CMP Journal 2025-05-07
Statistics
Nature: 21
Nature Reviews Materials: 1
Physical Review Letters: 20
Physical Review X: 2
arXiv: 57
Nature
Global emergence of unprecedented lifetime exposure to climate extremes
Original Paper | Climate-change impacts | 2025-05-06 20:00 EDT
Luke Grant, Inne Vanderkelen, Lukas Gudmundsson, Erich Fischer, Sonia I. Seneviratne, Wim Thiery
Climate extremes are escalating under anthropogenic climate change1. Yet, how this translates into unprecedented cumulative extreme event exposure in a person’s lifetime remains unclear. Here we use climate models, impact models and demographic data to project the number of people experiencing cumulative lifetime exposure to climate extremes above the 99.99th percentile of exposure expected in a pre-industrial climate. We project that the birth cohort fraction facing this unprecedented lifetime exposure to heatwaves, crop failures, river floods, droughts, wildfires and tropical cyclones will at least double from 1960 to 2020 under current mitigation policies aligned with a global warming pathway reaching 2.7 °C above pre-industrial temperatures by 2100. Under a 1.5 °C pathway, 52% of people born in 2020 will experience unprecedented lifetime exposure to heatwaves. If global warming reaches 3.5 °C by 2100, this fraction rises to 92% for heatwaves, 29% for crop failures and 14% for river floods. The chance of facing unprecedented lifetime exposure to heatwaves is substantially larger among population groups characterized by high socioeconomic vulnerabilities. Our results call for deep and sustained greenhouse gas emissions reductions to lower the burden of climate change on current young generations.
Climate-change impacts, Projection and prediction
Twist-programmable superconductivity in spin-orbit-coupled bilayer graphene
Original Paper | Electronic properties and materials | 2025-05-06 20:00 EDT
Yiran Zhang, Gal Shavit, Huiyang Ma, Youngjoon Han, Chi Wang Siu, Ankan Mukherjee, Kenji Watanabe, Takashi Taniguchi, David Hsieh, Cyprian Lewandowski, Felix von Oppen, Yuval Oreg, Stevan Nadj-Perge
The relative twist angle between layers of near-lattice-matched van der Waals materials is critical for the emergent phenomena associated with moiré flat bands1,2,3. However, the concept of angle rotation control is not exclusive to moiré superlattices in which electrons directly experience a twist-angle-dependent periodic potential. Instead, it can also be used to induce programmable symmetry-breaking perturbations with the goal of stabilizing desired correlated states. Here we experimentally demonstrate ‘moiréless’ twist-tuning of superconductivity together with other correlated orders in Bernal bilayer graphene proximitized by tungsten diselenide. The precise alignment between the two materials systematically controls the strength of induced Ising spin-orbit coupling (SOC), profoundly altering the phase diagram. As Ising SOC is increased, superconductivity onsets at a higher displacement field and features a higher critical temperature, reaching up to 0.5 K. Within the main superconducting dome and in the strong Ising SOC limit, we find an unusual phase transition characterized by a nematic redistribution of holes among trigonally warped Fermi pockets and enhanced resilience to in-plane magnetic fields. The superconducting behaviour is theoretically compatible with the prominent role of interband interactions between symmetry-breaking Fermi pockets. Moreover, we identify two additional superconducting regions, one of which descends from an inter-valley coherent normal state and shows a Pauli-limit violation ratio exceeding 40, among the highest for all known superconductors4,5,6,7. Our results provide insights into ultraclean graphene superconductors and underscore the potential of utilizing moiréless-twist engineering across a wide range of van der Waals heterostructures.
Electronic properties and materials, Superconducting properties and materials
PLA2G15 is a BMP hydrolase and its targeting ameliorates lysosomal disease
Original Paper | Hydrolases | 2025-05-06 20:00 EDT
Kwamina Nyame, Jian Xiong, Hisham N. Alsohybe, Arthur P. H. de Jong, Isabelle V. Peña, Ricardo de Miguel, Thijn R. Brummelkamp, Guido Hartmann, Sebastian M. B. Nijman, Matthijs Raaben, Judith A. Simcox, Vincent A. Blomen, Monther Abu-Remaileh
Lysosomes catabolize lipids and other biological molecules, maintaining cellular and organismal homeostasis. Bis(monoacylglycero)phosphate (BMP), a major lipid constituent of intralysosomal vesicles, stimulates lipid-degrading enzymes and is altered in various human conditions, including neurodegenerative diseases1,2. Although lysosomal BMP synthase was recently discovered3, the enzymes mediating BMP turnover remain elusive. Here we show that lysosomal phospholipase PLA2G15 is a physiological BMP hydrolase. We further demonstrate that the resistance of BMP to lysosomal hydrolysis arises from its unique sn2, sn2’ esterification position and stereochemistry, as neither feature alone confers resistance. Purified PLA2G15 catabolizes most BMP species derived from cell and tissue lysosomes. Furthermore, PLA2G15 efficiently hydrolyses synthesized BMP stereoisomers with primary esters, challenging the long-held thought that BMP stereochemistry alone ensures resistance to acid phospholipases. Conversely, BMP with secondary esters and S,S stereoconfiguration is stable in vitro and requires acyl migration for hydrolysis in lysosomes. Consistent with our biochemical data, PLA2G15-deficient cells and tissues accumulate several BMP species, a phenotype reversible by supplementing wild-type PLA2G15 but not its inactive mutant. Targeting PLA2G15 reduces the cholesterol accumulation in fibroblasts of patients with Niemann-Pick disease type C1 and significantly ameliorates disease pathologies in Niemann-Pick disease type C1-deficient mice, leading to an extended lifespan. Our findings established the rules governing BMP stability in lysosomes and identified PLA2G15 as a lysosomal BMP hydrolase and a potential target for therapeutic intervention in neurodegenerative diseases.
Hydrolases, Lysosomes
Bioremediation of complex organic pollutants by engineered Vibrio natriegens
Original Paper | Environmental biotechnology | 2025-05-06 20:00 EDT
Cong Su, Haotian Cui, Weiwei Wang, Yong Liu, Zhenyu Cheng, Chen Wang, Mengqiao Yang, Liwen Qu, Ye Li, Yuejin Cai, Siyang He, Jiaxin Zheng, Pingping Zhao, Ping Xu, Junbiao Dai, Hongzhi Tang
Industrial wastewater, petroleum pollution and plastic contamination are significant threats to global marine biosecurity because of their toxic, mutagenic and persistent nature1. The use of microorganisms in bioremediation has been constrained by the complexity of organic pollutants and limited tolerance to saline stress2. In this study, we used synthetic biology to engineer Vibrio natriegens into a strain capable of bioremediating complex organic pollutants in saline wastewater and soils. The competence master regulator gene tfoX was inserted into chromosome 1 of the V. natriegens strain Vmax and overexpressed to enhance DNA uptake and integration. Degradation gene clusters were chemically synthesized and assembled in yeast. We developed a genome engineering method (iterative natural transformation based on Vmax with amplified tfoX effect) to transfer five gene clusters (43 kb total) into Vmax. The engineered strain has the ability to bioremediate five organic pollutants (biphenyl, phenol, naphthalene, dibenzofuran and toluene) covering a broad substrate range, from monocyclic to multicyclic compounds, in industrial wastewater samples from a chlor-alkali plant and a petroleum refinery.
Environmental biotechnology, Water microbiology
Intragrain 3D perovskite heterostructure for high-performance pure-red perovskite LEDs
Original Paper | Inorganic LEDs | 2025-05-06 20:00 EDT
Yong-Hui Song, Bo Li, Zi-Jian Wang, Xiao-Lin Tai, Guan-Jie Ding, Zi-Du Li, Huaiyu Xu, Jing-Ming Hao, Kuang-Hui Song, Li-Zhe Feng, Ya-Lan Hu, Yi-Chen Yin, Bai-Sheng Zhu, Guozhen Zhang, Huanxin Ju, Guanhaojie Zheng, Wei Hu, Yue Lin, Fengjia Fan, Hong-Bin Yao
Metal-halide perovskites are promising light-emitter candidates for next-generation light-emitting diodes (LEDs)1,2,3,4,5,6,7,8. Achieving high brightness and efficiency simultaneously in pure-red perovskite LEDs (PeLEDs) is an ongoing goal9,10. Three-dimensional (3D) CsPbI3-xBrx emitters have excellent carrier transport capability and high colour purity, which could allow efficient and ultrabright pure-red PeLEDs. However, such devices are prone to efficiency roll-off, resulting in low efficiency and low brightness under high current density. Here, by using electrically excited transient absorption spectroscopy, we discovered the efficiency roll-off was induced by hole leakage. Therefore, we developed a CsPbI3-xBrx intragrain heterostructure containing narrow bandgap emitters and wide bandgap barriers to confine the injected carriers. The wide bandgap barrier was incorporated by introducing strongly bonding molecules into the [PbX6]4- framework to expand the 3D CsPbI3-xBrx lattice. This strategy resulted in bright and efficient pure-red PeLEDs, with a high brightness of 24,600 cd m-2, maximum external quantum efficiency of 24.2% and low efficiency roll-off, maintaining a 10.5% external quantum efficiency at a high luminance of 22,670 cd m-2.
Inorganic LEDs
Light-microscopy-based connectomic reconstruction of mammalian brain tissue
Original Paper | 3-D reconstruction | 2025-05-06 20:00 EDT
Mojtaba R. Tavakoli, Julia Lyudchik, Michał Januszewski, Vitali Vistunou, Nathalie Agudelo Dueñas, Jakob Vorlaufer, Christoph Sommer, Caroline Kreuzinger, Bárbara Oliveira, Alban Cenameri, Gaia Novarino, Viren Jain, Johann G. Danzl
The information-processing capability of the brain’s cellular network depends on the physical wiring pattern between neurons and their molecular and functional characteristics. Mapping neurons and resolving their individual synaptic connections can be achieved by volumetric imaging at nanoscale resolution1,2 with dense cellular labelling. Light microscopy is uniquely positioned to visualize specific molecules, but dense, synapse-level circuit reconstruction by light microscopy has been out of reach, owing to limitations in resolution, contrast and volumetric imaging capability. Here we describe light-microscopy-based connectomics (LICONN). We integrated specifically engineered hydrogel embedding and expansion with comprehensive deep-learning-based segmentation and analysis of connectivity, thereby directly incorporating molecular information into synapse-level reconstructions of brain tissue. LICONN will allow synapse-level phenotyping of brain tissue in biological experiments in a readily adoptable manner.
3-D reconstruction, Cellular neuroscience, Confocal microscopy, Neural circuits, Super-resolution microscopy
Oncogene aberrations drive medulloblastoma progression, not initiation
Original Paper | CNS cancer | 2025-05-06 20:00 EDT
Konstantin Okonechnikov, Piyush Joshi, Verena Körber, Anne Rademacher, Michele Bortolomeazzi, Jan-Philipp Mallm, Jan Vaillant, Patricia Benites Goncalves da Silva, Britta Statz, Mari Sepp, Ioannis Sarropoulos, Tetsuya Yamada, Andrea Wittmann, Kathrin Schramm, Mirjam Blattner-Johnson, Petra Fiesel, Barbara Jones, Natalie Jäger, Till Milde, Kristian W. Pajtler, Cornelis M. van Tilburg, Olaf Witt, Konrad Bochennek, Katharina Johanna Weber, Lisa Nonnenmacher, Christian Reimann, David R. Ghasemi, Ulrich Schüller, Martin Mynarek, Stefan Rutkowski, David T. W. Jones, Andrey Korshunov, Karsten Rippe, Frank Westermann, Supat Thongjuea, Thomas Höfer, Henrik Kaessmann, Lena M. Kutscher, Stefan M. Pfister
Despite recent advances in understanding disease biology, treatment of group 3/4 medulloblastoma remains a therapeutic challenge in paediatric neuro-oncology1. Bulk-omics approaches have identified considerable intertumoural heterogeneity in group 3/4 medulloblastoma, including the presence of clear single-gene oncogenic drivers in only a subset of cases, whereas in most cases, large-scale copy number aberrations prevail2,3. However, intratumoural heterogeneity, the role of oncogene aberrations, and broad copy number variation in tumour evolution and treatment resistance remain poorly understood. To dissect this interplay, we used single-cell technologies (single-nucleus RNA sequencing (snRNA-seq), single-nucleus assay for transposase-accessible chromatin with high-throughput sequencing (snATAC-seq) and spatial transcriptomics) on a cohort of group 3/4 medulloblastoma with known alterations in the oncogenes MYC, MYCN and PRDM6. We show that large-scale chromosomal aberrations are early tumour-initiating events, whereas the single-gene oncogenic events arise late and are typically subclonal, but MYC can become clonal upon disease progression to drive further tumour development and therapy resistance. Spatial transcriptomics shows that the subclones are mostly interspersed across tumour tissue, but clear segregation is also present. Using a population genetics model, we estimate medulloblastoma initiation in the cerebellar unipolar brush cell lineage starting from the first gestational trimester. Our findings demonstrate how single-cell technologies can be applied for early detection and diagnosis of this fatal disease.
CNS cancer, Data processing
Striatum supports fast learning but not memory recall
Original Paper | Learning and memory | 2025-05-06 20:00 EDT
Kimberly Reinhold, Marci Iadarola, Shi Tang, Annabel Chang, Whitney Kuwamoto, Madeline A. Albanese, Senmiao Sun, Richard Hakim, Joshua Zimmer, Wengang Wang, Bernardo L. Sabatini
Animals learn to carry out motor actions in specific sensory contexts to achieve goals. The striatum has been implicated in producing sensory-motor associations1, yet its contributions to memory formation and recall are not clear. Here, to investigate the contribution of the striatum to these processes, mice were taught to associate a cue, consisting of optogenetic activation of striatum-projecting neurons in visual cortex, with the availability of a food pellet that could be retrieved by forelimb reaching. As necessary to direct learning, striatal neural activity encoded both the sensory context and the outcome of reaching. With training, the rate of cued reaching increased, but brief optogenetic inhibition of striatal activity arrested learning and prevented trial-to-trial improvements in performance. However, the same manipulation did not affect performance improvements already consolidated into short-term (less than 1 h) or long-term (days) memories. Hence, striatal activity is necessary for trial-to-trial improvements in performance, leading to plasticity in other brain areas that mediate memory recall.
Learning and memory, Sensorimotor processing
Heterogeneous pericoerulear neurons tune arousal and exploratory behaviours
Original Paper | Cellular neuroscience | 2025-05-06 20:00 EDT
Andrew T. Luskin, Li Li, Xiaonan Fu, Madison M. Martin, Kelsey Barcomb, Kasey S. Girven, Taylor Blackburn, Bailey A. Wells, Sarah T. Thai, Esther M. Li, Akshay N. Rana, Rhiana C. Simon, Li Sun, Lei Gao, Alexandria D. Murry, Sam A. Golden, Garret D. Stuber, Christopher P. Ford, Liangcai Gu, Michael R. Bruchas
As the primary source of noradrenaline in the brain, the locus coeruleus (LC) regulates arousal, avoidance and stress responses1,2. However, how local neuromodulatory inputs control LC function remains unresolved. Here we identify a population of transcriptionally, spatially and functionally diverse GABAergic (γ-aminobutyric acid-producing) neurons in the LC dendritic field that receive distant inputs and modulate modes of LC firing to control global arousal levels and arousal-related processing and behaviours. We define peri-LC anatomy using viral tracing and combine single-cell RNA sequencing with spatial transcriptomics to molecularly define both LC noradrenaline-producing and peri-LC cell types. We identify several neuronal cell types that underlie peri-LC functional diversity using a series of complementary neural circuit approaches in behaving mice. Our findings indicate that LC and peri-LC neurons are transcriptionally, functionally and anatomically heterogenous neuronal populations that modulate arousal and avoidance states. Defining the molecular, cellular and functional diversity of the LC and peri-LC provides a roadmap for understanding the neurobiological basis of arousal, motivation and neuropsychiatric disorders.
Cellular neuroscience, Genetics of the nervous system, Locus coeruleus, Neural circuits, Stress and resilience
Dopamine D1-D2 signalling in hippocampus arbitrates approach and avoidance
Original Paper | Cellular neuroscience | 2025-05-06 20:00 EDT
Arthur Godino, Marine Salery, Angelica M. Minier-Toribio, Vishwendra Patel, John F. Fullard, Veronika Kondev, Eric M. Parise, Freddyson J. Martinez-Rivera, Carole Morel, Panos Roussos, Robert D. Blitzer, Eric J. Nestler
The hippocampus1,2,3,4,5,6, as well as dopamine circuits7,8,9, coordinates decision-making in anxiety-eliciting situations. Yet, little is known about how dopamine modulates hippocampal representations of emotionally salient stimuli to inform appropriate resolution of approach versus avoidance conflicts. Here we studied dopaminoceptive neurons in the male mouse ventral hippocampus (vHipp), molecularly distinguished by their expression of dopamine D1 or D2 receptors. We show that these neurons are transcriptionally distinct and topographically organized across vHipp subfields and cell types. In the ventral subiculum where they are enriched, both D1 and D2 neurons are recruited during anxiogenic exploration, yet with distinct profiles related to investigation and behavioural selection. In turn, they mediate opposite approach-avoidance responses, and are differentially modulated by dopaminergic transmission in that region. Together, these results suggest that vHipp dopamine dynamics gate exploratory behaviours under contextual uncertainty, implicating dopaminoception in the complex computation engaged in the vHipp to govern emotional states.
Cellular neuroscience, Emotion, Neural circuits, Neurophysiology
Targeting the SHOC2-RAS interaction in RAS-mutant cancers
Original Paper | Cancer | 2025-05-06 20:00 EDT
Zachary J. Hauseman, Frédéric Stauffer, Kim S. Beyer, Sandra Mollé, Elena Cavicchioli, Jean-Remy Marchand, Michelle Fodor, Jessica Viscomi, Anxhela Dhembi, Stéphanie Katz, Beatrice Faggion, Mylene Lanter, Grainne Kerr, Daniela Schildknecht, Cornelia Handl, Danilo Maddalo, Carole Pissot Soldermann, Jacob Brady, Om Shrestha, Zachary Nguyen, Lukas Leder, Gregor Cremosnik, Sandra Lopez Romero, Ulrich Hassiepen, Travis Stams, Markus Linder, Giorgio G. Galli, Daniel A. Guthy, Daniel A. King, Sauveur-Michel Maira, Claudio R. Thoma, Veronika Ehmke, Luca Tordella
Activating mutations in the rat sarcoma (RAS) genes HRAS, NRAS and KRAS collectively represent the most frequent oncogenic driver in human cancer1. They have previously been considered undruggable, but advances in the past few years have led to the clinical development of agents that target KRAS(G12C) and KRAS(G12D) mutants, yielding promises of therapeutic responses at tolerated doses2. However, clinical agents that selectively target NRAS(Q61*) mutants (* represents ‘any’), the second-most-frequent oncogenic driver in melanoma, are still lacking. Here we identify SHOC2, a component of the SHOC2-MRAS-PP1C complex, as a dependency of RAS(Q61*) tumours in a nucleotide-state-dependent and isoform-agnostic manner. Mechanistically, we found that oncogenic NRAS(Q61R) forms a direct interaction with SHOC2, evidenced by X-ray co-crystal structure. In vitro high-throughput screening enabled the discovery of small molecules that bind to SHOC2 and disrupt the interaction with NRAS(Q61*). Structure-based optimization led to a cellularly active tool compound that shows inhibition of mitogen-activated protein kinase (MAPK) signalling and proliferation in RAS-mutant cancer models, most notably in NRAS(Q61*) settings. These findings provide evidence for a neomorph SHOC2-(canonical)RAS protein interaction that is pharmacologically actionable and relevant to cancer sustenance. Overall, this work provides the concept validation and foundation for developing new therapies at the core of the RAS signalling pathway.
Cancer, Medicinal chemistry, X-ray crystallography
Herring spawned poleward following fishery-induced collective memory loss
Original Paper | Animal migration | 2025-05-06 20:00 EDT
Aril Slotte, Are Salthaug, Sindre Vatnehol, Espen Johnsen, Erik Askov Mousing, Åge Høines, Cecilie Thorsen Broms, Sigurvin Bjarnason, Eydna í Homrum, Øystein Skagseth, Erling Kåre Stenevik
Entrainment is a process in schooling migratory fish whereby routes to suitable habitats are transferred from repeat spawners to recruits over generations through social learning1. Selective fisheries targeting older fish may therefore result in collective memory loss and disrupted migration culture2. The world’s largest herring (Clupea harengus) population has traditionally migrated up to 1,300 km southward from wintering areas in northern Norwegian waters to spawn at the west coast. This conservative strategy is proposed to be a trade-off between high energetic swimming costs and enhanced larval survival under improved growth conditions3. Here an analysis of extensive data from fisheries, scientific surveys and tagging experiments demonstrates an abrupt approximately 800-km poleward shift in main spawning. The new migration was established by a large cohort recruiting when the abundance of older fish was critically low due to age-selective fisheries. The threshold of memory required for cultural transfer was probably not met–a situation that was further exacerbated by reduced spatiotemporal overlap between older fish and recruits driven by migration constraints and climate change. Finally, a minority of survivors from older generations adopted the migration culture from the recruits instead of the historically opposite. This may have profound consequences for production and coastal ecology, challenging the management of migratory schooling fish.
Animal migration, Behavioural ecology, Population dynamics
Trends in the seasonal amplitude of atmospheric methane
Original Paper | Biogeochemistry | 2025-05-06 20:00 EDT
Gang Liu, Lu Shen, Philippe Ciais, Xin Lin, Didier Hauglustaine, Xin Lan, Alexander J. Turner, Yi Xi, Yu Zhu, Shushi Peng
Methane is an important greenhouse gas1 and its atmospheric concentration has almost tripled since pre-industrial times2,3,4. Atmospheric methane mixing ratios vary seasonally, with the seasonal cycle amplitude (SCA) having decreased in northern high latitudes and increased in the subtropics and tropics since the 1980s5,6. These opposing SCA trends can help understanding of long-term changes in the global methane budget, as methane emissions and sinks have opposing effects on the SCA5. However, trends in the methane SCA have not yet been explored in detail5,6. Here we use a suite of atmospheric transport model simulations and attribute the observed trends in the seasonal amplitude of methane to changes in emissions and the atmospheric sink from reaction with the hydroxyl radical (OH). We find that the decreasing amplitude in the northern high latitudes is mainly caused by an increase in natural emissions (such as wetlands) owing to a warmer climate, adding evidence to previous studies suggesting a positive climate feedback7,8,9. In contrast, the enhanced methane amplitude in the subtropics and tropics is mainly attributed to strengthened OH oxidation. Our results provide independent evidence for an increase in tropospheric OH concentration10,11 of 10 ± 1% since 1984, which together with an increasing atmospheric methane concentration suggests a 21 ± 1% increase in the atmospheric methane sink.
Biogeochemistry, Climate sciences
Native nucleosomes intrinsically encode genome organization principles
Original Paper | Chromatin structure | 2025-05-06 20:00 EDT
Sangwoo Park, Raquel Merino-Urteaga, Violetta Karwacki-Neisius, Gustavo Ezequiel Carrizo, Advait Athreya, Alberto Marin-Gonzalez, Nils A. Benning, Jonghan Park, Michelle M. Mitchener, Natarajan V. Bhanu, Benjamin A. Garcia, Bin Zhang, Tom W. Muir, Erika L. Pearce, Taekjip Ha
The eukaryotic genome is packed into nucleosomes of 147 base pairs around a histone core and is organized into euchromatin and heterochromatin, corresponding to the A and B compartments, respectively1,2. Here we investigated whether individual nucleosomes contain sufficient information for 3D genomic organization into compartments, for example, in their biophysical properties. We purified native mononucleosomes to high monodispersity and used physiological concentrations of polyamines to determine their condensability. The chromosomal regions known to partition into A compartments have low condensability and those for B compartments have high condensability. Chromatin polymer simulations using condensability as the only input, without any trans factors, reproduced the A/B compartments. Condensability is also strongly anticorrelated with gene expression, particularly near the promoters and in a cell type-dependent manner. Therefore, mononucleosomes have biophysical properties associated with genes being on or off. Comparisons with genetic and epigenetic features indicate that nucleosome condensability is an emergent property, providing a natural axis on which to project the high-dimensional cellular chromatin state. Analysis using various condensing agents or histone modifications and mutations indicates that the genome organization principle encoded into nucleosomes is mostly electrostatic in nature. Polyamine depletion in mouse T cells, resulting from either knocking out or inhibiting ornithine decarboxylase, results in hyperpolarized condensability, indicating that when cells cannot rely on polyamines to translate the biophysical properties of nucleosomes to 3D genome organization, they accentuate condensability contrast, which may explain the dysfunction observed with polyamine deficiency3,4,5.
Chromatin structure, Supramolecular assembly
Superconductivity and spin canting in spin-orbit-coupled trilayer graphene
Original Paper | Magnetic properties and materials | 2025-05-06 20:00 EDT
Caitlin L. Patterson, Owen I. Sheekey, Trevor B. Arp, Ludwig F. W. Holleis, Jin Ming Koh, Youngjoon Choi, Tian Xie, Siyuan Xu, Yi Guo, Hari Stoyanov, Evgeny Redekop, Canxun Zhang, Grigory Babikyan, David Gong, Haoxin Zhou, Xiang Cheng, Takashi Taniguchi, Kenji Watanabe, Martin E. Huber, Chenhao Jin, Étienne Lantagne-Hurtubise, Jason Alicea, Andrea F. Young
Graphene and transition metal dichalcogenide flat-band systems show similar phase diagrams, replete with magnetic1,2,3,4,5 and superconducting6,7,8,9,10,11 phases. An abiding question has been whether magnetic ordering competes with superconductivity or facilitates pairing. For example, recent studies of Bernal bilayer graphene in the presence of enhanced spin-orbit coupling show a substantial increase in the observed domain and critical temperature Tc of superconducting states12,13,14; however, the mechanism for this enhancement remains unknown. Here we show that introducing spin-orbit coupling in rhombohedral trilayer graphene (RTG) by substrate proximity effect generates new superconducting pockets for both electron and hole doping, with maximal Tc ≈ 300 mK, which is three times larger than in RTG encapsulated by hexagonal boron nitride. Using local magnetometry, we show that superconductivity straddles a transition between a spin-canted state with a finite in-plane magnetic moment and a state with complete spin-valley locking. This transition is reproduced in our Hartree-Fock calculations, in which this transition is driven by the competition between spin-orbit coupling and the carrier-density-tuned Hund’s interaction. Our experiment suggests that the enhancement of superconductivity by spin-orbit coupling is driven by a quantitative change in the canting angle rather than a change in the ground state symmetry. These results align with a recently proposed mechanism for the enhancement of superconductivity15, in which fluctuations in the spin-canting order contribute to the pairing interaction.
Magnetic properties and materials, Superconducting properties and materials
Deep origin of eukaryotes outside Heimdallarchaeia within Asgardarchaeota
Original Paper | Archaeal evolution | 2025-05-06 20:00 EDT
Jiawei Zhang, Xiaoyuan Feng, Meng Li, Yang Liu, Min Liu, Li-Jun Hou, Hong-Po Dong
Research on the morphology, physiology and genomics of Asgard archaea has provided valuable insights into the evolutionary history of eukaryotes1,2,3. A previous study suggested that eukaryotes are nested within Heimdallarchaeia4, but their exact phylogenetic placement within Asgard archaea remains controversial4,5. This debate complicates understanding of the metabolic features and timescales of early eukaryotic ancestors. Here we generated 223 metagenome-assembled nearly complete genomes of Asgard archaea that have not previously been documented. We identify 16 new lineages at the genus level or higher, which substantially expands the known phylogenetic diversity of Asgard archaea. Through sophisticated phylogenomic analysis of this expanded genomic dataset involving several marker sets we infer that eukaryotes evolved before the diversification of all sampled Heimdallarchaeia, rather than branching with Hodarchaeales within the Heimdallarchaeia. This difference in the placement of eukaryotes is probably caused by the previously underappreciated chimeric nature of Njordarchaeales genomes, which we find are composed of sequences of both Asgard and TACK archaea (Asgard’s sister phylum). Using ancestral reconstruction and molecular dating, we infer that the last Asgard archaea and eukaryote common ancestor emerged before the Great Oxidation Event and was probably an anaerobic H2-dependent acetogen. Our findings support the hydrogen hypothesis of eukaryogenesis, which posits that eukaryotes arose from the fusion of a H2-consuming archaeal host and a H2-producing protomitochondrion.
Archaeal evolution, Archaeal genomics, Evolutionary genetics, Metagenomics, Phylogenetics
Activation of lysosomal iron triggers ferroptosis in cancer
Original Paper | Cancer therapeutic resistance | 2025-05-06 20:00 EDT
Tatiana Cañeque, Leeroy Baron, Sebastian Müller, Alanis Carmona, Ludovic Colombeau, Antoine Versini, Stéphanie Solier, Christine Gaillet, Fabien Sindikubwabo, Julio L. Sampaio, Marie Sabatier, Eikan Mishima, Armel Picard-Bernes, Laurène Syx, Nicolas Servant, Bérangère Lombard, Damarys Loew, Jiashuo Zheng, Bettina Proneth, Leishemba K. Thoidingjam, Laurence Grimaud, Cameron S. Fraser, Krystina J. Szylo, Emma Der Kazarian, Caroline Bonnet, Emmanuelle Charafe-Jauffret, Christophe Ginestier, Patricia Santofimia-Castaño, Matias Estaras, Nelson Dusetti, Juan Lucio Iovanna, Antonio Sa Cunha, Gabriella Pittau, Pascal Hammel, Dimitri Tzanis, Sylvie Bonvalot, Sarah Watson, Vincent Gandon, Aditya Upadhyay, Derek A. Pratt, Florêncio Porto Freitas, José Pedro Friedmann Angeli, Brent R. Stockwell, Marcus Conrad, Jessalyn M. Ubellacker, Raphaël Rodriguez
Iron catalyses the oxidation of lipids in biological membranes and promotes a form of cell death called ferroptosis1. Defining where this chemistry occurs in the cell can inform the design of drugs capable of inducing or inhibiting ferroptosis in various disease-relevant settings. Genetic approaches have revealed suppressors of ferroptosis2,3,4; by contrast, small molecules can provide spatiotemporal control of the chemistry at work5. Here we show that the ferroptosis inhibitor liproxstatin-1 exerts cytoprotective effects by inactivating iron in lysosomes. We also show that the ferroptosis inducer RSL3 initiates membrane lipid oxidation in lysosomes. We designed a small-molecule activator of lysosomal iron–fentomycin-1–to induce the oxidative degradation of phospholipids and ultimately ferroptosis. Fentomycin-1 is able to kill iron-rich CD44high primary sarcoma and pancreatic ductal adenocarcinoma cells, which can promote metastasis and fuel drug tolerance. In such cells, iron regulates cell adaptation6,7 while conferring vulnerability to ferroptosis8,9. Sarcoma cells exposed to sublethal doses of fentomycin-1 acquire a ferroptosis-resistant cell state characterized by the downregulation of mesenchymal markers and the activation of a membrane-damage response. This phospholipid degrader can eradicate drug-tolerant persister cancer cells in vitro and reduces intranodal tumour growth in a mouse model of breast cancer metastasis. Together, these results show that control of iron reactivity confers therapeutic benefits, establish lysosomal iron as a druggable target and highlight the value of targeting cell states10.
Cancer therapeutic resistance, Iron, Lipidomics, Small molecules
Nasal vaccines for respiratory infections
Review Paper | Infection | 2025-05-06 20:00 EDT
Hiroshi Kiyono, Peter B. Ernst
Beginning with Edward Jenner’s discovery of the smallpox vaccine, the ever-expanding repertoire of vaccines against pathogens has saved many lives. During the COVID-19 pandemic, a revolutionary mRNA injectable vaccine emerged that effectively controlled the severity of disease caused by SARS-CoV-2. This vaccine induced potent antigen-specific neutralizing serum IgG antibodies, but was limited in its ability to prevent viral invasion at the respiratory surfaces. Nasal vaccines have attracted attention as a potential strategy to combat respiratory infections and prepare for future pandemics. Input from disciplines such as microbiology, biomaterials, bioengineering and chemistry have complemented the immunology to create innovative delivery systems. This approach to vaccine delivery has yielded nasal vaccines that induce secretory IgA as well as serum IgG antibodies, which are expected to prevent pathogen invasion, thereby diminishing transmission and disease severity. For a nasal vaccine to be successful, the complexity of the relevant anatomical, physiological and immunological properties, including the proximity of the central nervous system to the nasal cavity, must be considered. In this Review, we discuss past and current efforts as well as future directions for developing safe and effective nasal vaccines for the prevention of respiratory infections.
Infection, Mucosal immunology, Vaccines
Motor learning refines thalamic influence on motor cortex
Original Paper | Motor cortex | 2025-05-06 20:00 EDT
Assaf Ramot, Felix H. Taschbach, Yun C. Yang, Yuxin Hu, Qiyu Chen, Bobbie C. Morales, Xinyi C. Wang, An Wu, Kay M. Tye, Marcus K. Benna, Takaki Komiyama
The primary motor cortex (M1) is central for the learning and execution of dexterous motor skills1,2,3, and its superficial layer (layers 2 and 3; hereafter, L2/3) is a key locus of learning-related plasticity1,4,5,6. It remains unknown how motor learning shapes the way in which upstream regions activate M1 circuits to execute learned movements. Here, using longitudinal axonal imaging of the main inputs to M1 L2/3 in mice, we show that the motor thalamus is the key input source that encodes learned movements in experts (animals trained for two weeks). We then use optogenetics to identify the subset of M1 L2/3 neurons that are strongly driven by thalamic inputs before and after learning. We find that the thalamic influence on M1 changes with learning, such that the motor thalamus preferentially activates the M1 neurons that encode learned movements in experts. Inactivation of the thalamic inputs to M1 in experts impairs learned movements. Our study shows that motor learning reshapes the thalamic influence on M1 to enable the reliable execution of learned movements.
Motor cortex, Neural decoding
A cryptic role for reciprocal helping in a cooperatively breeding bird
Original Paper | Evolutionary ecology | 2025-05-06 20:00 EDT
Alexis D. Earl, Gerald G. Carter, Arden G. Berlinger, Elkana Korir, Shailee S. Shah, Wilson N. Watetu, Dustin R. Rubenstein
Identifying the mechanisms that underlie cooperation is fundamental to biology1. The most complex form of cooperation in vertebrates occurs in cooperative breeders, in which helpers forego reproduction and assist in raising the young of others, typically relatives2. Not all cooperative societies, however, are kin-based–nearly half of all avian3 and mammalian4 cooperative breeders form mixed-kin societies, much like those of humans5. Kin selection in mixed-kin societies occurs when individuals gain indirect fitness from the preferential helping of relatives6, but helpers also frequently assist non-kin7, highlighting a potential role for direct fitness in stabilizing cooperative societies7,8. Here, using a 20-year study of superb starlings (Lamprotornis superbus), we examined how direct and indirect fitness jointly influence helping behaviour. Although we detected kin-biased helping (demonstrating kin selection), non-kin helping was common despite opportunities to aid kin. Unexpectedly, specific pairs maintained long-term reciprocal helping relationships by swapping social roles across their lifetimes–a subtle pattern of reciprocity requiring decades of observation to detect. Given the frequency of non-kin helping and the occurrence of reciprocal helping among both kin and non-kin, helping behaviour in superb starlings seems to be greatly influenced by direct fitness. However, the relative importance of direct and indirect fitness varied with helpers’ sex and dispersal history. By uncovering a cryptic yet crucial role of long-term reciprocal helping, we suggest that reciprocity may be an underappreciated mechanism promoting the stability of cooperatively breeding societies.
Evolutionary ecology, Social evolution
Chromatin loops are an ancestral hallmark of the animal regulatory genome
Original Paper | Chromatin structure | 2025-05-06 20:00 EDT
Iana V. Kim, Cristina Navarrete, Xavier Grau-Bové, Marta Iglesias, Anamaria Elek, Grygoriy Zolotarov, Nikolai S. Bykov, Sean A. Montgomery, Ewa Ksiezopolska, Didac Cañas-Armenteros, Joan J. Soto-Angel, Sally P. Leys, Pawel Burkhardt, Hiroshi Suga, Alex de Mendoza, Marc A. Marti-Renom, Arnau Sebé-Pedrós
In bilaterian animals, gene regulation is shaped by a combination of linear and spatial regulatory information. Regulatory elements along the genome are integrated into gene regulatory landscapes through chromatin compartmentalization1,2, insulation of neighbouring genomic regions3,4 and chromatin looping that brings together distal cis-regulatory sequences5. However, the evolution of these regulatory features is unknown because the three-dimensional genome architecture of most animal lineages remains unexplored6,7. To trace the evolutionary origins of animal genome regulation, here we characterized the physical organization of the genome in non-bilaterian animals (sponges, ctenophores, placozoans and cnidarians)8,9 and their closest unicellular relatives (ichthyosporeans, filastereans and choanoflagellates)10 by combining high-resolution chromosome conformation capture11,12 with epigenomic marks and gene expression data. Our comparative analysis showed that chromatin looping is a conserved feature of genome architecture in ctenophores, placozoans and cnidarians. These sequence-determined distal contacts involve both promoter-enhancer and promoter-promoter interactions. By contrast, chromatin loops are absent in the unicellular relatives of animals. Our findings indicate that spatial genome regulation emerged early in animal evolution. This evolutionary innovation introduced regulatory complexity, ultimately facilitating the diversification of animal developmental programmes and cell type repertoires.
Chromatin structure, Comparative genomics, Evolution, Gene regulation
Nature Reviews Materials
Biomaterials in cellular agriculture and plant-based foods for the future
Review Paper | Biomaterials - cells | 2025-05-06 20:00 EDT
Edward B. Gordon, Inyoung Choi, Armaghan Amanipour, Yiwen Hu, Amin Nikkhah, Begum Koysuren, Champ Jones, Nitin Nitin, Reza Ovissipour, Markus J. Buehler, Nicole Tichenor Blackstone, David L. Kaplan
Alternative food products are needed to address the most pressing challenges faced by the food industry: growing global food demand, health concerns, animal welfare, food security and environmental sustainability. Future foods are defined as foods with scalability and sustainability potential owing to rapidly advancing technological developments in their production systems. Key areas of study for future foods include cellular agriculture and plant-based systems, which include biomaterials as key ingredients or as structural components to impart texture, support cell growth and metabolism, and provide nutrients and organoleptic factors to food products. This Review discusses current requirements, options and processing approaches for biomaterials with utility in future foods. We focus on two main approaches: cellular agriculture wherein the cells are the key component for food (with the biomaterials utilized to support the cells via adherence and/or for texture) and plant-based foods wherein acellular plant-derived biomaterials are the food components. In both cases, the same fundamental challenges apply for the biomaterials: achieving utility at scale and low cost while meeting food safety requirements. Other considerations for biomaterials for future foods are also addressed, including sustainability, modelling, consumer acceptance, nutrition, regulatory status and safety considerations to highlight the path ahead. This emerging field of biomaterials for future foods offers a new generation of biomaterial systems that can positively impact human health, environmental sustainability and animal welfare. Although scaling these biomaterial sources cost-effectively presents a major challenge, substantial progress is being made, and opportunities to establish supply chains are already underway.
Biomaterials - cells
Physical Review Letters
Topological Quantum Batteries
Research article | Batteries | 2025-05-06 06:00 EDT
Zhi-Guang Lu, Guoqing Tian, Xin-You Lü, and Cheng Shang
We propose an innovative design for quantum batteries (QBs) that involves coupling two-level systems to a topological photonic waveguide. Employing the resolvent method, we analytically explore the thermodynamic performance of QBs. First, we demonstrate that in the long-time limit, only bound states significantly contribute to the stored energy of QBs. We observe that near-perfect energy transfer can occur in the topologically nontrivial phase. Moreover, the maximum stored energy exhibits singular behavior at the phase boundaries, where the number of bound states undergoes a transition. Second, when a quantum charger and a quantum battery are coupled at the same sublattice within a unit cell, the ergotropy becomes immune to dissipation at that location, facilitated by a dark state and a topologically robust dressed bound state. Third, we show that as dissipation intensifies along with the emergence of the quantum Zeno effect, the charging power of QBs experiences a temporary boost. Our findings offer valuable guidance for improving quantum battery performance in realistic conditions through structured reservoir engineering.
Phys. Rev. Lett. 134, 180401 (2025)
Batteries, Quantum control, Quantum description of light-matter interaction, Quantum thermodynamics, Topological effects in photonic systems
Strict Area Law Entanglement versus Chirality
Research article | Entanglement entropy | 2025-05-06 06:00 EDT
Xiang Li, Ting-Chun Lin, John McGreevy, and Bowen Shi
Chirality is a property of a gapped phase of matter in two spatial dimensions that can be manifested through nonzero thermal or electrical Hall conductance. In this Letter, we prove two no-go theorems that forbid such chirality for a quantum state in a finite dimensional local Hilbert space with strict area law entanglement entropies. We also show that the finite dimensional local Hilbert space condition can be relaxed to the condition that the state has finite local entanglement entropies. As a crucial ingredient in the proofs, we introduce a new quantum information-theoretic primitive called instantaneous modular flow, which has many other potential applications.
Phys. Rev. Lett. 134, 180402 (2025)
Entanglement entropy, Entanglement in field theory, Fractional quantum Hall effect, Integer quantum Hall effect, Quantum information theory
Optimal Conversion from Classical to Quantum Randomness via Quantum Chaos
Research article | Eigenstate thermalization | 2025-05-06 06:00 EDT
Wai-Keong Mok, Tobias Haug, Adam L. Shaw, Manuel Endres, and John Preskill
Quantum many-body systems provide a unique platform for exploring the rich interplay between chaos, randomness, and complexity. In a recently proposed paradigm known as deep thermalization, random quantum states of system $A$ are generated by performing projective measurements on system $B$ following chaotic Hamiltonian evolution acting jointly on $AB$. In this scheme, the randomness of the projected state ensemble arises from the intrinsic randomness of the outcomes when $B$ is measured. Here, we propose a modified scheme in which classical randomness injected during the protocol is converted by quantum chaos into quantum randomness of the resulting state ensemble. We show that for generic chaotic systems this conversion is optimal in that each bit of injected classical entropy generates as much additional quantum randomness as adding an extra qubit to $B$. This significantly enhances the randomness of the projected ensemble without imposing additional demands on the quantum hardware. Our scheme can be easily implemented on typical analog quantum simulators, providing a more scalable route for generating quantum randomness valuable for many applications. In particular, we demonstrate that the accuracy of a shadow tomography protocol can be substantially improved.
Phys. Rev. Lett. 134, 180403 (2025)
Eigenstate thermalization, Quantum chaos, Quantum correlations in quantum information, Quantum information processing, Quantum quench, Quantum tomography, Quantum many-body systems
Robust Approach for Time-Bin-Encoded Photonic Quantum Information Protocols
Research article | Optical quantum information processing | 2025-05-06 06:00 EDT
Simon J. U. White, Emanuele Polino, Farzad Ghafari, Dominick J. Joch, Luis Villegas-Aguilar, Lynden K. Shalm, Varun B. Verma, Marcus Huber, and Nora Tischler
Quantum states encoded in the time-bin degree of freedom of photons represent a fundamental resource for quantum information protocols. Traditional methods for generating and measuring time-bin-encoded quantum states face severe challenges due to optical instabilities, complex setups, and timing resolution requirements. To circumvent these issues, we leverage an approach based on Hong-Ou-Mandel interference and we propose and demonstrate a robust and scalable protocol to generate and measure arbitrary high-dimensional time-bin quantum states. We experimentally implement the protocol in a photonic setup reaching high-fidelity quantum state tomographies of two- and three-dimensional quantum states encoded in time bins with short temporal separation. We also certify intrasystem polarization-time entanglement of single photons through a nonclassicality test. The demonstrated approach enables access to high-dimensional states and tasks that are practically inaccessible with standard schemes, thereby advancing fundamental quantum information science and opening applications in quantum communication.
Phys. Rev. Lett. 134, 180802 (2025)
Optical quantum information processing, Quantum communication, protocols & technology, Quantum engineering, Quantum information architectures & platforms, Quantum measurements, Quantum protocols, Quantum tomography, Quantum walks
Dynamical Formation of Regular Black Holes
Research article | Alternative gravity theories | 2025-05-06 06:00 EDT
Pablo Bueno, Pablo A. Cano, Robie A. Hennigar, and Ángel J. Murcia
Nonsingular black hole solutions are generically possible in modified theories of gravity in dimensions D ≥ 5.
Phys. Rev. Lett. 134, 181401 (2025)
Alternative gravity theories, Classical black holes, General relativity, Gravitation, Gravity in dimensions other than four, Singularities In general relativity
Superconducting Levitated Detector of Gravitational Waves
Research article | Astrophysical studies of gravity | 2025-05-06 06:00 EDT
Daniel Carney, Gerard Higgins, Giacomo Marocco, and Michael Wentzel
A magnetically levitated mass couples to gravity and can act as an effective gravitational wave detector. We show that a superconducting sphere levitated in a quadrupolar magnetic field, when excited by a gravitational wave, will produce magnetic field fluctuations that can be read out using a flux tunable microwave resonator. With a readout operating at the standard quantum limit, such a system could achieve broadband strain noise sensitivity of $h\lesssim {10}^{- 20}/\sqrt{\mathrm{Hz}}$ for frequencies of 1 kHz–1 MHz, opening new corridors for astrophysical probes of new physics.
Phys. Rev. Lett. 134, 181402 (2025)
Astrophysical studies of gravity, Gravitational wave detection, Gravitational waves
Class $\mathcal{S}$ Superconformal Indices from Maximal Supergravity
Compactification | 2025-05-06 06:00 EDT
Ritabrata Bhattacharya, Abhay Katyal, and Oscar Varela
We present a new gauging of maximal supergravity in five spacetime dimensions with gauge group containing ISO(5), involving the local scaling symmetry of the metric, and admitting a supersymmetric anti–de Sitter vacuum. We show this maximal supergravity to arise by consistent truncation of M theory on the (nonspherical, nonparallelizable) six-dimensional geometry associated to a stack of $N$ M5 branes wrapped on a smooth Riemann surface. The existence of this truncation allows us to holographically determine the complete, universal spectrum of light operators of the dual four-dimensional $\mathcal{N}=2$ theory of class $\mathcal{S}$. We then compute holographically the superconformal index of the dual field theory at large $N$, finding perfect agreement with previously known field theory results in specific limits.
Phys. Rev. Lett. 134, 181601 (2025)
Compactification, Conformal field theory, Gauge theories, Gauge-gravity dualities, Geometry, M-theory, String dualities, Supergravity, Supersymmetric field theories
Constraints on Axion Mediated Dipole-Dipole Interactions
Research article | Atomic & molecular processes in external fields | 2025-05-06 06:00 EDT
Zitong Xu, Xing Heng, Guoqing Tian, Di Gong, Lei Cong, Wei Ji, Dmitry Budker, and Kai Wei
The search for axions sits at the intersection of solving critical problems in fundamental physics, including the strong $CP$ problem in QCD, uncovering the nature of dark matter, and understanding the origin of the Universe’s matter-antimatter asymmetry. The measurement of axion mediated spin-dependent interactions offers a powerful approach for axion detection. However, it has long been restricted to regions outside the ‘’axion window’’ due to a significant trade-off: the need to effectively suppress the magnetic leakage from highly polarized spin sources while simultaneously detecting subfemtotesla level exotic physics signals at sub-decimeter-scale distances. In this work, we report new experimental results on axion mediated exotic spin-spin interactions using an iron-shielded ${\mathrm{SmCo}}_{5}$ spin source in combination with a specially designed self-compensation comagnetometer. Employing a composite shielding structure, we achieved a suppression of the magnetic field by up to ${10}^{11}$. This enabled us to establish new constraints on the coupling between electrons and neutrons, improving previous experimental limits by up to 10 000 times within the axion window. Furthermore, we also set the strongest constraints on the coupling between electrons and protons. The proposed method holds substantial potential not only for advancing the search for new physics beyond the standard model but also for enabling transformative applications in biological and chemical research.
Phys. Rev. Lett. 134, 181801 (2025)
Atomic & molecular processes in external fields, Axions, Baryogenesis & leptogenesis, Electro-optical spectra, Electronic transitions, Hierarchy problem, Light-matter interaction, Long-range interactions, Magnetic moment, Magneto-optical spectra, Magnetometry, Metrology, Nuclear & electron resonance, Optical pumping, Optical transient phenomena, Particle dark matter, Quantum control, Quantum metrology, Zeeman effect
Discovering Electroweak Interacting Dark Matter at Muon Colliders Using Soft Tracks
Research article | Particle dark matter | 2025-05-06 06:00 EDT
Rodolfo Capdevilla, Federico Meloni, and Jose Zurita
Minimal dark matter models feature one neutral particle that serves as a thermal relic dark matter candidate, as well as quasidegenerate charged states with TeV masses. When the charged states are produced at colliders, they can decay into dark matter and a low-momentum (soft) charged particle, which is challenging to reconstruct at hadron colliders. We demonstrate that a 3 TeV muon collider is capable of detecting these soft tracks, enabling the discovery of thermal Higgsinos and similar dark matter candidates that constitute highly motivated scenarios for future collider searches.
Phys. Rev. Lett. 134, 181802 (2025)
Particle dark matter, Phenomenology, Supersymmetric models, Muon accelerators & neutrino factories, Lepton colliders
Time-Resolved Spectral Gap Spectroscopy in a Quantum Simulator of Fermionic Superfluidity inside an Optical Cavity
Research article | Cavity quantum electrodynamics | 2025-05-06 06:00 EDT
Dylan J. Young, Eric Yilun Song, Anjun Chu, Diego Barberena, Zhijing Niu, Vera M. Schäfer, Robert J. Lewis-Swan, Ana Maria Rey, and James K. Thompson
We use an ensemble of laser-cooled strontium atoms in a high-finesse cavity to cleanly emulate the technique of rf spectroscopy employed in studies of BEC-BCS physics in fermionic superfluids of degenerate cold gases. Here, we leverage the multilevel internal structure of the atoms to study the physics of Cooper pair breaking in this system. In doing so, we observe and distinguish the properties of two distinct many-body gaps, the BCS pairing gap and the spectral gap, using nondestructive readout techniques. The latter is found to depend on the populations of the internal atomic states, reflecting the chemical potential dependence predicted in fermionic superfluids. This work opens the path for more fully exploiting the rich internal structure of atoms in cavity QED emulators to study both analogous systems and also more exotic states yet to be realized.
Phys. Rev. Lett. 134, 183404 (2025)
Cavity quantum electrodynamics, Quantum simulation, Atoms, Nonequilibrium systems, Superfluids
Self-Organized Cavity Bosons beyond the Adiabatic Elimination Approximation
Research article | Cavity quantum electrodynamics | 2025-05-06 06:00 EDT
Giuliano Orso, Jakub Zakrzewski, and Piotr Deuar
The longtime behavior of weakly interacting bosons moving in a two-dimensional optical lattice and coupled to a lossy cavity is investigated numerically via the truncated Wigner method, which allows us to take into full account the dynamics of the cavity mode, quantum fluctuations, cavity-boson correlations, and self-organization of individual runs. We first compare our results for small systems with quasi-exact calculations based on quantum trajectories, finding a remarkably good agreement for experimentally relevant boson fillings that improves further with system size. For large systems, we observe metastability at very long times and superfluid quasi–long range order, in sharp contrast with the true long range order found in the ground state of the approximate Bose-Hubbard model with extended interactions, obtained by adiabatically eliminating the cavity field. As the strength of the light-matter coupling increases, the system first becomes supersolid at the Dicke superradiant transition and then turns into a charge-density wave via the Berezinskii-Kosterlitz-Thouless mechanism. The two phase transitions are characterized via an accurate finite-size scaling analysis.
Phys. Rev. Lett. 134, 183405 (2025)
Cavity quantum electrodynamics, Collective effects in atomic physics, Dissipative dynamics, Bose gases, Supersolids, Full counting statistics
Plasmonic Time Crystals
Research article | Photonic crystals | 2025-05-06 06:00 EDT
Joshua Feinberg, David E. Fernandes, Boris Shapiro, and Mário G. Silveirinha
Photonic time-crystals when extended to plasmonic media can support collective resonance of longitudinal plasmons that can significantly enhance parametric gain.
Phys. Rev. Lett. 134, 183801 (2025)
Photonic crystals, Photonics, Plasmonics, Optical parametric oscillators & amplifiers
Nonmonotonic Motion of Sliding Droplets on Strained Soft Solids
Research article | Capillary interactions | 2025-05-06 06:00 EDT
Youchuang Chao, Hansol Jeon, and Stefan Karpitschka
Soft materials are ubiquitous in technological applications that require deformability, for instance, in flexible, water-repellent coatings. However, the wetting properties of prestrained soft materials are only beginning to be explored. Here we study the sliding dynamics of droplets on prestrained soft silicone gels, both in tension and in compression. Intriguingly, in compression we find a nonmonotonic strain dependence of the sliding speed: mild compressions decelerate the droplets, but stronger compressions lead again to faster droplet motion. Upon further compression, creases nucleate under the droplets until, finally, the entire surface undergoes the creasing instability, causing a ‘’run-and-stop’’ motion. We quantitatively elucidate the speed modification for moderate prestrains by incremental viscoelasticity, while the acceleration for larger prestrains turns out to be linked to the solid pressure, presumably through a lubrication effect of expelled oligomers.
Phys. Rev. Lett. 134, 184001 (2025)
Capillary interactions, Elastic deformation, Elastic forces, Friction, Internal friction, Osmotic interactions, Rheology, Strain, Wetting, Elastomers, Polymer gels, Microrheology, Strain engineering
Reduced Model of Ionization Lag in Intense Laser-Produced Plasmas
Research article | Direct drive | 2025-05-06 06:00 EDT
M. S. Cho, A. L. Milder, W. Rozmus, H. P. Le, H. A. Scott, D. T. Bishel, D. Turnbull, S. B. Libby, and M. E. Foord
A physics-based empirical formula is derived to predict the ionization lag in underdense plasmas generated by an intense laser. Time-dependent nonlocal thermodynamic equilibrium calculations demonstrate significantly delayed ionization, due to rapid changes in plasma conditions, which critically impacts plasma properties such as opacity, emissivity, and heat transport. The reduced model, based on these calculations, enables the estimation of ionization lag without requiring in-depth knowledge of nonlocal thermodynamic equilibrium modeling. Furthermore, modeling reveals that the two-step ionization process—collisional excitation followed by photoionization—plays a crucial role in this ionization delay, with collisional excitation setting the timescale for ionization. Simulations across a range of elements, from beryllium to germanium, demonstrate that ionization lag is a widespread phenomenon, underscoring the importance of incorporating such processes into ionization modeling in radiation hydrodynamic simulations for various laser-plasma experiments.
Phys. Rev. Lett. 134, 185101 (2025)
Direct drive, Laser-plasma interactions, Plasma ionization, Plasma transport, Plasma-beam interactions
Nonperturbative Self-Consistent Electron-Phonon Spectral Functions and Transport
Research article | Electron-phonon coupling | 2025-05-06 06:00 EDT
Jae-Mo Lihm and Samuel Poncé
Electron-phonon coupling often dominates the electron spectral functions and carrier transport properties. However, studies of this effect in real materials have largely relied on perturbative one-shot methods due to the lack of a first-principles theoretical and computational framework. Here, we present a self-consistent theory and implementation for the nonperturbative calculations of spectral functions and conductivity due to electron-phonon coupling. Applying this method to monolayer InSe, we demonstrate that self-consistency qualitatively affects the spectral function and transport properties compared to state-of-the-art one-shot calculations and allow one to reconcile calculations with angle-resolved photoemission experiments. The developed method can be widely applied to materials with dominant electron-phonon coupling at moderate computational cost.
Phys. Rev. Lett. 134, 186401 (2025)
Electron-phonon coupling, Transport phenomena, 2-dimensional systems, Angle-resolved photoemission spectroscopy, First-principles calculations
Anomalous Electrical Transport in the Kagome Magnet ${\mathrm{YbFe}}{6}{\mathrm{Ge}}{6}$
Research article | Magnetism | 2025-05-06 06:00 EDT
Weiliang Yao, Supeng Liu, Hodaka Kikuchi, Hajime Ishikawa, Øystein S. Fjellvåg, David W. Tam, Feng Ye, Douglas L. Abernathy, George D. A. Wood, Devashibhai Adroja, Chun-Ming Wu, Chien-Lung Huang, Bin Gao, Yaofeng Xie, Yuxiang Gao, Karthik Rao, Emilia Morosan, Koichi Kindo, Takatsugu Masuda, Kenichiro Hashimoto, Takasada Shibauchi, and Pengcheng Dai
Two-dimensional (2D) kagome metals offer a unique platform for exploring electron correlation phenomena derived from quantum many-body effects. Here, we report a combined study of electrical magnetotransport and neutron scattering on ${\mathrm{YbFe}}{6}{\mathrm{Ge}}{6}$, where the Fe moments in the 2D kagome layers exhibit an $A$-type collinear antiferromagnetic order below ${T}{\mathrm{N}}\approx 500\text{ }\text{ }\mathrm{K}$. Interactions between the Fe ions in the layers and the localized Yb magnetic ions in between reorient the $c$-axis-aligned Fe moments to the kagome plane below ${T}{\mathrm{SR}}\approx 63\text{ }\text{ }\mathrm{K}$. Our magnetotransport measurements show an intriguing anomalous Hall effect (AHE) that emerges in the spin-reorientated collinear state, accompanied by the closing of the spin anisotropy gap as revealed from inelastic neutron scattering. The gapless spin excitations and the Yb-Fe interaction are able to support a dynamic scalar spin chirality, which explains the observed AHE. Therefore, our Letter demonstrates that spin fluctuations may provide an additional scattering channel for the conduction electrons and give rise to AHE even in a collinear antiferromagnet.
Phys. Rev. Lett. 134, 186501 (2025)
Magnetism, Kagome metal, Magnetization measurements, Neutron scattering, Resistivity measurements
Non-Abelian Gauge Theory for Magnons in Topologically Textured Frustrated Magnets
Research article | Frustrated magnetism | 2025-05-06 06:00 EDT
Ricardo Zarzuela and Se Kwon Kim
We develop an effective gauge theory for three-flavored magnons in frustrated magnets hosting topological textures with the aid of the quaternion representation of the SO(3) order parameter. We find that the effect of topological solitons on magnons is captured generally by the non-Abelian emergent electromagnetic fields, distinct from the previously established gauge theory for magnons in collinear magnets where the gauge theory is often restricted to be Abelian. As concrete examples, $4\pi $ vortices in two- and three-dimensional magnets and Shankar skyrmions in three-dimensional magnets are discussed in detail, which are shown to induce, respectively, the Abelian and the non-Abelian topological magnetic field on magnons, and thereby engender the topological Hall transport in textured frustrated magnets. We also discuss the effect of magnon-magnon interactions on our effective theory. Our work is applicable to a broad class of magnetic materials whose low-energy manifold is described by the SO(3) order parameter. We envision that the discovery of the non-Abelian magnonic gauge theory will enrich the field of magnonics as well as prompt the study of magnon transport in textured frustrated magnets.
Phys. Rev. Lett. 134, 186701 (2025)
Frustrated magnetism, Hall effect, Magnetic texture, Non-Abelian gauge theories, Spintronics, Transport phenomena
Mass-Singularity-Induced Phase Jump in High-Harmonic Generation from Symmetry-Breaking Crystals
Research article | High-order harmonic generation | 2025-05-06 06:00 EDT
Jia-Xiang Chen and Xue-Bin Bian
Symmetry plays a central role in fundamental physics. Here we identify a phase-jump phenomenon in high-order harmonic generation in symmetry-breaking crystals. This phenomenon originates from the singularity in the effective mass of electron-hole pairs at nonzero-distance collisions, a factor usually ignored in the literature. However, it determines the basic properties of harmonic emissions. This phase-jump phenomenon results in a suppression of the harmonic spectrum by orders, which is strongly orientation dependent. It is universal and not limited to a specific crystal. Clues to this can be found in published ab initio simulations and experimental results, but not interpreted. Our findings pave the way for a better understanding of the ultrafast dynamics of electron-hole pairs in XUV photon emission.
Phys. Rev. Lett. 134, 186901 (2025)
High-order harmonic generation, Ultrafast optics
Geometric Control and Memory in Networks of Hysteretic Elements
Research article | Elastic deformation | 2025-05-06 06:00 EDT
Dor Shohat and Martin van Hecke
The response of driven frustrated media stems from interacting hysteretic elements. We derive explicit mappings from networks of hysteretic springs to their abstract representation as interacting hysterons. These mappings reveal how the physical network controls the signs, magnitudes, symmetries, and pairwise nature of the hysteron interactions. In addition, strong geometric nonlinearities can produce pathways that require excess hysterons or even break hysteron models. Our results pave the way for metamaterials with geometrically controlled interactions, pathways, and functionalities, and highlight fundamental limitations of abstract hysterons in modeling disordered systems.
Phys. Rev. Lett. 134, 188201 (2025)
Elastic deformation, Mechanical metamaterials, Smart materials
Activity Leads to Topological Phase Transition in 2D Populations of Heterogeneous Oscillators
Research article | Active defects | 2025-05-06 06:00 EDT
Ylann Rouzaire, Parisa Rahmani, Ignacio Pagonabarraga, Fernando Peruani, and Demian Levis
Populations of heterogeneous, noisy oscillators on a two-dimensional lattice display short-range order. Here, we show that if the oscillators are allowed to actively move in space, the system undergoes instead a Berezenskii-Kosterlitz-Thouless transition and exhibits quasi-long-range order. This fundamental result connects two paradigmatic models—the XY and Kuramoto models—and provides insight into the emergence of order in active systems.
Phys. Rev. Lett. 134, 188301 (2025)
Active defects, Classical spin models, Collective dynamics, Dry active matter, Living matter & active matter, Kuramoto model, Langevin equation, Theories of collective dynamics & active matter, XY model
Physical Review X
Topological Meron-Antimeron Domain Walls and Skyrmions in a Low-Symmetry System
Research article | Domain walls | 2025-05-06 06:00 EDT
Reiner Brüning, Levente Rózsa, Roberto Lo Conte, André Kubetzka, Roland Wiesendanger, and Kirsten von Bergmann
A low-symmetry system–realized in an iron layer on a tantalum substrate–shows unique topological magnetic domain walls. Nontrivial structures in these walls respond asymmetrically to magnetic fields, enabling the creation of skyrmion chains.
Phys. Rev. X 15, 021041 (2025)
Domain walls, Magnetic coupling, Magnetic texture, Magnetic vortices, Skyrmions, Spintronics, Magnetic thin films, Density functional theory, Scanning tunneling microscopy
Theoretical Lower Limit of Coercive Field in Ferroelectric Hafnia
Research article | Domain wall motion | 2025-05-06 06:00 EDT
Jiyuan Yang, Jing Wu, Jingxuan Li, Chao Zhou, Yang Sun, Zuhuang Chen, and Shi Liu
Polarization switching in ultrathin hafnia films requires very high electric fields, limiting its use in next-generation nanoelectronics. A new type of domain-wall-driven switching in thicker films lowers those switching fields.
Phys. Rev. X 15, 021042 (2025)
Domain wall motion, Ferroelectric domains, Ferroelectricity, Nucleation, Electronically polarized systems, Density functional theory, Molecular dynamics
arXiv
Doping lattice non-abelian quantum Hall states
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-05-07 20:00 EDT
Zhengyan Darius Shi, Carolyn Zhang, T. Senthil
We study quantum phases of a fluid of mobile charged non-abelian anyons, which arise upon doping the lattice Moore-Read quantum Hall state at lattice filling $ \nu = 1/2$ and its generalizations to the Read-Rezayi ($ \mathrm{RR}_k$ ) sequence at $ \nu = k/(k+2)$ . In contrast to their abelian counterparts, non-abelian anyons present unique challenges due to their non-invertible fusion rules and non-abelian braiding structures. We address these challenges using a Chern-Simons-Ginzburg-Landau (CSGL) framework that incorporates the crucial effect of energy splitting between different anyon fusion channels at nonzero dopant density. For the Moore-Read state, we show that doping the charge $ e/4$ non-abelion naturally leads to a fully gapped charge-$ 2$ superconductor without any coexisting topological order. The chiral central charge of the superconductor depends on details of the interactions determining the splitting of anyon fusion channels. For general $ \mathrm{RR}_k$ states, our analysis of states obtained by doping the basic non-abelion $ a_0$ with charge $ e/(k+2)$ reveals a striking even/odd pattern in the Read-Rezayi index $ k$ . We develop a general physical picture for anyon-driven superconductivity based on charge-flux unbinding, and show how it relates to the CSGL description of doped abelian quantum Hall states. Finally, as a bonus, we use the CSGL formalism to describe transitions between the $ \mathrm{RR}_k$ state and a trivial period-$ (k+2)$ CDW insulator at fixed filling, driven by the gap closure of the fundamental non-abelian anyon $ a_0$ . Notably, for $ k=2$ , this predicts a period-4 CDW neighboring the Moore-Read state at half-filling, offering a potential explanation of recent numerical observations in models of twisted MoTe$ _2$ .
Strongly Correlated Electrons (cond-mat.str-el), Superconductivity (cond-mat.supr-con), High Energy Physics - Theory (hep-th)
32 pages, 2 figures, 14 pages of appendices
Upper bound on $T_c$ in a strongly coupled electron-boson superconductor
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-05-07 20:00 EDT
Nikolay V. Gnezdilov, Rufus Boyack
Migdal-Eliashberg theory (METh) of boson-mediated superconductivity contains a $ \sqrt{\lambda}$ divergence in the critical temperature $ T_c$ at strong electron-boson coupling $ \lambda$ . In conventional METh, the strong-coupling regime can be accessed only in the limit that $ \lambda_E = \lambda , \omega_D/\varepsilon_F\ll1$ , where $ \omega_D$ is the Debye frequency and $ \varepsilon_F$ is the Fermi energy. Here we go beyond this restriction in the context of the two-dimensional Yukawa-SYK (Y-SYK) model, which is solvable for arbitrary values of $ \lambda_E$ . We find that $ T_c\approx 0.18 ,\omega_D \sqrt{\lambda}$ for large $ \lambda$ , provided $ \lambda_E$ remains small, and crosses over to a universal value of $ T_c \approx 0.04, \varepsilon_F$ for large $ \lambda_E$ . The saturation of $ T_c$ is due to a self-consistent account of the boson dynamics for large $ \lambda_E$ and is arguably qualitatively valid beyond the Y-SYK framework. These results demonstrate how the $ \sqrt{\lambda}$ growth of $ T_c$ in METh saturates to a universal value independent of $ \lambda$ and $ \omega_D$ , providing an upper bound on the critical temperature at strong electron-boson coupling.
Strongly Correlated Electrons (cond-mat.str-el), Superconductivity (cond-mat.supr-con)
7 pages, 1 figure; supplemental material: 5 pages, 3 figures
XDiag: Exact Diagonalization for quantum many-body systems
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-05-07 20:00 EDT
Alexander Wietek, Luke Staszewski, Martin Ulaga, Paul L. Ebert, Hannes Karlsson, Siddhartha Sarkar, Henry Shackleton, Aritra Sinha, Rafael D. Soares
Exact diagonalization (ED) is a cornerstone technique in quantum many-body physics, enabling precise solutions to the Schrödinger equation for interacting quantum systems. Despite its utility in studying ground states, excited states, and dynamical behaviors, the exponential growth of the Hilbert space with system size presents significant computational challenges. We introduce XDiag, an open-source software package designed to combine advanced and efficient algorithms for ED with and without symmetry-adapted bases with user-friendly interfaces. Implemented in C++ for computational efficiency and wrapped in Julia for ease of use, XDiag provides a comprehensive toolkit for ED calculations. Key features of XDiag include the first publicly accessible implementation of sublattice coding algorithms for large-scale spin system diagonalizations, efficient Lin table algorithms for symmetry lookups, and random-hashing techniques for distributed memory parallelization. The library supports various Hilbert space types (e.g., spin-1/2, electron, and t-J models), facilitates symmetry-adapted block calculations, and automates symmetry considerations. The package is complemented by extensive documentation, a user guide, reproducible benchmarks demonstrating near-linear scaling on thousands of CPU cores, and over 20 examples covering ground-state calculations, spectral functions, time evolution, and thermal states. By integrating high-performance computing with accessible scripting capabilities, XDiag allows researchers to perform state-of-the-art ED simulations and explore quantum many-body phenomena with unprecedented flexibility and efficiency.
Strongly Correlated Electrons (cond-mat.str-el), Computational Physics (physics.comp-ph)
29 pages, 4 figures
Chiral Gravitons on the Lattice
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-05-07 20:00 EDT
Hernan B. Xavier, Zeno Bacciconi, Titas Chanda, Dam Thanh Son, Marcello Dalmonte
Chiral graviton modes are elusive excitations arising from the hidden quantum geometry of fractional quantum Hall states. It remains unclear, however, whether this picture extends to lattice models, where continuum translations are broken and additional quasiparticle decay channels arise. We present a framework in which we explicitly derive a field theory incorporating lattice chiral graviton operators within the paradigmatic bosonic Harper-Hofstadter model. Extensive numerical evidence suggests that chiral graviton modes persist away from the continuum, and are well captured by the proposed lattice operators. We identify geometric quenches as a viable experimental probe, paving the way for the exploration of chiral gravitons in near-term quantum simulation experiments.
Strongly Correlated Electrons (cond-mat.str-el), Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Quantum Gases (cond-mat.quant-gas)
7+5 pages, 4+4 figures
Quantum geometry and dipolar dynamics in the orbital magneto-electric effect
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-05-07 20:00 EDT
James H. Cullen, Daniel P. Arovas, Roberto Raimondi, Dimitrie Culcer
We show that the orbital magneto-electric effect (OME) – the generation of a steady-state orbital angular momentum density – is partly the result of a nonequilibrium dipole moment generated via Zitterbewegung and proportional to the quantum metric. For tilted massive Dirac fermions this dipole gives the only contribution to the OME in the insulating case, while the intrinsic and extrinsic OMEs occur for different electric field orientations, yielding an experimental detection method. Our results suggest quantum metric engineering as a route towards maximizing orbital torques.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
The Physics of Local Optimization in Complex Disordered Systems
New Submission | Disordered Systems and Neural Networks (cond-mat.dis-nn) | 2025-05-07 20:00 EDT
Mutian Shen, Gerardo Ortiz, Zhiqiao Dong, Martin Weigel, Zohar Nussinov
Limited resources motivate decomposing large-scale problems into smaller, “local” subsystems and stitching together the so-found solutions. We explore the physics underlying this approach and discuss the concept of “local hardness”, i.e., complexity from the local solver perspective, in determining the ground states of both P- and NP-hard spin-glasses and related systems. Depending on the model considered, we observe varying scaling behaviors in how errors associated with local predictions decay as a function of the size of the solved subsystem. These errors stem from global critical threshold instabilities, characterized by gapless, avalanche-like excitations that follow scale-invariant size distributions. Away from criticality, local solvers quickly achieve high accuracy, aligning closely with the results of the more computationally intensive global minimization. These findings shed light on how Nature may operate solely through local actions at her disposal.
Disordered Systems and Neural Networks (cond-mat.dis-nn), Statistical Mechanics (cond-mat.stat-mech), Computational Physics (physics.comp-ph)
21 pages, 22 figures
Electronic structure and exchange interactions in altermagnetic MnGeP$_2$ in the quasiparticle-self-consistent $GW$ approach
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-05-07 20:00 EDT
Ilteris K. Turan, Walter R L. Lambrecht, Jerome Jackson
The QS$ GW$ method is used to study the electronic band structure, optical dielectric function, and exchange interactions in chalcopyrite, $ I\bar{4}2d$ , structure MnGeP$ _2$ . The material is found to be an antiferromagnetic semiconductor with lowest direct gap of 2.44 eV at the $ \Gamma$ point and an indirect gap of 2.16 eV. The spin splittings along a low symmetry line like $ PN$ are sizable, while at {\bf k}-points on the diagonal mirror planes or on the twofold symmetry axes the spin splitting is zero. The exchange interactions are calculated using a linear response approach. The antiferromagnetic exchange-interaction between nearest neighbors in the primitive unit cell is dominating and found to be slightly decreasing upon carrier doping. The transverse spin susceptibilities, which provide interatomic site exchange interactions after averaging over the muffin-tin spheres, are calculated from the $ GW$ band structure and wave functions. From these exchange interactions, the spin wave spectra are obtained along the high symmetry lines and the Néel temperature is calculated using the mean-field, and Tyablikov estimations. The dielectric function and the optical absorption spectra are calculated including excitonic effects using the Bethe Salpeter equation. The exchange interactions around Mn$ _{\rm Ge}$ defect sites is also studied. While we find it can generate ferromagnetic interactions with neighboring spins, we did not find evidence of producing an overall ferromagnetic phase. If Mn antisites are introduced by exchanging Mn with a nearby Ge, the interactions stay largely antiferromagnetic. Adding Mn antisites leads to a metallic band structure.
Materials Science (cond-mat.mtrl-sci)
13 pages, 9 figures
Doping-induced Spin Reorientation in Kagome Magnet TmMn6Sn6
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-05-07 20:00 EDT
Mohamed El Gazzah, Po-Hao Chang, Y. Lee, Hari Bhandari, Resham Regmi, Xiuqan Zhou, John F. Mitchell, Liqin Ke, Igor I. Mazin, Nirmal J. Ghimire
The kagome-lattice compounds RMn6Sn6 (R is a rare earth element), where the Mn atoms form a kagome net in the basal plane, are currently attracting a great deal of attention as they have been shown to host complex magnetic textures and electronic topological states strongly sensitive to the choice of the R atom. Among the magnetic R atoms, TmMn6Sn6 orders with the easy-plane magnetization forming a complex magnetic spiral along the c-axis. Previous neutron studies, carried on polycrystalline, samples found that Ga doping changes the magnetic anisotropy from easy-plane to easy-axis. Here we present magnetic and magnetotransport measurements on a single crystal and first principles calculations in the doping series of TmMn6Sn6-xGax. We find that the magnetic properties are highly sensitive even to a small concentration of Ga. With minimal Ga substitution, the easy-plane anisotropy is maintained, which gradually changes to the easy-axis anisotropy with increasing Ga. We discuss these observations with respect to the effect of Ga doping on magnetocrystalline anisotropy and Tm crystal field
Materials Science (cond-mat.mtrl-sci)
Multi-channel second-order topological states in 3D Dirac semimetal Bi${0.97}$Sb${0.03}$
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-05-07 20:00 EDT
Biplab Bhattacharyya, Stijn R. de Wit, Zhen Wu, Yingkai Huang, Mark S. Golden, Alexander Brinkman, Chuan Li
Second-order topological insulating (SOTI) states in three-dimensional materials are helical dissipation-less one-dimensional (1D) hinges, which are of great interest for fundamental physics and potential topological quantum computing. Here, we report the discovery of SOTI states in Bi$ _{0.97}$ Sb$ _{0.03}$ nano-flakes by tuning junction length, flake thickness, and temperature. We identify signatures of higher-order topology from a strong correlation between the fractional Shapiro step, a signature of 4$ \pi$ -periodic supercurrent, and the presence of the hinge states. Tight-binding simulations confirm the presence of multiple hinge modes, supporting our interpretation of Bi$ _{0.97}$ Sb$ _{0.03}$ as a prototypical SOTI platform with tunable superconducting properties.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Superconductivity (cond-mat.supr-con)
Probing Vortex Dynamics in 2D Superconductors with Scanning Quantum Microscope
New Submission | Superconductivity (cond-mat.supr-con) | 2025-05-07 20:00 EDT
Sreehari Jayaram, Malik Lenger, Dong Zhao, Lucas Pupim, Takashi Taniguchi, Kenji Watanabe, Ruoming Peng, Marc Scheffler, Rainer Stöhr, Mathias S. Scheurer, Jurgen Smet, Jörg Wrachtrup
The visualization of the magnetic responses of a two-dimensional (2D) superconducting material on the nanoscale is a powerful approach to unravel the underlying supercurrent behavior and to investigate critical phenomena in reduced dimensions. In this study, scanning quantum microscopy is utilized to explore the local magnetic response of the 2D superconductor 2H-NbSe2. Our technique enables both static and dynamic sensing of superconducting vortices with high sensitivity and a spatial resolution down to 30 nm, unveiling unexpected phenomena linked to the intrinsic 2D nature of the superconductor, which are challenging to detect with more conventional local probes. Vortices do not arrange in a hexagonal lattice, but form a distorted vortex glass with expanding vortex size. A vortex can exhibit strong local dynamics due to thermal excitation. As the critical temperature is approached, a clear melting of the vortex glass is identified, leading to distinct configurations under different cooling conditions. Vortex fluctuations can also be probed through spin Hahn-echo measurements, which reveal the spin decoherence even well below the critical temperature – and, intriguingly, enhanced decoherence at lower temperatures. Spatiotemporal microscopy of the magnetic dynamics associated with vortex excitations and fluctuations provides direct evidence of 2D superconducting phenomena at the nanoscale.
Superconductivity (cond-mat.supr-con), Materials Science (cond-mat.mtrl-sci), Quantum Physics (quant-ph)
Ferroelectric Nematic and Smectic Liquid Crystals with Sub-Molecular Spatial Correlations
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-05-07 20:00 EDT
Parikshit Guragain, Arjun Ghimire, Manisha Badu, Netra Prasad Dhakal, Pawan Nepal, James T. Gleeson, Samuel Sprunt, Robert J. Twieg, Antal Jákli
A number of highly polar three ring rod-shaped compounds with a terminal thiophene ring have been synthesized and the physical properties of a subset are reported in detail. On cooling from the isotropic fluid, they directly transition to a ferroelectric nematic liquid crystal (NF) phase that shows the strongest spatial correlations corresponding to 1/3 of the molecular length (L/3). The set of thiophene compounds reported here have ferroelectric polarizations about 20% larger than that of usual ferroelectric nematic liquid crystal materials. Such large polarization values are due to the ~20% larger mass densities of these thiophene compounds compared to most of the NF materials with short terminal chains. These unusual properties are consequences of tighter molecular packing due to the lack of flexible terminal chains. Below the NF phase, compounds with a single nitro or two cyano polar groups on the terminal benzene ring exhibit a so far never observed smectic phase with periodicity ~1/3 the molecular length. Based on our experimental results, we propose a model of this phase featuring antipolar packing of the molecules within the layers.
Soft Condensed Matter (cond-mat.soft), Materials Science (cond-mat.mtrl-sci)
53 pages, 43 figures
Interplay of quantum and real-space geometry in the anomalous Landau levels of singular flat bands
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-05-07 20:00 EDT
Quantum geometry of electronic state in momentum space, distinct from real-space structural geometry, has attracted increasing interest to shed light on understanding quantum phenomena. An interesting recent study [Nature 584, 59-63 (2020)] has numerically solved a 2-band effective Hamiltonian to show the anomalous Landau level (ALL) spreading $ \mathit{\Delta}$ of a singular flat band (SFB), such as hosted in a kagome lattice, in relation to the maximal quantum distance $ d$ of the SFB, $ \mathit{\Delta}(d)$ , which enables a direct measure of quantum geometry. Here, we investigate the ALLs of SFB by studying both the 2-band Hamiltonian and a diatomic kagome lattice hosting two SFBs mirrored by particle-hole symmetry. We derive an exact analytical solution of the 2-band Hamiltonian to show there are two branches of $ \mathit{\Delta}(d)$ . Strikingly, for the diatomic kagome lattice, $ \mathit{\Delta}$ depends on not only $ d$ but also $ r$ , the real-space diatomic distance. As $ r$ increases, $ \mathit{\Delta}$ shrinks toward zero while $ d$ remains intact, which can be intuitively understood from the magnetic-field-induced disruption of destructive interference of the SFB compact localized states. Based on semiclassical theory, we derive rigorously the dependence of $ \mathit{\Delta}$ on $ r$ that originates from the tuning of the non-Abelian orbital moment of the two SFBs by real-space geometry.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Neighbor-induced damage percolation
New Submission | Disordered Systems and Neural Networks (cond-mat.dis-nn) | 2025-05-07 20:00 EDT
Lorenzo Cirigliano, Claudio Castellano
We consider neighbor-induced damage percolation, a model describing systems where the inactivation of some elements may damage their neighboring active ones, making them unusable. We present an exact solution for the size of the giant usable component (GUC) and the giant damaged component (GDC) in uncorrelated random graphs. We show that, even for strongly heterogeneous distributions, the GUC always appears at a finite threshold and its formation is characterized by homogeneous mean-field percolation critical exponents. The threshold is a nonmonotonic function of connectivity: robustness is maximized by networks with finite optimal average degree. We also show that, if the average degree is large enough, a damaged phase appears, characterized by the existence of a GDC, bounded by two distinct percolation transitions. The birth and the dismantling of the GDC are characterized by standard percolation critical exponents in networks, except for the dismantling in scale-free networks where new critical exponents are found. Numerical simulations on regular lattices in D = 2 show that the existence of a GDC depends not only on the spatial dimension but also on the lattice coordination number.
Disordered Systems and Neural Networks (cond-mat.dis-nn), Statistical Mechanics (cond-mat.stat-mech)
8 pages, 7 figures + supplemental material
Atom-by-atom Imaging of Moiré Phasons using Electron Ptychography
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-05-07 20:00 EDT
Yichao Zhang, Ballal Ahammed, Sang Hyun Bae, Chia-Hao Lee, Jeffrey Huang, Mohammad Abir Hossain, Tawfiqur Rakib, Arend van der Zande, Elif Ertekin, Pinshane Y. Huang
Twisted 2D materials exhibit unique vibrational modes called moiré phonons, which arise from the moiré superlattice. Here, we demonstrate atom-by-atom imaging of phasons, an ultrasoft class of moiré phonons in twisted bilayer WSe2. Using ultrahigh-resolution (<15 pm) electron ptychography, we image the size and shape of each atom to extract time-averaged vibrational amplitudes as a function of twist angle and position. We observe several signature properties of moiré phasons, such as increased vibrational amplitudes at solitons and AA-stacked regions. By correlating experiments with molecular dynamics simulations and lattice dynamics calculations, we show phasons dominate the thermal vibrations in low-angle twisted bilayers. These results represent a powerful route to image thermal vibrations at atomic resolution, unlocking experimental studies of a thus-far hidden branch of moiré phonon physics.
Materials Science (cond-mat.mtrl-sci)
Proper Orthogonal Decomposition of a Superfluid Turbulent Wake
New Submission | Quantum Gases (cond-mat.quant-gas) | 2025-05-07 20:00 EDT
Sota Yoneda, Hiromitsu Takeuchi
Superfluid turbulent wakes behind a square prism are studied theoretically and numerically by proper orthogonal decomposition (POD). POD is a data science approach that can efficiently extract the principal vibration modes of a physical system, and is widely used in hydrodynamics, including applications in wake structure analysis. It is not straightforward to apply the conventional POD method to superfluid wake systems, as the superfluid velocity field diverges at the center of a vortex whose circulation is quantized. We successfully established a POD method by applying appropriate blurring to the vorticity distribution in a two-dimensional superfluid wake. It is shown that a coherent structure corresponding to two parallel arrays of alternating quantum vortex bundles, called the “quasi-classical” Kármán vortex street, is latent as a distinctive major mode in the superfluid turbulent wakes that were naively thought to be “irregular”. Since our method is also effective for fluid density, it can be applied to the experimental data analysis for ultra-cold atomic gases.
Quantum Gases (cond-mat.quant-gas)
Movies showing the time evolution of the wake presented in the main text is available from this https URL
Analytic Expressions for Most $f^n$ Valence Multiplet Eigenvalues
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-05-07 20:00 EDT
It is well know that many full atomic multiplet codes are available for experimentalists to check x-ray absorption or emission spectra against known valence materials to identify effect valence configuration of transition metal ions as well as their ligands. This has grown recently with the continued development of resonant inelastic x-ray scattering as a general tool that can characterize orbital, spin, charge, and lattice excitations in quantum materials. In this note, I show that all multiplet eigenstates for most $ f^n$ configurations can be obtained analytically. I correct prior misprints in the literature and present new results for $ f$ -electrons. These results can serve as checks against new and developed numerical codes, and further provide experimentalists with deeper insights into the many configurations probed by advanced x-ray spectroscopies.
Strongly Correlated Electrons (cond-mat.str-el), Materials Science (cond-mat.mtrl-sci), Mathematical Physics (math-ph)
Enhancing Contrast and Resolution for Electron-beam Lithography on Insulating Substrates
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-05-07 20:00 EDT
Deepak Kumar, Cooper Meyers, RJ Smith, J. Todd Hastings
We report on the effect of ambient gas on the contrast and the resolution of electron beam lithography (EBL) in gaseous environments on insulating substrates. Poly(methyl methacrylate) (PMMA) films were exposed in an environmental scanning electron microscope using a 30 keV electron-beam under 1 mbar pressure of helium, water, nitrogen and argon. We found that the choice of ambient gas results in significant variations in contrast, and the clearing dose increases with the gases molecular weight and proton number, consistent with the increase in scattering cross-section. Significantly higher contrast values are obtained for exposure under helium and are accompanied by improved sensitivity. Despite higher sensitivity, helium exhibited the best resolution with 20-nm half-pitch dense lines and spaces. However, water vapor offered a larger process window, particularly on fused silica substrates. We also demonstrate that higher sensitivity results from effective charge dissipation. Thus, for EBL on insulating substrates, helium and water vapor may be desirable choices for charge dissipation depending on the substrate and process conditions.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
12 pages, 6 figures
The unidirectional Seebeck detection of the Néel vector in the two-dimensional tetragonal $\mathcal{PT}$-symmetric antiferromagnetic materials
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-05-07 20:00 EDT
Ya-Ting Xiao, Ying-Li Wu, Jia-Liang Wan, Xiao-Qin Yu
The efficient detection of the reversal (180$ ^{\circ}$ rotation) of the Néel vector is one of the crucial tasks in antiferromagnetic spintronics. Here, we propose a thermal approach to detect the reversal of the Néel vector in the tetragonal $ \mathcal{PT}$ antiferromagnetic materials through the unidirectional Seebeck effect (USE). Being different from the previous works in which USE stems from the global Rashba spin-orbit coupling (SOC) or asymmetric magnon scattering, we find that the USE originates from the coupling of the hidden Rashba SOC and the Néel vector in the tetragonal $ \mathcal{PT}$ antiferromagnetic materials in the absence of the global Rashba SOC. Using a generic minimal model, we analyse the behaviors of the USE for the two-dimensional tetragonal lattice $ \mathcal{PT}$ antiferromagnet. Importantly, It’s found that when the Néel vector is reversed, the sign of the USE changes, which can be utilized to detect the reversal of the Néel vector.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
9 pages, 2 figures,Accepted by PRB
Finite-temperature properties of the prototypical perovskite CaTiO$_3$ from second-principles effective interatomic potential
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-05-07 20:00 EDT
Huazhang Zhang, Michael Marcus Schmitt, Louis Bastogne, Xu He, Philippe Ghosez
We introduce a second-principles effective interatomic potential for the perovskite $ \rm CaTiO_3$ (CTO), relying on a Taylor polynomial expansion of the Born-Oppenheimer energy surface around the cubic reference structure, in terms of atomic displacements and macroscopic strains. This model captures various phases of CTO, in particular successfully reproducing the structure, energy, and dynamical properties of the nonpolar $ Pbnm$ ground state as well as the ferroelectric $ R3c$ phase. The finite-temperature simulations suggest that the sequence of structural phase transitions over heating of CTO is: $ Pbnm \ (a^-a^-c^+) \rightarrow C2/m \ (a^-b^-c^0) \rightarrow I4/mcm \ (a^-c^0c^0) \rightarrow Pm\bar{3}m \ (a^0a^0a^0)$ , during which the oxygen octahedral rotations around the three pseudocubic axes vanish progressively. The model also provides the opportunity of investigating the properties of the ferroelectric $ R3c$ phase, which is a metastable phase free of lattice instability at zero Kelvin. Our model-based simulations confirm that the $ R3c$ phase remains stable below a certain finite temperature. Additionally, we find that the minimum energy path connecting the $ Pbnm$ and $ R3c$ phases involves localized layer-by-layer flipping of octahedral rotations. A similar mechanism is also observed in the thermal destabilization process of the $ R3c$ phase toward the $ Pbnm$ ground state in our simulation.
Materials Science (cond-mat.mtrl-sci)
Ultrafast dynamics of atomic correlated disordering in photoinduced VO$_2$
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-05-07 20:00 EDT
Wen-Hao Liu, Feng-Wu Guo, Lin-Wang Wang, Jun-Wei Luo
Recent experiments suggest that atomic disordering dynamics are more universal than conventional coherent processes in photoinduced phase transitions (PIPTs), yet its mechanism remains unclear. Using real-time time-dependent density functional theory (rt-TDDFT), we find that, at lower photoexcitation, higher lattice temperature accelerates atomic disordering, which thereby lowers the threshold for phase transition, by thermally exciting more phonons to randomize the lattice vibrations in VO$ _2$ . Above this threshold, however, we observe that the transition timescale and atomic disordering become temperature-independent since thermally excited lattice vibrations induce a similar evolution of photoexcited holes. Additionally, we show that photoexcitation initially elongates the V-V dimers followed by a rotation with tangential displacements (along the z-axis) mediated by O atoms, resulting in strongly correlated motion along the z-axis. Consequently, atomic disordering is more dominant along the x direction, attributed to the relatively unrestricted motion of V-V dimers along this direction. The motion of V atoms along the z-axis is more constrained, leading to less disorder along the z-axis, which results in a “correlated disorder” phenomenon. This anisotropic disordering in VO$ _2$ offers new insights into PIPTs mechanisms, guiding future studies on photoinduced disordered transitions.
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Computational Physics (physics.comp-ph)
27 pages, 18 figures
Scaling of Quantum Geometry Near the Non-Hermitian Topological Phase Transitions
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-05-07 20:00 EDT
Y R Kartik, Jhih-Shih You, H. H. Jen
The geometry of quantum states can be an indicator of criticality, yet it remains less explored under non-Hermitian topological conditions. In this work, we unveil diverse scalings of the quantum geometry over the ground state manifold close to different topological phase transitions in a non-Hermitian long-range extension of the Kitaev chain. The derivative of the geometric phase, as well as its scaling behavior, shows that systems with different long-range couplings can belong to distinct universality classes. Near certain criticalities, we further find that the Wannier state correlation function associated with extended Berry connection of the ground state exhibits spatially anomalous behaviors. Finally, we analyze the scaling of the quantum geometric tensor near phase transitions across exceptional points, shedding light on the emergence of novel universality classes.
Strongly Correlated Electrons (cond-mat.str-el), Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Statistical Mechanics (cond-mat.stat-mech), Quantum Physics (quant-ph)
6+4 pages, 4+1 figures, Comments and suggestions are welcome
Enhanced Patterned Fluorescence from Polystyrene through Focused Electron Beam Irradiation under Various Gases
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-05-07 20:00 EDT
Deepak Kumar, Joseph W. Brill, J. Todd Hastings
We report on a novel method for tuning and enhancing fluorescence from irradiated polystyrene through electron-beam exposure in gaseous environments. We describe the effect of electron dose and ambient gas on the photoluminescence spectra and yield of irradiated PS films on insulating and conductive substrates. PS films were exposed in an environmental scanning electron microscope using a 20 keV electron beam, ambient gas pressures from high vacuum to 3 mbar, and electron doses from 1.8 to 45 mC cm-2. Irradiated PS films were characterized using confocal microscopy, TEM, EDS and FTIR spectroscopy. From emission spectra collected using confocal microscopy we found that the emission wavelength and photon yield of the irradiated film can be tuned by both dose and gas pressure. The emission wavelength blue-shifts with increasing pressure and red-shifts with increasing dose enabling an overall tuning range of 451 - 544 nm. Significant enhancement in the PL intensity, up to 18 times on sapphire substrates under helium when compared to high vacuum, are observed. Overall, the highest PL yield is observed on soda lime glass substrates under argon. Also, the photon-yield on conductive substrates is significantly smaller than that yield from insulating substrates. TEM images revealed e-beam irradiated PS is amorphous in nature and elemental mapping EDS revealed no signs of film oxidation. FTIR spectroscopy revealed that under gaseous environments the decay of aromatic and aliphatic C-H stretches is reduced compared to the high vacuum exposure; in all cases, features associated with the phenyl rings are preserved. Localized e-beam synthesis of fluorophores in PS can be controlled by both dose and by ambient gas pressure. This technique could enable new approaches to photonics where fluorophores with tunable emission properties can be locally introduced by e-beam patterning.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
18 pages, 30 figures (including sub-figures)
Computational Analysis of Interface-Driven Spin-Orbit Coupling in Molecular Adsorbates on Transition Metal Dichalcogenides
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-05-07 20:00 EDT
Zihao Wang, Wan-Lu Li, Shaowei Li
Spin-orbit coupling (SOC) lifts molecular orbital degeneracy, enabling bi-level electronic platforms suitable for next-generation digital devices. However, common light-atom molecular feedstocks exhibit weak SOC due to the absence of heavy elements. To enhance SOC without synthesizing new materials, we leverage interfacial interactions between molecules and transition-element-based solid-state materials. This computational study investigates SOC splitting in metal-phthalocyanine adsorbed on transition metal dichalcogenides (TMDs) using density functional theory (DFT). The enhanced SOC splitting is attributed to strong orbital hybridization at the molecule-substrate interface. Specifically, Zn-phthalocyanine (ZnPC) on monolayer MoS2 achieves a notable SOC splitting of ~8 meV. Furthermore, when ZnPC forms self-assembled chains on MoS2, the splitting increases to ~20 meV, driven by the formation of hybrid bands modulated by molecular periodicity. These findings highlight the role of interfacial and intermolecular interactions in inducing and enhancing SOC in surface-adsorbed molecules, providing a new strategy for molecular spintronic materials without complex synthetic efforts.
Materials Science (cond-mat.mtrl-sci), Chemical Physics (physics.chem-ph), Computational Physics (physics.comp-ph)
6 pages, 4 figures
Mitigating parasitic contributions in measured piezoresponse for accurate determination of piezoelectric coefficients in Sc-alloyed-AlN thin films using piezo-response force microscopy
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-05-07 20:00 EDT
Ch Kishan Singh, K. Rajalakshmi, N. Balamurugan, Rakesh kumar, Mukul Gupta, R. Ramaseshan, Kiran Baraik
We present a methodology to mitigate the effect of the parasitic electrostatic contribution usually present in piezoresponse force microscopy (PFM) measurement for quantitative characterization of polycrystalline piezoelectric thin films using a case study on a set of Al1-xScxN thin films. It involves minimizing the voltage sensitivity of the measured piezoresponse by optimizing the optical lever sensitivity using the laser positioning of the beam-bounce system. Additionally, applying a dc-voltage offset (determined through Kelvin probe force microscopy) during PFM scans and positioning the probe over the interior or edge portion of the specimen are explored to minimize the local and non-local electrostatic tip-sample interaction. The results shows that the effective piezoelectric coefficient (d33-eff) of our c-axis oriented wurtzite (wz)-Al1.0Sc0.0N thin film is 4.9 pm per Volt. The highest enhancement in the d33-eff value occurred in the wz-Al0.58Sc0.42N thin film. Above x = 0.42, the d33-eff reduces due to phase-mixing of the wz-Al1-xScxN phase with cubic-Sc3AlN phase till the piezoelectricity finally disappear at x = 0.51
Materials Science (cond-mat.mtrl-sci)
20 pages, 10 figures (some containing multiple figures)
Photocurrent generation from spin dynamics in antiferromagnetic Dirac semimetals
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-05-07 20:00 EDT
Kohei Hattori, Hikaru Watanabe, Ryotaro Arita
Using real-time simulations, we explore the photocurrent induced by localized spin dynamics in antiferromagnetic Dirac semimetals. These materials exhibit strong spin-charge coupling because the energy scales of the electronic and spin systems are of the same order. The photocurrent response exhibits a pronounced peak reflecting the presence of the Dirac point at the resonance frequency of the localized spin system. This contribution plays a crucial role in the photocurrent generation when the electronic filling is set around the Dirac nodes in the Dirac semimetal. We also reveal that the photocurrent response exhibits a low-frequency divergence due to the modulation of the resonance frequency of the localized spin system. Our findings clarify that the photocurrent response arising from the spin dynamics reflects the band topology of the Dirac semimetals, and the localized spin dynamics plays an important role in the photocurrent generation.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Strongly Correlated Electrons (cond-mat.str-el)
6 pages, 4 figures
Stable partial dislocation complexes in GaN as charge carrier lifetime modifiers for terahertz device applications by molecular dynamics and first-principle simulations
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-05-07 20:00 EDT
Wurtzite GaN is a promising material for applications in photoconductive THz radiation sources. For this purpose, the photogenerated charge carriers lifetime of the order of tenths of picoseconds is required. A controllable lifetime reduction may be considered to achieve by creating recombination active stable dislocation complexes formed by mobile basal-plane Shockley partial dislocations (PDs). In this work, formation pathways and stability of PD complexes in basal planes of wurzite GaN are studied by molecular dynamics (MD) simulations. The simulations reveal the formation of stable complexes by attractive interaction of two 30° or two 90° PDs with opposite Burgers vectors located in consecutive (0001) planes. Ones formed, these complexes change neither their positions, not the atomic configurations during simulated anneal at 1500 K up to the times of 5 ns. The MD results are used as an input for density functional theory calculations to refine the atomic structures of the complex cores and to investigate their electronic properties. The calculated band structures of GaN with 30°-30° and 90°-90° dislocation complexes indicate localized energy levels in the band gap near the top of the valence band and the conduction band bottom. The calculations of the partial electronic states density confirm the possibility of electron-hole recombination between the states localized at the PD complex cores. These recombination characteristics are distinctly reflected in the calculated absorption spectra. We conclude that creating such PD complexes in required concentration may be a tool for tailoring the recombination properties of wurtzite GaN for THz radiation generation applications.
Materials Science (cond-mat.mtrl-sci)
26 pages, 10 figures, includes supplementary information
Equilibrium, Relaxation and Fluctuations in homogeneous Bose-Einstein Condensates: Linearized Classical Field Analysis
New Submission | Quantum Gases (cond-mat.quant-gas) | 2025-05-07 20:00 EDT
Nils A. Krause, Ashton S. Bradley
We present a thorough analysis of the linearized stochastic projected Gross-Pitaevskii equation (SPGPE) describing finite temperature in Bose-Einstein condensates (BECs). Our study reveals an optimal choice for the cut-off that divides the Bose gas into a low energy coherent region forming a classical wave and a high energy thermal cloud acting as a reservoir. Moreover, it highlights the relevance of energy damping, the number conserving scattering between thermal and coherent atoms. We analyze the equilibrium properties and near equilibrium relaxation of a homogeneous BEC in one, two and three dimensions at high phase space density, and calculate the autocorrelation function and power spectrum of the density and phase fluctuations. Simulations of the full non-linear SPGPE are in close agreement, and extend our arguments beyond the linear regime. Our work suggests the need for a re-examination of decay processes in BECs studied under the neglect of energy damping.
Quantum Gases (cond-mat.quant-gas)
Proximity Induced Non-collinear Magnetic States in Planar Superconductor/Ferromagnet Hybrids
New Submission | Superconductivity (cond-mat.supr-con) | 2025-05-07 20:00 EDT
A. A. Kopasov, S. V. Mironov, A. S. Mel’nikov
The proximity induced superconducting (S) correlations in ferromagnetic (F) layers of planar S/F hybrids are shown to be responsible for the appearance of a nonlinear interaction between the magnetic moments of the F layers. This interaction originates from the combined influence of the orbital and exchange phenomena and can result in the spontaneous formation of non-collinear magnetic states in these systems. The proposed nonlinear coupling mechanism and resulting changes of magnetic textures are crucial for the design of the superconducting spintronics devices exploiting the long-range spin triplet proximity effect.
Superconductivity (cond-mat.supr-con), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
11 pages, 3 figures
Phys. Rev. B 110, 214501 (2024)
Multilayer Crystal Field states from locally broken centrosymmetry
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-05-07 20:00 EDT
Owen Moulding, Makoto Shimizu, Amit Pawbake, Yingzheng Gao, Sitaram Ramakrishnan, Gaston Garbarino, Nubia Caroca-Canales, Jérôme Debray, Clément Faugeras, Christoph Geibel, Youichi Yanase, Marie-Aude Méasson
Local charge, spin, or orbital degrees of freedom with intersite interactions are oftentimes sufficient to construct most quantum orders. This is conventionally true for f-electron systems, where the extent of the f-electrons and their associated crystal-electric-field (CEF) states are strongly localized. Here, polarized Raman spectroscopy measurements of a locally non-centrosymmetric compound, CeCoSi, unveil more CEF excitations than expected in the local model. We interpret this as experimental evidence for the entanglement of CEF states between cerium layers. This composite sublattice, spin, and orbital degree of freedom provides an unconsidered means to form novel orders, not only in this system, but in any system exhibiting globally preserved yet locally broken centrosymmetry.
Strongly Correlated Electrons (cond-mat.str-el), Superconductivity (cond-mat.supr-con)
17 pages, plus SI, 3 figures
Constraints on magnetism and correlations in RuO$_2$ from lattice dynamics and Mössbauer spectroscopy
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-05-07 20:00 EDT
George Yumnam, Parul R. Raghuvanshi, John D. Budai, Dipanshu Bansal, Lars Bocklage, Douglas Abernathy, Yongqiang Cheng, Ayman Said, Igor I. Mazin, Haidong Zhou, Benjamin A. Frandsen, David S. Parker, Lucas R. Lindsay, Valentino R. Cooper, Michael E. Manley, Raphaël P. Hermann
We provide experimental evidence for the absence of a magnetic moment in bulk RuO$ _2$ , a candidate altermagnetic material, by using a combination of Mössbauer spectroscopy, nuclear forward scattering, inelastic X-ray and neutron scattering, and density functional theory calculations. Using complementary Mössbauer and nuclear forward scattering we determine the $ ^{99}$ Ru magnetic hyperfine splitting to be negligible. Inelastic X-ray and neutron scattering derived lattice dynamics of RuO$ _2$ are compared to density functional theory calculations of varying flavors. Comparisons among theory with experiments indicate that electronic correlations, rather than magnetic order, are key in describing the lattice dynamics.
Materials Science (cond-mat.mtrl-sci), Other Condensed Matter (cond-mat.other)
Sub-micron Cu(In,Ga)Se2 solar cell with efficiency of 18.2% enabled by a hole transport layer
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-05-07 20:00 EDT
Taowen Wang, Longfei Song, Saeed Bayat, Michele Melchiorre, Nathalie Valle, Adrian-Marie Philippe, Emmanuel Defay, Sebastjan Glinsek, Susanne Siebentritt
Reducing the thickness of Cu(In,Ga)Se2 solar cells is a key objective in order to reduce production cost and to improve sustainability. The major challenge for sub-micron Cu(In,Ga)Se2 cells is the recombination at the backside. In standard Cu(In,Ga)Se2 backside recombination is suppressed by a bandgap gradient, acting as a back surface field. This gradient is difficult to maintain in sub-micron thick absorbers. In this study, a hole transport layer passivates the back contact and enables efficient sub-micron Cu(In,Ga)Se2 solar cells without the need of a Ga gradient. The backside passivation by the hole transport layer is as effective as an optimized Ga gradient, resulting in a significant increase in open-circuit voltage by 80 mV in comparison to the reference sample without passivation. Moreover, the hole transport layer exhibits good transport properties, leading to a fill factor as high as 77%. Photoluminescence quantum yield of 0.15% and solar cell efficiency above 18% are demonstrated in sub-micron Cu(In,Ga)Se2 absorbers.
Materials Science (cond-mat.mtrl-sci)
Quasi-bound layer breathing phonons inside perfect dislocations of lattice-relaxed twisted bilayers
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-05-07 20:00 EDT
Using multiscale modelling we investigate layer breathing phonons in MX$ _2$ bilayers (M=Mo,W; X=S,Se) containing dislocations specific for lattice-relaxed moiré superlattices. Spatial modulation of interlayer distance, caused by the dislocations, generates effective potentials that promote emergence of one-dimensional quasi-bound bands of layer breathing modes inside perfect dislocations forming in the bilayers with parallel and antiparallel alignment of layers. We show that for parallel MX$ _2$ bilayers perfect dislocations host several quasi-bound bands, with frequencies above layer breathing mode in rhombohedral-stacked domains, whereas for antiparallel bilayers only a single quasi-bound band arises near the edge dislocation type, having frequencies above the layer breathing mode in 2H-stacked domains.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci)
Displacement and Stress Analysis of an Elastic Hollow Disk: Comparison with Strength of Materials’ Prediction
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-05-07 20:00 EDT
Ken Okamura, Yosuke Sato, Satoshi Takada
This paper analyzes the stress distribution in a two-dimensional elastic disk under diametric loading, with a focus on enhancing the understanding of concrete and rock materials’ mechanical behavior. The study revisits the Brazilian test and addresses its high shear stress issue near loading points by exploring the ring test, which introduces a central hole in the disk. Using dynamic elasticity theory, we derive stress distributions over time and extend the analysis to static conditions. This approach distinguishes between longitudinal and transverse wave effects, providing a detailed stress field analysis. By drawing parallels with curved beam theories, we demonstrate the applicability of dynamic elasticity theory to complex stress problems, offering improved insights into the stress behavior in elastic disks.
Soft Condensed Matter (cond-mat.soft), Classical Physics (physics.class-ph)
11 pages, 4 figures
Synthesis and characterization of a $π$-extended Clar’s goblet
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-05-07 20:00 EDT
Shantanu Mishra, Manuel Vilas-Varela, Igor Rončević, Fabian Paschke, Florian Albrecht, Leo Gross, Diego Peña
Concealed non-Kekulé polybenzenoid hydrocarbons have no sublattice imbalance yet cannot be assigned a classical Kekulé structure, leading to an open-shell ground state with potential application in organic spintronics. They constitute an exceedingly small fraction of the total number of polybenzenoid hydrocarbons that can be constructed for a given number of benzenoid rings, and their synthesis remains challenging. The archetype of such a system is Clar’s goblet (C$ _{38}$ H$ _{18}$ ), a diradical proposed by Erich Clar in 1972 and recently synthesized on a Au(111) surface. Here, we report the synthesis of a pi-extended Clar’s goblet (C$ _{76}$ H$ _{26}$ ), a tetraradical concealed non-Kekulé polybenzenoid hydrocarbon, by a combined in-solution and on-surface synthetic approach. By means of low-temperature scanning tunneling microscopy and atomic force microscopy, we characterized individual molecules adsorbed on a Cu(111) surface. We provide insights into the electronic properties of this elusive molecule, including the many-body nature of its ground and excited states, by mean-field and multiconfigurational quantum chemistry calculations.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Manuscript contains 6 pages and 4 figures; supporting information contains 17 pages and 17 figures
Competitive Adsorption in Polymer Nanocomposites: The Molecular Weight and End-Group Effect Revealed by SANS and MD Simulations
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-05-07 20:00 EDT
Tae Yeon Kong, WooJin Kim, YongJoo Kim, So Youn Kim
Understanding polymer adsorption at interfaces is essential for designing advanced polymer-based nanomaterials with tailored interfacial properties. Although adsorption significantly influences the macroscopic properties of polymer composites and thin films, a comprehensive understanding of molecular weight (MW)-dependent adsorption remains challenging and controversial, particularly in polydisperse polymer systems, due to the limitations of experimental approaches. We investigate competitive adsorption in bidisperse poly(ethylene glycol) (PEG) melts and find that shorter chains preferentially adsorb onto nanoparticle surfaces. Experiments and molecular dynamics simulations reveal that the high density of terminal hydroxyl groups in short PEG chains strengthens hydrogen bonding at the interface, driving enthalpy-driven adsorption despite identical polymer backbones. This leads to a densely packed interfacial layer that alters the conformation of longer chains. These findings highlight the critical role of end-group functionality in interfacial polymer behavior and provide new insights for tailoring nanocomposite properties.
Soft Condensed Matter (cond-mat.soft), Materials Science (cond-mat.mtrl-sci)
Defect-Bound Excitons in Topological Materials
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-05-07 20:00 EDT
Roni Majlin Skiff, Sivan Refaely-Abramson, Raquel Queiroz, Roni Ilan
Excitons, bound states of electrons and holes, are affected by the properties of the underlying band structure of a material. Defects in lattice systems may trap electronic defect states, to which an electron can be excited to form defect-bound excitons. Here, we examine the effect of band topology on excitons in systems with a single-site defect. We show that in the topological phase, when robust, in-gap, ring-shaped electronic states appear around defects, excitons inherit the properties of these ring states: The excitons’ binding energies are lowered as a result of the wide spatial profile of the defect state, and their wave functions have complex shapes and order due to the mixed orbital character of the topological bands. Our study advances the understanding of the role of topology in modifying and controlling defect-bound excitons in quantum materials.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
11 pages, 8 figures
Density of States Proportion on Charge Transfer Kinetics in Breathing Fermionic Systems of Molecules and Materials: A Perspective of Entropy-Ruled Method
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-05-07 20:00 EDT
Conceptualization, theory, method developments and implementations are always of great importance and an interesting task to explore a new dimension in science and technology, which is highly solicited for various functional-driven potential applications (e.g., electronic devices, charge storage devices). Numerous experimental and theoretical studies urge the necessity of a new theory or method to quantify the exact value of charge transport (CT) calculations (e.g., mobility and conductivity) through the appropriate process and methods. With this motivation, the entropy-ruled charge dynamics method has been recently proposed, which unifies band and hopping transport mechanism via quantum-classical transition analogy. Here, the energy (in terms of chemical potential) scaled entropy has a direct proportion with the density of states (DOS); and hence it is termed as DOS proportion. This proportion principally acts as a key descriptor for charge transport calculations in both molecular and materials systems, which is directly connected with all CT quantities like mobility, conductivity, current density etc. This perspective explains a unique nature of entropy-ruled method for the entire transport range from delocalized band to localization (or hopping) transport. The validity and limitations of Einstein relation and Boltzmann approach are discussed with different limits and physical conditions for disordered molecules and periodic systems. Finally, the futuristic scope and expected progress is addressed for correlated electron dynamical systems and devices. It is well-noted that the new DOS proportion and related entropy-ruled transport formalism are fundamentally more important for nurturing semiconducting science and technology towards a new era.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
24 Pages, 5 Figures, 19 main Equations, 6 Sections
Parametrically amplified Josephson plasma waves in YBa_2Cu_3O_(6+x): evidence for local superconducting fluctuations up to the pseudogap temperature $T^*$
New Submission | Superconductivity (cond-mat.supr-con) | 2025-05-07 20:00 EDT
Marios H. Michael, Eugene Demler, Patrick Lee
A number of experiments have reported evidence for the existence of the lower Josephson plasmon mode in underdoped YBCO up to the pseudogap temperature scale when the sample is subject to intense terahertz pulses. Evidences include the observation of a reflectivity edge that resembles that of the superconducting state, and the second harmonic generation of a probe optical pulse that is modulated at a frequency similar the reflectivity feature. Since the lower Josephson plasmon mode is often associated with coherent oscillations between bilayers in the YBCO structure, these experiments have led to the suggestion that the intense pump has created pair coherence up to 350K. In this paper, we propose an alternative explanation of these experiments based on the model of short ranged superconducting correlations in the equilibrium state and using the Floquet perspective to analyze optical responses of the photoexcited state. Our model only requires local pairing with phase correlations that can be very short ranged when the system is at equilibrium at a temperature above Tc but below the pseudo-gap temperature T\ast. Within this assumption there is no phase coherence between bilayers. On the other hand the relative phase between members of the bilayer has a longer in-plane correlation which leads locally to a finite Josephson current. We show that the nonlinearity afforded by the local intra-bilayer Josephson current is sufficient to explain both the reflectivity and second harmonic generation data. The key point is that in the lower Josephson plasmon, the coupling between bilayers is mainly capacitive: the Josepson current between bilayers can be set to zero without affecting the parametric amplification process. The implication is that while superconducting coherence may not be created by the pump, the pseudogap phase must possess a local pairing amplitude at equilibrium.
Superconductivity (cond-mat.supr-con), Strongly Correlated Electrons (cond-mat.str-el), Optics (physics.optics)
10 pages + appendix, 3 figures,
Surface Grafting of Graphene Flakes with Fluorescent Dyes: A Tailored Functionalization Approach
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-05-07 20:00 EDT
Ylea Vlamidis, Carmela Marinelli, Aldo Moscardini, Paolo Faraci, Stefan Heun, Stefano Veronesi
The controlled functionalization of graphene is critical for tuning and enhancing its properties, thereby expanding its potential applications. Covalent functionalization offers a deeper tuning of the geometric and electronic structure of graphene compared to non-covalent methods; however, the existing techniques involve side reactions and spatially uncontrolled functionalization, pushing research toward more selective and controlled methods. A promising approach is 1,3-dipolar cycloaddition, successfully utilized with carbon nanotubes. In the present work, this method has been extended to graphene flakes with low defect concentration. A key innovation is the use of a custom-synthesized ylide with a protected amine group (Boc), facilitating subsequent attachment of functional molecules. Indeed, after Boc cleavage, fluorescent dyes (Atto 425, 465, and 633) were covalently linked via NHS ester derivatization. This approach represents a highly selective method of minimizing structural damage. Successful functionalization was demonstrated by Raman spectroscopy, photoluminescence spectroscopy, and confocal microscopy, confirming the effectiveness of the method. This novel approach offers a versatile platform, enabling its use in biological imaging, sensing, and advanced nanodevices. The method paves the way for the development of sensors and devices capable of anchoring a wide range of molecules, including quantum dots and nanoparticles. Therefore, it represents a significant advancement in graphene-based technologies.
Materials Science (cond-mat.mtrl-sci)
27 pages including Supporting Information, 5 figures in main and 6 figures in SI
Nanomaterials 2025, 15, 329
Effective Field Theory of Superconductivity
New Submission | Superconductivity (cond-mat.supr-con) | 2025-05-07 20:00 EDT
Yoonbai Kim, SeungJun Jeon, Hanwool Song
A field theory of a Schrödinger type complex scalar field of Cooper pair, a U(1) gauge field of electromagnetism, and a neutral scalar field of gapless acoustic phonon is proposed for superconductivity of s-waves. Presence of the gapless neutral scalar field is justified as low energy residual acoustic phonon degrees in the context of effective field theory. The critical coupling of quartic self-interaction of complex scalar field is computed from a 1-loop level interaction balance between the repulsion mediated by massive degree of the U(1) gauge field and the attraction mediated by massive Higgs degree, in the static limit. The obtained net attraction or repulsion in perturbative regime matches the type I or II superconductivity, respectively. We find the new critical coupling of cubic Yukawa type interaction between the neutral and complex scalar fields from another tree level interaction balance between the Coulomb repulsion mediated by massless degree of the U(1) gauge field and the attraction mediated by the gapless neutral scalar field, in the static limit. Superconducting phase is realized at or in the vicinity of this critical coupling. A huge discrepancy between the propagation speeds of photon and phonon gives a plausible explanation on low critical temperatures in conventional superconductors.
Superconductivity (cond-mat.supr-con), Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Strongly Correlated Electrons (cond-mat.str-el), High Energy Physics - Theory (hep-th)
25 pages, 2 figures
Design principles of deep translationally-symmetric neural quantum states for frustrated magnets
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-05-07 20:00 EDT
Rajah P. Nutakki, Ahmedeo Shokry, Filippo Vicentini
Deep neural network quantum states have emerged as a leading method for studying the ground states of quantum magnets. Successful architectures exploit translational symmetry, but the root of their effectiveness and differences between architectures remain unclear. Here, we apply the ConvNext architecture, designed to incorporate elements of transformers into convolutional networks, to quantum many-body ground states. We find that it is remarkably similar to the factored vision transformer, which has been employed successfully for several frustrated spin systems, allowing us to relate this architecture to more conventional convolutional networks. Through a series of numerical experiments we design the ConvNext to achieve greatest performance at lowest computational cost, then apply this network to the Shastry-Sutherland and J1-J2 models, obtaining variational energies comparable to the state of the art, providing a blueprint for network design choices of translationally-symmetric architectures to tackle challenging ground-state problems in frustrated magnetism.
Strongly Correlated Electrons (cond-mat.str-el), Disordered Systems and Neural Networks (cond-mat.dis-nn), Quantum Physics (quant-ph)
14 pages, 7 figures
Robust quantum anomalous Hall effect with spatially uncorrelated disorder
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-05-07 20:00 EDT
In magnetic topological insulators, a phase transition between quantum anomalous Hall (QAH) and Anderson localization insulating phases can be triggered by the rotation of an applied magnetic field. Without the scattering paths along magnetic domains, this phase transition is governed by scattering induced by nonmagnetic disorder. We show that the QAH phase is strikingly robust in the presence of spatially uncorrelated disorder. The robustness is attributed to a resilience of the topological band gap against disorder, induced by quantum confinement. The critical behavior near the phase transition suggests that the scattering is distinct from quantum percolation. This provides new insights on the robustness of the QAH effect in magnetic topological insulators with atomic defects, impurities, and dopants.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Main Text (6 pages, 4 figures) and Supplemental Material (8 pages, 4 figures)
Intrinsic Attractive and Repulsive Interactions: From Classical to Quantum Gases in the Generalized Maxwell-Boltzmann Distribution
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-05-07 20:00 EDT
Maryam Seifi, Zahra Ebadi, Hamzeh Agahi, Hossein Mehri-Dehnavi, Hosein Mohammadzadeh
The thermodynamic parameter space is flat for an ideal classical gas with non-interacting particles. In contrast, for an ideal quantum Bose (Fermi) gas, the thermodynamic curvature is positive (negative), indicating intrinsic attractive (repulsive) interactions. We generalize the classical Maxwell-Boltzmann distribution by employing a generalized form of the exponential function, proposing the Mittag-Leffler Maxwell-Boltzmann distribution within the framework of superstatistics. We demonstrate that the generalization parameter, $ \alpha$ , quantifies the statistical interaction. When $ \alpha = 1$ , the distribution coincides with the standard classical Maxwell-Boltzmann distribution, where no statistical interaction is present. For $ 0 < \alpha < 1$ ($ \alpha > 1$ ), the statistical interaction is repulsive (attractive), corresponding to a negative (positive) thermodynamic curvature of the system.
Statistical Mechanics (cond-mat.stat-mech)
12 pages,11 figures
Clarification of the Spontaneous Polarization Direction in Crystals with Wurtzite Structure
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-05-07 20:00 EDT
Simon Fichtner, Mohamed Yassine, Chris van de Walle, Oliver Ambacher
The wurtzite structure is one of the most frequently found crystal structures in modern semiconductors and its inherent spontaneous polarization is a defining materials property. Despite this significance, confusion has been rampant in the literature with respect to the orientation of the spontaneous polarization inside the unit cell of the wurtzite structure, especially for the technologically very relevant III-N compounds (AlN, GaN, InN). In particular, the spontaneous polarization has been reported to either point up or down for the same unit cell orientation, depending on the literature source - with important implications for, e.g., the carrier type and density expected at interfaces of heterostructures involving materials with wurtzite-structure. This perspective aims to resolve this ambiguity by reviewing available reports on the direction of the energetically preferred polarization direction in the presence of external electric fields, as well as atomically resolved scanning transmission electron microscopy images. While we use ferroelectric wurtzite AlScN as a key example, our conclusions are generalizable to other compounds with the same crystal structure. We demonstrate that a metal-polar unit cell must be associated with an upward polarization vector - which is contrary to long-standing conventional wisdom.
Materials Science (cond-mat.mtrl-sci)
Appl. Phys. Lett. 125, 040501 (2024)
Defect analysis of the $β$- to $γ$-Ga${2}$O${3}$ phase transition
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-05-07 20:00 EDT
Umutcan Bektas, Maciej O. Liedke, Huan Liu, Fabian Ganss, Maik Butterling, Nico Klingner, René Hübner, Ilja Makkonen, Andreas Wagner, Gregor Hlawacek
In this study, we investigate the ion-irradiation-induced phase transition in gallium oxide (Ga2O3) from the $ \beta$ to the $ \gamma$ phase, the role of defects during the transformation, and the quality of the resulting crystal structure. Using a multi-method analysis approach including X-ray diffraction (XRD), transmission electron microscopy (TEM), Rutherford backscattering spectrometry in channeling mode (RBS/c), Doppler broadening variable energy positron annihilation spectroscopy (DB-VEPAS) and variable energy positron annihilation lifetime spectroscopy (VEPALS) supported by density functional theory (DFT) calculations, we have characterized defects at all the relevant stages before, during, and after the phase transition. Reduction in backscattering yield was observed in RBS/c spectra after the transition to the $ \gamma$ phase. This is corroborated by a significant decrease in the positron trapping center density due to generation of embedded vacancies intrinsic for the $ \gamma$ -Ga2O3 but too shallow in order to trap positrons. A comparison of the observed positron lifetime of $ \gamma$ -Ga2O3 with different theoretical models shows good agreement with the three-site $ \gamma$ phase approach. A characteristic increase in the effective positron diffusion length and the positron lifetime at the transition point from $ \beta$ -Ga2O3 to $ \gamma$ -Ga2O3 enables visualization of the phase transition with positrons for the first time. Moreover, a subsequent reduction of these quantities with increasing irradiation fluence was observed, which we attribute to further evolution of the $ \gamma$ -Ga2O3 and changes in the gallium vacancy density as well as relative occupation in the crystal lattice.
Materials Science (cond-mat.mtrl-sci)
Crystal structural evolution of Ru$_3$Sn$_7$ under pressure and its implication on possible electronic changes
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-05-07 20:00 EDT
K. A. Irshad, P. Anees, Hrudananda Jena, Boby Joseph
Ru$ _3$ Sn$ _7$ , an intermetallic compound with advanced catalytic properties, exhibits a complex crystal structure and intriguing electronic properties, making it an attractive candidate for investigations under high-pressure (HP). The structural, vibrational and electronic band structure of this compound were investigated at HP up to ~ 20 GPa using synchrotron x-ray powder diffraction, micro-Raman, and density functional theory (DFT), respectively. Despite the local structural changes implied by a discernible reduction in the compressibility and distinct slope changes in the pressure evolution of the symmetric stretching vibrations of the Ru and Sn atoms around 8 GPa, the cubic structure is found to be stable throughout the pressure range. In support, our calculated phonon dispersion relation confirmed the stability of the cubic phase till the highest pressures. A comprehensive analysis of the Raman spectrum reveals the signatures of the pressure induced sudden strengthening of electron-phonon coupling as early as 3 GPa which is backed by a bounce in the phonon and electron density of states (DoS). Electronic structure calculations demonstrate that the metallic nature of Ru$ _3$ Sn$ _7$ is preserved in the studied pressure range with a minor redistribution of electronic DoS across the Fermi level (EF). The band structure calculations predict intriguing changes in the electronic structure, revealing the pressure induced dp hybridization through the high symmetry point of the Brillouin zone which is largely responsible for the observed reduction in the compressibility and enhancement of the electron-phonon coupling in Ru$ _3$ Sn$ _7$ .
Materials Science (cond-mat.mtrl-sci)
Computational assessment of non-polar and polar GaP terminations for photoelectrochemical water splitting
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-05-07 20:00 EDT
Sofia Apergi, Sreejith Pallikkara Chandrasekharan, Charles Cornet, Laurent Pedesseau
With photoelectrochemical water splitting being one of the most promising approaches for clean energy production and storage, the search for efficient photoelectrode materials is greater than ever. Gallium phosphide (GaP) is a well-established semiconductor with suitable band edge positions that has already been successfully employed in photoelectrochemical solar cells. However, to utilize it as efficiently as possible, a proper understanding of its properties when interfaced with water is required, and this is currently lacking. In this work we use ab initio molecular dynamics simulations to study the properties of the aqueous interfaces of various GaP non-polar (110) and polar (001) terminations. We calculate their band alignment with respect to the standard hydrogen electrode potential and investigate their interfacial structural properties. Based on these properties we assess the capability of the various terminations to catalyze the reactions associated with water splitting and propose approaches for improving the performance of GaP for application in PECs.
Materials Science (cond-mat.mtrl-sci)
Self-Organized Three-Dimensional Superstructures, Spinodal Decomposition, and Mechanical Response of Epitaxial Hf$_{1-x}$Al$_x$N Thin Films
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-05-07 20:00 EDT
M. Lorentzon, N. Takata, T. Zhu, G. Greczynski, R. Hahn, A. Zubayer, J. Palisaitis, H. Riedl, D. Kim, L. Hultman, J. Birch, N. Ghafoor
Transition metal aluminum nitrides are a technologically important class of multifunctional ceramics. While the HfAlN system is to a large extent unexplored, we study phase stability, nanostructure design, and mechanical properties of rocksalt cubic (c-) phase and wurtzite-hexagonal (h-) phase Hf$ _{1-x}$ Al$ _x$ N$ _y$ thin films grown on MgO(001) substrates using ion-assisted reactive magnetron sputtering. Single-crystal c-Hf$ _{1-x}$ Al$ _x$ N$ _y$ films were obtained with $ x < 0.30$ . Spinodal decomposition taking place during film deposition resulted in a three-dimensional checkerboard superstructure of AlN-rich and HfN-rich nanodomains, as opposed to a metastable cubic solid solution. Lattice-resolved scanning transmission electron microscopy and x-ray and electron diffraction reveals that the superstructure period is along all three <100> directions and scales almost linearly between 9-13 A with increasing Al content. For $ x > 0.41$ , however, nanocrystalline h-Hf$ _{1-x}$ Al$ _x$ N$ _y$ consisting of segregated Hf- and Al-rich nanodomains in a (0001) fiber texture forms. The nanoindentation hardness of these films increases sharply with x, from 26 GPa for HfNy, to 38 GPa for c-Hf$ _{1-x}$ Al$ _x$ N$ _y$ , due to dislocation pinning at the superstructure strain fields. The hardness drops to 22 GPa for the softer h-Hf1-xAlxNy, still remaining considerably higher than that of a binary AlN. In micropillar compression testing, c-Hf$ _{0.93}$ Al$ _{0.07}$ N$ _{1.15}$ exhibits a linear elastic response up until strain burst, with brittle fracture occurring at a much higher yield stress compared to HfN$ _y$ , on {110}<011> slip systems, which is attributed to superstructure inhibited dislocation motion. In contrast, h-Hf$ _{0.59}$ Al$ _{0.41}$ N$ _{1.23}$ exhibits limited plasticity and a high yield stress followed by strain burst, attributed to the nanocrystalline structure.
Materials Science (cond-mat.mtrl-sci)
Interparticle heterostructures by spontaneous formation of Dirac nodal arc semimetal PtSn4 domains in nanoparticles produced by Supersonic Cluster Beam Deposition
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-05-07 20:00 EDT
Marc Heggen, José Enrique Martinez Medina, Emanuele Barborini
In this study, we report on the spontaneous formation of highly ordered 2D layered domains of intermetallic phase PtSn4 in Sn nanoparticles of dimensions of the order of 10 nm during the gas aggregation process occurring in Supersonic Cluster Beam Deposition. Phase identification is based on High Resolution Transmission Electron Microscopy and on X-ray emission analysis coupled with Scanning Transmission Electron Microscopy. We propose that PtSn4-ordered domains precipitate inside Sn nanoparticles once the temperature drops below 520°C upon collisional cooling with room temperature Argon, while the nanoparticles persist longer in a liquid state. Sn matrix eventually solidifies upon the sudden temperature drop due to the supersonic expansion. 2D-layered PtSn4 domains create interparticle heterostructures that disrupt the spherical symmetry typical of gas aggregation processes and separate the Sn particle into distinct parts. The Dirac nodal arc semimetal character of PtSn4 makes it particularly interesting for studying the transport mechanisms in nanogranular films obtained by the soft-assembling of such nanoparticles, which feature a network of heterostructures showing sequences of alternate PtSn4 2D domains and metallic \b{eta}-Sn necks.
Materials Science (cond-mat.mtrl-sci)
Manuscript intended as a letter, with 6 pages and 4 images
Active Learning for Predicting Polymer/Plasticizer Phase Behaviour
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-05-07 20:00 EDT
Lois Smith, Jessica Steele, Hossein Ali Karimi-Varzaneh, Paola Carbone
Plasticisers (PLs) are small additives commonly incorporated into polymer composites to enhance processability and improve mechanical properties. Their effectiveness depends heavily on their miscibility within the polymer melt, yet isolating the influence of plasticiser properties, such as flexibility and geometry, remains challenging. This difficulty stems from the time consuming nature of experimental work and also from the presence of impurities and inconsistencies that often arise during synthesis and testing. Atomistic simulations face similar difficulties as phase separation can occur over microsecond timescales, which can be computationally expensive. In this work, we use a coarse-grained bead-and-spring model to screen plasticisers of varying flexibilities and geometries to build a pool-based active learning procedure which characterizes their design space and its effect on polymer/plasticiser miscibility. We perform an active learning cycle with a random forest model and an uncertainty/random hybrid query strategy to determine the miscibility behaviour of queried molecules. This is evaluated through computationally expensive, coarse-grained polymer/plasticiser simulations of a cis-(1,4)-polyisoprene melt filled with small hydrocarbon additives of varying sizes and rigidities. Through this, we are able to efficiently improve model performance in order to make predictions on the entire PL design space. Such findings enable us to determine a new set of general plasticiser design rules, suitable for non-polar molecules, which expands on our previous work. To further prove this, we perform atomistic simulations of polyisoprene/plasticiser systems which are approximately back-mapped from their coarse-grained equivalents. Our findings indicate that the polyisoprene/plasticiser phase behaviour, observed using the coarse-grained model for PLs in the absence of side chains, is valid.
Soft Condensed Matter (cond-mat.soft)
Accelerating the development of oxynitride thin films: A combinatorial investigation of the Al-Si-O-N system
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-05-07 20:00 EDT
Stefanie Frick (1), Oleksandr Pshyk (1), Arnold Müller (2), Alexander Wieczorek (1), Kerstin Thorwarth (1), Sebastian Siol (1) ((1) Empa, Swiss Federal Laboratories for Materials Science and Technology, Dübendorf, Switzerland (2) Laboratory of Ion Beam Physics, ETH Zurich, Zürich, Switzerland)
Oxynitrides are used in a variety of applications including photocatalysts, high-k dielectrics or wear-resistant coatings and often show intriguing multi-functionality. To accelerate the co-optimization of the relevant material properties of these compositionally complex oxynitride systems, high-throughput synthesis and characterization methods are desirable. In the present work, three approaches were investigated to obtain orthogonal anion and cation gradients on the same substrate by magnetron sputtering. The different approaches included varying positions of the local reactive gas inlets and different combinations of target materials. The best performing approach was applied to screen a large two-dimensional area of the quaternary phase space within the Al-Si-O-N system. This material system is a promising candidate for transparent protective coatings with variable refractive indices. With only five depositions of combinatorial libraries, an anion composition range of 2-46% O/(N+O) and a cation composition range of 4-44% Si/(Al+Si) is covered. For lower oxygen and silicon contents, a region with hardness of up to 25 GPa is observed, where the material exhibits either wurtzite AlN or a composite microstructure. By increasing the deposition temperature to 400 °C, an extension of this region can be achieved. At higher oxygen and silicon contents, the structure of the samples is X-ray amorphous. In this structural region, an intimate correlation between hardness and refractive index is confirmed. The results of this study introduce a practical approach to perform high-throughput development of mixed anion materials, which is transferable to many materials systems and applications.
Materials Science (cond-mat.mtrl-sci)
Leveraging high fluence and low pressure for pulsed laser deposition of high-mobility $γ$-Al$_2$O$_3$/SrTiO$_3$ heterostructure growth
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-05-07 20:00 EDT
Thor Hvid-Olsen, Christina Hoegfeldt, Amit Chanda, Alessandro Palliotto, Dae-Sung Park, Thomas Sand Jespersen, Felix Trier
High-mobility oxide heterostructures could be applied for high-frequency devices, transparent conductors, and spin-orbit logic devices. SrTiO$ _3$ is one of the most studied oxide substrate materials for heterostructures. To date, the highest SrTiO3-based charge carrier mobility at 2 K was measured in the interfacial 2-dimensional electron gas (2DEG) of $ \gamma$ -Al$ _2$ O$ _3$ /SrTiO$ _3$ . The formation mechanism and origin of the high electron mobility are not yet fully understood. This investigation presents a successful growth protocol to synthesise high mobility $ \gamma$ -Al$ _2$ O$ _3$ /SrTiO$ _3$ interfaces, and a description of the underlying growth optimisation. Furthermore, indicative features of high-mobility $ \gamma$ -Al$ _2$ O$ _3$ /SrTiO$ _3$ , including the room-temperature sheet resistance, are presented. Signs of epitaxial and crystalline growth are found in a high-mobility sample ($ \mu^{10K} = 1.6 \times 10^4 \mathrm{cm}^2/\mathrm{Vs}$ ). Outlining the growth mechanisms and comparing 40 samples, indicates that high-fluence ($ F > 3\mathrm{J}/\mathrm{cm}^2$ ) and low pressure ($ P \approx 1 \times 10^{-6} \mathrm{mbar}$ ) are essential growth parameters for high-mobility $ \gamma$ -Al$ _2$ O$ _3$ /SrTiO$ _3$ interfaces.
Materials Science (cond-mat.mtrl-sci)
Bridging constrained random-phase approximation and linear response theory for computing Hubbard parameters
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-05-07 20:00 EDT
Alberto Carta, Iurii Timrov, Sophie Beck, Claude Ederer
The predictive accuracy of popular extensions to density-functional theory (DFT) such as DFT+U and DFT plus dynamical mean-field theory (DFT+DMFT) hinges on using realistic values for the screened Coulomb interaction U. Here, we present a systematic comparison of the two most widely used approaches to compute this parameter, linear response theory (LRT) and the constrained random-phase approximation (cRPA), using a unified framework based on the use of maximally localized Wannier functions to define the underlying basis sets. We demonstrate good quantitative agreement between LRT and cRPA in cases where the strongly interacting subspace corresponds to an isolated set of bands. Differences can be assigned to neglecting the response of the exchange-correlation potential in cRPA and the presence of additional screening channels in LRT. Moreover, we show that in cases with strong hybridization between interacting and screening subspaces, the application of cRPA becomes ambiguous and can lead to unrealistically small U values, while LRT remains well-behaved. Our work clarifies the relation between both methods, sheds light on their strengths and limitations, and emphasizes the importance of using a consistent set of Wannier orbitals to ensure transferability of U values between different implementations.
Strongly Correlated Electrons (cond-mat.str-el)
Large Topological Magnetic Optical Effects and Imaging of Antiferromagnetic Octupole Domains of an Altermagnet-like Weyl Semimetal
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-05-07 20:00 EDT
Xingyue Han, Xiaoran Liu, Mikhail Kareev, Jak Chakhalian, Liang Wu
Pyrochlore iridates have attracted significant interest due to their complex phase behavior arising from the interplay among electron correlations, quantum metric in flat bands, geometrically frustrated lattices, and topology induced by strong spin-orbit coupling. In this study, we focus on Eu$ _2$ Ir$ _2$ O$ _7$ thin films oriented along the (111) crystallographic direction. This quantum material, identified as an antiferromagnetic Weyl semimetal, exhibits a large anomalous Hall effect in transport experiments. Here we employ optical circular dichroism microscopy, to directly image ferroic octupole order and resolve all-in–all-out and all-out–all-in antiferromagnetic domains below the Néel temperature. Remarkably, despite the absence of a detectable net magnetic moment at zero applied magnetic field, we detected a large magnetic circular dichroism signal ($ \sim 10^{-4}$ ) and Kerr effect ($ \sim 10^{-4}$ radians) in zero magnetic field attributable to Berry curvature effects from Weyl nodes. Eu$ _2$ Ir$ _2$ O$ _7$ is a non-collinear magnet with vanishing net moment and magnetic octupole order, similar to the recently proposed collinear d-wave altermagnets, allowing for magneto-optical responses and anomalous Hall effect. This finding likely represents the first demonstration of magnetic circular dichroism and Kerr effect in a topologically non-trivial quantum antiferromagnet with a vanishing net magnetization. Our work opens up the possibility of ultrafast domain switching in the terahertz frequency and the domain wall dynamics in the magnetic Weyl systems, which establishes the foundation for topological antiferromagnetic spintronics.
Materials Science (cond-mat.mtrl-sci)
Nematic ordering via vertical stratification in drying clay nanotube suspensions
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-05-07 20:00 EDT
Arun Dadwal, Meenu Prasher, Nitin Kumar
Evaporative self-assembly offers a simple, cost-effective method for producing functional nanostructured materials. However, achieving tunable and ordered assemblies remains challenging, especially when working with complex building blocks like nanoparticles that exhibit significant shape and size polydispersity. In this study, starting from an aqueous suspension of a polydisperse sample of rod-like Halloysite nanotubes, we present a physical protocol for producing a high degree of orientational ordering in the final dried deposit. By placing a sessile droplet on a substrate heated to 50°C, self-induced Marangoni flows suppress the coffee-ring effect, enabling more uniform deposition of colloidal rods. Subsequently, the vertical stratification during evaporation leads to the segregation of particles by aspect ratio, with longer rods (aspect ratio>=6.5) preferentially migrating to the top layers over the entire deposit. Since rods exceeding this threshold exhibit nematic ordering at high densities, the resulting top layer, spanning an area of the order of mm^2, displays a high degree of orientational order. Thus, our results highlight a robust strategy for engineering ordered structures from disordered colloidal suspensions despite the overall polydispersity of the system.
Soft Condensed Matter (cond-mat.soft)
9 pages, 6 figures
Anomalous proximity effect under Andreev and Majorana bound states
New Submission | Superconductivity (cond-mat.supr-con) | 2025-05-07 20:00 EDT
Eslam Ahmed, Yukio Tanaka, Jorge Cayao
We theoretically study the anomalous proximity effect in a ballistic normal metal/diffusive normal metal/superconductor junction based on Rashba semiconductor nanowire model. The system hosts two distinct phases: a trivial helical phase with zero-energy Andreev Bound States and a topological phase with Majorana Bound States. We analyze the local density of states and induced pair correlations at the edge of the normal metal region. We investigate their behavior under scalar onsite disorder and changing the Superconductor and diffusive regions lengths in the trivial helical and topological phases. We find that both phases exhibit a zero-energy peak in the local density of states and spin-triplet pair correlations in the clean limit, which we attribute primarily to odd-frequency spin-triplet pairs. Disorder rapidly splits the zero-energy peak in the trivial helical phase regardless of the lengths of the superconductor and diffusive normal regions. The zero-energy peak in the topological phase show similar fragility when the superconductor region is short. However, for long superconductor regions, the zero-energy peak in the topological phase remain robust against disorder. In contrast, spin-singlet correlations are suppressed near zero energy in both phases. Our results highlight that the robustness of the zero-energy peak against scalar disorder, contingent on the Superconductor region length, serves as a key indicator distinguishing trivial Andreev bound states from topological Majorana bound states.
Superconductivity (cond-mat.supr-con), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
13 pages, 9 figures
Critical habitat size of organisms diffusing with stochastic resetting
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-05-07 20:00 EDT
Luiz Menon, Pablo de Castro, Celia Anteneodo
The persistence of populations depends on the minimum habitat area required for survival, known as the critical patch size. While most studies assume purely diffusive movement, additional movement components can significantly alter habitat requirements. Here, we investigate how critical patch sizes are affected by stochastic resetting, where each organism intermittently returns to a common fixed location, modeling behaviors such as homing, refuge-seeking, or movement toward essential resources. We analytically derive the total population growth over time and the critical patch size. Our results are validated by agent-based simulations, showing excellent agreement. Our findings demonstrate that stochastic resetting can either increase or decrease the critical patch size, depending on the reset rate, reset position, and external environmental hostility. These results highlight how intermittent relocation shapes ecological thresholds and may provide insights for ecological modeling and conservation planning, particularly in fragmented landscapes such as in deforested regions.
Statistical Mechanics (cond-mat.stat-mech), Biological Physics (physics.bio-ph)