, C. Gutt, N. Jaouen, D. Ksenzov, C. Masciovecchio, K. A. Nelson, I. Nikolov, M. Pancaldi, E. Pedersoli, B. Pfau, L. Raimondi, F. Romanelli, R. Totani, M. Trigo
We present experimental evidence that the dynamics of surface acoustic waves, with wavelengths ranging from tens to hundreds of nanometers, are encoded in the time-dependent diffuse scattering of extreme ultraviolet light. By measuring the diffuse scattering from a surface after an ultrafast optical excitation, we determined the dispersion relation of surface acoustic wave-packets across a broad range of wavevectors in various samples. The comparison of the signal amplitudes from samples with different surface morphologies suggests that the underlying excitation mechanism is related to the natural roughness of the samples surface. This simple and contactless approach represents a complementary experimental tool to transient grating or Brillouin spectroscopy, providing valuable insights into nanoscale surface dynamics.
Materials Science (cond-mat.mtrl-sci), Optics (physics.optics)
Main text + supplementary material