CMP Journal 2025-04-02
Statistics
Nature: 17
Nature Materials: 2
Nature Physics: 1
Physical Review Letters: 7
Physical Review X: 2
arXiv: 61
Nature
Photoinduced copper-catalysed deracemization of alkyl halides
Original Paper | Asymmetric catalysis | 2025-04-01 20:00 EDT
Feng Zhong, Renhe Li, Binh Khanh Mai, Peng Liu, Gregory C. Fu
Deracemization is an emerging strategy for generating enantioenriched compounds wherein the two enantiomers of a readily available racemic starting material are transformed into a single enantiomer, typically through the action of a light-induced catalyst1,2. Excellent proof of principle for this potentially powerful approach to asymmetric catalysis has been described3,4,5,6,7,8; nevertheless, substantial challenges have not yet been addressed, including the exploitation of carbon-heteroatom (rather than only carbon-hydrogen and carbon-carbon) bond cleavage to achieve deracemization, as well as the development of processes that provide broad classes of useful enantioenriched compounds and tetrasubstituted stereocentres. Here we describe a straightforward method that addresses these challenges, using a chiral copper catalyst, generated in situ from commercially available components, to achieve the photoinduced deracemization of tertiary (and secondary) alkyl halides through carbon-halogen bond cleavage. Mechanistic studies (including the independent synthesis of postulated intermediates, photophysical, spectroscopic and reactivity studies, and density functional theory calculations) provide support for the key steps and intermediates in our proposed catalytic cycle, as well as insight into the origin of enantioselectivity.
Asymmetric catalysis, Synthetic chemistry methodology, Photocatalysis
A natural experiment on the effect of herpes zoster vaccination on dementia
Original Paper | Dementia | 2025-04-01 20:00 EDT
Markus Eyting, Min Xie, Felix Michalik, Simon Heß, Seunghun Chung, Pascal Geldsetzer
Neurotropic herpesviruses may be implicated in the development of dementia1,2,3,4,5. Moreover, vaccines may have important off-target immunological effects6,7,8,9. Here we aim to determine the effect of live-attenuated herpes zoster vaccination on the occurrence of dementia diagnoses. To provide causal as opposed to correlational evidence, we take advantage of the fact that, in Wales, eligibility for the zoster vaccine was determined on the basis of an individual’s exact date of birth. Those born before 2 September 1933 were ineligible and remained ineligible for life, whereas those born on or after 2 September 1933 were eligible for at least 1 year to receive the vaccine. Using large-scale electronic health record data, we first show that the percentage of adults who received the vaccine increased from 0.01% among patients who were merely 1 week too old to be eligible, to 47.2% among those who were just 1 week younger. Apart from this large difference in the probability of ever receiving the zoster vaccine, individuals born just 1 week before 2 September 1933 are unlikely to differ systematically from those born 1 week later. Using these comparison groups in a regression discontinuity design, we show that receiving the zoster vaccine reduced the probability of a new dementia diagnosis over a follow-up period of 7 years by 3.5 percentage points (95% confidence interval (CI) = 0.6-7.1, P = 0.019), corresponding to a 20.0% (95% CI = 6.5-33.4) relative reduction. This protective effect was stronger among women than men. We successfully confirm our findings in a different population (England and Wales’s combined population), with a different type of data (death certificates) and using an outcome (deaths with dementia as primary cause) that is closely related to dementia, but less reliant on a timely diagnosis of dementia by the healthcare system10. Through the use of a unique natural experiment, this study provides evidence of a dementia-preventing or dementia-delaying effect from zoster vaccination that is less vulnerable to confounding and bias than the existing associational evidence.
Dementia, Viral infection
Mastering diverse control tasks through world models
Original Paper | Computer science | 2025-04-01 20:00 EDT
Danijar Hafner, Jurgis Pasukonis, Jimmy Ba, Timothy Lillicrap
Developing a general algorithm that learns to solve tasks across a wide range of applications has been a fundamental challenge in artificial intelligence. Although current reinforcement-learning algorithms can be readily applied to tasks similar to what they have been developed for, configuring them for new application domains requires substantial human expertise and experimentation1,2. Here we present the third generation of Dreamer, a general algorithm that outperforms specialized methods across over 150 diverse tasks, with a single configuration. Dreamer learns a model of the environment and improves its behaviour by imagining future scenarios. Robustness techniques based on normalization, balancing and transformations enable stable learning across domains. Applied out of the box, Dreamer is, to our knowledge, the first algorithm to collect diamonds in Minecraft from scratch without human data or curricula. This achievement has been posed as a substantial challenge in artificial intelligence that requires exploring farsighted strategies from pixels and sparse rewards in an open world3. Our work allows solving challenging control problems without extensive experimentation, making reinforcement learning broadly applicable.
Computer science, Mathematics and computing
Bifidobacteria support optimal infant vaccine responses
Original Paper | Microbiome | 2025-04-01 20:00 EDT
Feargal J. Ryan, Michelle Clarke, Miriam A. Lynn, Saoirse C. Benson, Sonia McAlister, Lynne C. Giles, Jocelyn M. Choo, Charné Rossouw, Yan Yung Ng, Evgeny A. Semchenko, Alyson Richard, Lex E. X. Leong, Steven L. Taylor, Stephen J. Blake, Joyce I. Mugabushaka, Mary Walker, Steve L. Wesselingh, Paul V. Licciardi, Kate L. Seib, Damon J. Tumes, Peter Richmond, Geraint B. Rogers, Helen S. Marshall, David J. Lynn
Accumulating evidence indicates that antibiotic exposure may lead to impaired vaccine responses1,2,3,4; however, the mechanisms underlying this association remain poorly understood. Here we prospectively followed 191 healthy, vaginally born, term infants from birth to 15 months, using a systems vaccinology approach to assess the effects of antibiotic exposure on immune responses to vaccination. Exposure to direct neonatal but not intrapartum antibiotics was associated with significantly lower antibody titres against various polysaccharides in the 13-valent pneumococcal conjugate vaccine and the Haemophilus influenzae type b polyribosylribitol phosphate and diphtheria toxoid antigens in the combined 6-in-1 Infanrix Hexa vaccine at 7 months of age. Blood from infants exposed to neonatal antibiotics had an inflammatory transcriptional profile before vaccination; in addition, faecal metagenomics showed reduced abundance of Bifidobacterium species in these infants at the time of vaccination, which was correlated with reduced vaccine antibody titres 6 months later. In preclinical models, responses to the 13-valent pneumococcal conjugate vaccine were strongly dependent on an intact microbiota but could be restored in germ-free mice by administering a consortium of Bifidobacterium species or a probiotic already widely used in neonatal units. Our data suggest that microbiota-targeted interventions could mitigate the detrimental effects of early-life antibiotics on vaccine immunogenicity.
Microbiome, Paediatric research, Systems analysis, Vaccines
Near-field photon entanglement in total angular momentum
Original Paper | Nanophotonics and plasmonics | 2025-04-01 20:00 EDT
Amit Kam, Shai Tsesses, Yigal Ilin, Kobi Cohen, Yaakov Lumer, Lior Fridman, Stav Lotan, Anatoly Patsyk, Liat Nemirovsky-Levy, Meir Orenstein, Mordechai Segev, Guy Bartal
Photons can carry angular momentum, which is conventionally attributed to two constituents–spin angular momentum (SAM), which is an intrinsic property related to the polarization, and orbital angular momentum (OAM), which is related to the photon spatial distribution. In paraxial optics, these two forms of angular momentum are separable1, such that entanglement can be induced between the SAM and the OAM of a single photon2,3 or of different photons in a multi-photon state4. In nanophotonic systems, however, the SAM and the OAM of a photon are inseparable5,6, so only the total angular momentum (TAM) serves as a good quantum number7,8,9. Here we present the observation of non-classical correlations between two photons in the near-field regime, giving rise to entanglement related to the TAM. We entangle those nanophotonic states by coupling photon pairs to plasmonic modes and use quantum imaging techniques10,11 to measure their correlations. We observe that entanglement in TAM leads to a completely different structure of quantum correlations of photon pairs, compared with entanglement related to the two constituent angular momenta. This work paves the way for on-chip quantum information processing using the TAM of photons as the encoding property for quantum information.
Nanophotonics and plasmonics, Quantum optics
Formation and composition of Earth’s Hadean protocrust
Original Paper | Core processes | 2025-04-01 20:00 EDT
Simon Turner, Bernard Wood, Tim Johnson, Craig O’Neill, Bernard Bourdon
Although Earth, together with other terrestrial planets, must have had an early-formed protocrust, the chemical composition of this crust has received little attention. The protocrust was extracted from an extensive magma ocean formed by accretion and melting of asteroidal bodies1. Both experimental and chronological data suggest that the silicate melt ascending from this magma ocean formed in equilibrium with, or after, metal was extracted to form Earth’s core. Here we show that a protocrust formed under these conditions would have had incompatible (with respect to silicate minerals) trace-element characteristics remarkably similar to those of the current average continental crust. This has major implications for subsequent planetary evolution. Many geochemical arguments for when and how plate tectonics began implicitly assume that subduction is required to produce the continental trace-element signature. These arguments are severely compromised if this signature was already a feature of the Hadean protocrust.
Core processes, Geochemistry, Planetary science
Metal-support frontier orbital interactions in single-atom catalysis
Original Paper | Catalyst synthesis | 2025-04-01 20:00 EDT
Xianxian Shi, Zhilin Wen, Qingqing Gu, Long Jiao, Hai-Long Jiang, Haifeng Lv, Hengwei Wang, Jiani Ding, Mason P. Lyons, Alvin Chang, Zhenxing Feng, Si Chen, Yue Lin, Xiaoyan Xu, Pengfei Du, Wenlong Xu, Mei Sun, Yin Li, Bing Yang, Tao Zhang, Xiaojun Wu, Junling Lu
Single-atom catalysts (SACs) with maximized metal use and discrete energy levels hold promise for broad applications in heterogeneous catalysis, energy conversion, environmental science and biomedicine1,2,3,4,5,6,7. The activity and stability of SACs are governed by the pair of metal-adsorbate and metal-support interactions8,9,10. However, the understanding of these interactions with their catalytic performance in nature is challenging. Correlations of activity with the charge state of metal atoms have frequently reached controversial conclusions11,12,13,14,15. Here we report that the activity of palladium (Pd1) SACs exhibits a linear scaling relationship with the positions of the lowest unoccupied molecular orbital (LUMO) of oxide supports across 14 types of semiconductor. Elevation of the LUMO position by reducing the support particle size to a few nanometres boosts a record high activity along with excellent stability in the semi-hydrogenation of acetylene. We show that the elevated LUMO of support reduces its energy gap with the highest occupied molecular orbital (HOMO) of Pd1 atoms, which promotes Pd1-support orbital hybridizations for high stability and further amends the LUMO of anchored Pd1 atoms to enhance Pd1-adsorbate interactions for high activity. These findings are consistent with the frontier molecular orbital theory and provide a general descriptor for the rational selection of metal-support pairs with predictable activity.
Catalyst synthesis, Heterogeneous catalysis
Millimetre-scale bioresorbable optoelectronic systems for electrotherapy
Original Paper | Arrhythmias | 2025-04-01 20:00 EDT
Yamin Zhang, Eric Rytkin, Liangsong Zeng, Jong Uk Kim, Lichao Tang, Haohui Zhang, Aleksei Mikhailov, Kaiyu Zhao, Yue Wang, Li Ding, Xinyue Lu, Anastasia Lantsova, Elena Aprea, Gengming Jiang, Shupeng Li, Seung Gi Seo, Tong Wang, Jin Wang, Jiayang Liu, Jianyu Gu, Fei Liu, Keith Bailey, Yat Fung Larry Li, Amy Burrell, Anna Pfenniger, Andrey Ardashev, Tianyu Yang, Naijia Liu, Zengyao Lv, Nathan S. Purwanto, Yue Ying, Yinsheng Lu, Claire Hoepfner, Altynai Melisova, Jiarui Gong, Jinheon Jeong, Junhwan Choi, Alex Hou, Rachel Nolander, Wubin Bai, Sung Hun Jin, Zhenqiang Ma, John M. Torkelson, Yonggang Huang, Wei Ouyang, Rishi K. Arora, Igor R. Efimov, John A. Rogers
Temporary pacemakers are essential for the care of patients with short-lived bradycardia in post-operative and other settings1,2,3,4. Conventional devices require invasive open-heart surgery or less invasive endovascular surgery, both of which are challenging for paediatric and adult patients5,6,7,8. Other complications9,10,11 include risks of infections, lacerations and perforations of the myocardium, and of displacements of external power supplies and control systems. Here we introduce a millimetre-scale bioresorbable optoelectronic system with an onboard power supply and a wireless, optical control mechanism with generalized capabilities in electrotherapy and specific application opportunities in temporary cardiac pacing. The extremely small sizes of these devices enable minimally invasive implantation, including percutaneous injection and endovascular delivery. Experimental studies demonstrate effective pacing in mouse, rat, porcine, canine and human cardiac models at both single-site and multi-site locations. Pairing with a skin-interfaced wireless device allows autonomous, closed-loop operation upon detection of arrhythmias. Further work illustrates opportunities in combining these miniaturized devices with other medical implants, with an example of arrays of pacemakers for individual or collective use on the frames of transcatheter aortic valve replacement systems, to provide unique solutions that address risks for atrioventricular block following surgeries. This base technology can be readily adapted for a broad range of additional applications in electrotherapy, such as nerve and bone regeneration, wound therapy and pain management.
Arrhythmias, Biomedical engineering, Cardiac device therapy, Implants
A RISC-V 32-bit microprocessor based on two-dimensional semiconductors
Original Paper | Electrical and electronic engineering | 2025-04-01 20:00 EDT
Mingrui Ao, Xiucheng Zhou, Xinjie Kong, Saifei Gou, Sifan Chen, Xiangqi Dong, Yuxuan Zhu, Qicheng Sun, Zhejia Zhang, Jinshu Zhang, Qiran Zhang, Yan Hu, Chuming Sheng, Kaixuan Wang, Shuiyuan Wang, Jing Wan, Jun Han, Wenzhong Bao, Peng Zhou
Recently the quest for post-silicon semiconductors has escalated owing to the inherent limitations of conventional bulk semiconductors, which are plagued by issues such as drain-induced barrier lowering, interfacial-scattering-induced mobility degradation and a constrained current on/off ratio determined by semiconductor bandwidth. These challenges have prompted the search for more advanced materials, with atomic-layer-thick two-dimensional (2D) semiconductors emerging as a potential solution. Following over a decade of research advances, recent developments1,2,3 in wafer-scale growth and device fabrication have led to breakthroughs in 2D semiconductor electronics. However, the level of integration remains constrained to a few hundred transistors. We describe a reduced instruction set computing architecture (RISC-V) microprocessor capable of executing standard 32-bit instructions on 5,900 MoS2 transistors and a complete standard cell library based on 2D semiconductor technology. The library contains 25 types of logic units. In alignment with advances in silicon integrated circuits, we also co-optimized the process flow and design of the 2D logic circuits. Our combined manufacturing and design methodology has overcome the significant challenges associated with wafer-scale integration of 2D circuits and enabled a pioneering prototype of an MoS2 microprocessor that exemplifies the potential of 2D integrated-circuit technology beyond silicon.
Electrical and electronic engineering, Electronic devices
Psilocybin’s lasting action requires pyramidal cell types and 5-HT2A receptors
Original Paper | Neural circuits | 2025-04-01 20:00 EDT
Ling-Xiao Shao, Clara Liao, Pasha A. Davoudian, Neil K. Savalia, Quan Jiang, Cassandra Wojtasiewicz, Diran Tan, Jack D. Nothnagel, Rong-Jian Liu, Samuel C. Woodburn, Olesia M. Bilash, Hail Kim, Alicia Che, Alex C. Kwan
Psilocybin is a serotonergic psychedelic with therapeutic potential for treating mental illnesses1,2,3,4. At the cellular level, psychedelics induce structural neural plasticity5,6, exemplified by the drug-evoked growth and remodelling of dendritic spines in cortical pyramidal cells7,8,9. A key question is how these cellular modifications map onto cell-type-specific circuits to produce the psychedelics’ behavioural actions10. Here we use in vivo optical imaging, chemogenetic perturbation and cell-type-specific electrophysiology to investigate the impact of psilocybin on the two main types of pyramidal cells in the mouse medial frontal cortex. We find that a single dose of psilocybin increases the density of dendritic spines in both the subcortical-projecting, pyramidal tract (PT) and intratelencephalic (IT) cell types. Behaviourally, silencing the PT neurons eliminates psilocybin’s ability to ameliorate stress-related phenotypes, whereas silencing IT neurons has no detectable effect. In PT neurons only, psilocybin boosts synaptic calcium transients and elevates firing rates acutely after administration. Targeted knockout of 5-HT2A receptors abolishes psilocybin’s effects on stress-related behaviour and structural plasticity. Collectively, these results identify that a pyramidal cell type and the 5-HT2A receptor in the medial frontal cortex have essential roles in psilocybin’s long-term drug action.
Neural circuits, Pharmacology, Synaptic plasticity
Clinically relevant clot resolution via a thromboinflammation-on-a-chip
Original Paper | Biomedical engineering | 2025-04-01 20:00 EDT
Yongzhi Qiu, Jessica Lin, Audrey Wang, Zhou Fang, Yumiko Sakurai, Hyoann Choi, Evelyn K. Williams, Elaissa T. Hardy, Kristin Maher, Ahmet F. Coskun, Gary Woods, Wilbur A. Lam
Thromboinflammation occurs in various diseases, leading to life-threatening microvascular occlusion with resulting end-organ failure1,2,3,4. Importantly, how microvascular thromboinflammation resolves remains poorly understood due to the small size-scale of microvasculature and the long duration (weeks to months) of this process. Here we introduce a hydrogel-based thromboinflammation-on-a-chip model with long-term culture capabilities to model microvascular thromboinflammation and monitor clot resolution over clinically and physiologically relevant timescales (up to months). Using this system, we mapped out the distinct temporal phases of clot resolution in microvascular thromboinflammation. Using multiplexed RNA fluorescence in situ hybridization in combination with our thromboinflammation-on-a-chip model, we observed that inflammation shifts the endothelium fibrinolytic balance to favour thrombosis and pinpointed neutrophil elastase as a double-edged sword that induces clot resolution but also tissue damage. We then investigated the mechanisms of potential therapeutic agents that either prevent microvascular thrombosis or accelerate clot resolution. Specifically, we observed that, in thromboinflammation, (1) early tissue plasminogen activator administration within 3 h directly improves endothelial barrier function; (2) prophylactic defibrotide and enoxaparin suppress microvascular thromboinflammation through endothelium-mediated mechanisms; and (3) combining enoxaparin with crizanlizumab reduces microvascular occlusion and protects endothelial function in sickle cell disease. These data introduce a paradigm in investigating the underlying mechanisms of thromboinflammatory clot resolution and conducting drug discovery thereof.
Biomedical engineering, Haematological diseases, Lab-on-a-chip
A neural mechanism for learning from delayed postingestive feedback
Original Paper | Amygdala | 2025-04-01 20:00 EDT
Christopher A. Zimmerman, Scott S. Bolkan, Alejandro Pan-Vazquez, Bichan Wu, Emma F. Keppler, Jordan B. Meares-Garcia, Eartha Mae Guthman, Robert N. Fetcho, Brenna McMannon, Junuk Lee, Austin T. Hoag, Laura A. Lynch, Sanjeev R. Janarthanan, Juan F. López Luna, Adrian G. Bondy, Annegret L. Falkner, Samuel S.-H. Wang, Ilana B. Witten
Animals learn the value of foods on the basis of their postingestive effects and thereby develop aversions to foods that are toxic1,2,3,4,5,6,7,8,9,10 and preferences to those that are nutritious11,12,13. However, it remains unclear how the brain is able to assign credit to flavours experienced during a meal with postingestive feedback signals that can arise after a substantial delay. Here we reveal an unexpected role for the postingestive reactivation of neural flavour representations in this temporal credit-assignment process. To begin, we leverage the fact that mice learn to associate novel14,15, but not familiar, flavours with delayed gastrointestinal malaise signals to investigate how the brain represents flavours that support aversive postingestive learning. Analyses of brain-wide activation patterns reveal that a network of amygdala regions is unique in being preferentially activated by novel flavours across every stage of learning (consumption, delayed malaise and memory retrieval). By combining high-density recordings in the amygdala with optogenetic stimulation of malaise-coding hindbrain neurons, we show that delayed malaise signals selectively reactivate flavour representations in the amygdala from a recent meal. The degree of malaise-driven reactivation of individual neurons predicts the strengthening of flavour responses upon memory retrieval, which in turn leads to stabilization of the population-level representation of the recently consumed flavour. By contrast, flavour representations in the amygdala degrade in the absence of unexpected postingestive consequences. Thus, we demonstrate that postingestive reactivation and plasticity of neural flavour representations may support learning from delayed feedback.
Amygdala, Feeding behaviour, Learning and memory, Neural circuits, Reward
Global impoverishment of natural vegetation revealed by dark diversity
Original Paper | Biodiversity | 2025-04-01 20:00 EDT
Meelis Pärtel, Riin Tamme, Carlos P. Carmona, Kersti Riibak, Mari Moora, Jonathan A. Bennett, Alessandro Chiarucci, Milan Chytrý, Francesco de Bello, Ove Eriksson, Susan Harrison, Robert John Lewis, Angela T. Moles, Maarja Öpik, Jodi N. Price, Vistorina Amputu, Diana Askarizadeh, Zohreh Atashgahi, Isabelle Aubin, Francisco M. Azcárate, Matthew D. Barrett, Maral Bashirzadeh, Zoltán Bátori, Natalie Beenaerts, Kolja Bergholz, Kristine Birkeli, Idoia Biurrun, José M. Blanco-Moreno, Kathryn J. Bloodworth, Laura Boisvert-Marsh, Bazartseren Boldgiv, Pedro H. S. Brancalion, Francis Q. Brearley, Charlotte Brown, C. Guillermo Bueno, Gabriella Buffa, James F. Cahill, Juan A. Campos, Giacomo Cangelmi, Michele Carbognani, Christopher Carcaillet, Bruno E. L. Cerabolini, Richard Chevalier, Jan S. Clavel, José M. Costa, Sara A. O. Cousins, Jan Čuda, Mariana Dairel, Michele Dalle Fratte, Alena Danilova, John Davison, Balázs Deák, Silvia Del Vecchio, Iwona Dembicz, Jürgen Dengler, Jiri Dolezal, Xavier Domene, Miroslav Dvorsky, Hamid Ejtehadi, Lucas Enrico, Dmitrii Epikhin, Anu Eskelinen, Franz Essl, Gaohua Fan, Edy Fantinato, Fatih Fazlioglu, Eduardo Fernández-Pascual, Arianna Ferrara, Alessandra Fidelis, Markus Fischer, Maren Flagmeier, T’ai G. W. Forte, Lauchlan H. Fraser, Junichi Fujinuma, Fernando F. Furquim, Berle Garris, Heath W. Garris, Melisa A. Giorgis, Gianpietro Giusso del Galdo, Ana González-Robles, Megan K. Good, Moisès Guardiola, Riccardo Guarino, Irene Guerrero, Joannès Guillemot, Behlül Güler, Yinjie Guo, Stef Haesen, Martin Hejda, Ruben H. Heleno, Toke T. Høye, Richard Hrivnák, Yingxin Huang, John T. Hunter, Dmytro Iakushenko, Ricardo Ibáñez, Nele Ingerpuu, Severin D. H. Irl, Eva Janíková, Florian Jansen, Florian Jeltsch, Anke Jentsch, Borja Jiménez-Alfaro, Madli Jõks, Mohammad H. Jouri, Sahar Karami, Negin Katal, András Kelemen, Bulat I. Khairullin, Anzar A. Khuroo, Kimberly J. Komatsu, Marie Konečná, Ene Kook, Lotte Korell, Natalia Koroleva, Kirill A. Korznikov, Maria V. Kozhevnikova, Łukasz Kozub, Lauri Laanisto, Helena Lager, Vojtech Lanta, Romina G. Lasagno, Jonas J. Lembrechts, Liping Li, Aleš Lisner, Houjia Liu, Kun Liu, Xuhe Liu, Manuel Esteban Lucas-Borja, Kristin Ludewig, Katalin Lukács, Jona Luther-Mosebach, Petr Macek, Michela Marignani, Richard Michalet, Tamás Miglécz, Jesper Erenskjold Moeslund, Karlien Moeys, Daniel Montesinos, Eduardo Moreno-Jiménez, Ivan Moysiyenko, Ladislav Mucina, Miriam Muñoz-Rojas, Raytha A. Murillo, Sylvia M. Nambahu, Lena Neuenkamp, Signe Normand, Arkadiusz Nowak, Paloma Nuche, Tatjana Oja, Vladimir G. Onipchenko, Kalina L. Pachedjieva, Bruno Paganeli, Begoña Peco, Ana M. L. Peralta, Aaron Pérez-Haase, Pablo L. Peri, Alessandro Petraglia, Gwendolyn Peyre, Pedro Antonio Plaza-Álvarez, Jan Plue, Honor C. Prentice, Vadim E. Prokhorov, Dajana Radujković, Soroor Rahmanian, Triin Reitalu, Michael Ristow, Agnès A. Robin, Ana Belén Robles, Daniel A. Rodríguez Ginart, Raúl Román, Ruben E. Roos, Leonardo Rosati, Jiří Sádlo, Karina Salimbayeva, Rut Sánchez de Dios, Khaliun Sanchir, Cornelia Sattler, John D. Scasta, Ute Schmiedel, Julian Schrader, Nick L. Schultz, Giacomo Sellan, Josep M. Serra-Diaz, Giulia Silan, Hana Skálová, Nadiia Skobel, Judit Sonkoly, Kateřina Štajerová, Ivana Svitková, Sebastian Świerszcz, Andrew J. Tanentzap, Fallon M. Tanentzap, Rubén Tarifa, Pablo Tejero, Dzhamal K. Tekeev, Michael Tholin, Ruben S. Thormodsæter, Yichen Tian, Alla Tokaryuk, Csaba Tölgyesi, Marcello Tomaselli, Enrico Tordoni, Péter Török, Béla Tóthmérész, Aurèle Toussaint, Blaise Touzard, Diego P. F. Trindade, James L. Tsakalos, Sevda Türkiş, Enrique Valencia, Mercedes Valerio, Orsolya Valkó, Koenraad Van Meerbeek, Vigdis Vandvik, Jesus Villellas, Risto Virtanen, Michaela Vítková, Martin Vojík, Andreas von Hessberg, Jonathan von Oppen, Viktoria Wagner, Ji-Zhong Wan, Chun-Jing Wang, Sajad A. Wani, Lina Weiss, Tricia Wevill, Sa Xiao, Oscar Zárate Martínez, Martin Zobel
Anthropogenic biodiversity decline threatens the functioning of ecosystems and the many benefits they provide to humanity1. As well as causing species losses in directly affected locations, human influence might also reduce biodiversity in relatively unmodified vegetation if far-reaching anthropogenic effects trigger local extinctions and hinder recolonization. Here we show that local plant diversity is globally negatively related to the level of anthropogenic activity in the surrounding region. Impoverishment of natural vegetation was evident only when we considered community completeness: the proportion of all suitable species in the region that are present at a site. To estimate community completeness, we compared the number of recorded species with the dark diversity–ecologically suitable species that are absent from a site but present in the surrounding region2. In the sampled regions with a minimal human footprint index, an average of 35% of suitable plant species were present locally, compared with less than 20% in highly affected regions. Besides having the potential to uncover overlooked threats to biodiversity, dark diversity also provides guidance for nature conservation. Species in the dark diversity remain regionally present, and their local populations might be restored through measures that improve connectivity between natural vegetation fragments and reduce threats to population persistence.
Biodiversity, Conservation biology, Macroecology
Haploid facultative parthenogenesis in sunflower sexual reproduction
Original Paper | Agricultural genetics | 2025-04-01 20:00 EDT
Jian Lv, Dawei Liang, Eric Bumann, Virginie Mirleau Thebaud, Huaibing Jin, Changbao Li, Clemence Paris, Yinghui Dan, Chao Li, Ruijie Cui, Xianxia Chen, David Szwerdszarf, Peter Wittich, Bobby Clegg, Agustin Tassara, Hongmei Dan, Xiaolong Tian, Zhiqiang Liu, Wen Cai, Bin Sun, Jared Carter, Paul Drayton, Federico Bock, Timothy Kelliher
Flowering plant sexual reproduction requires double fertilization, yielding embryo and endosperm seed compartments: the latter supports embryo growth and seed germination. In an experiment to generate haploid embryos through inhibition of pollen phospholipase activity in sunflower (Helianthus annus), we serendipitously discovered that emasculated sunflowers spontaneously form parthenogenic haploid seed. Exploration of genetic, chemical and environmental factors demonstrated that a specific genotype background enabled high parthenogenesis and that full spectrum high-intensity light supplementation boosted parthenogenesis, yielding hundreds of haploid seeds per head. Induction of doubled haploid plants can greatly accelerate plant breeding efficiency; however, despite successful engineering of haploid induction in many crops, few reported systems are commercially scalable1. Here we report efficient methods of chemical emasculation and genome doubling to produce fertile plants and enable a scalable sunflower doubled haploid system.
Agricultural genetics, Embryonic induction, Fertilization, Plant breeding
The RAD52 double-ring remodels replication forks restricting fork reversal
Original Paper | Cryoelectron microscopy | 2025-04-01 20:00 EDT
Masayoshi Honda, Mortezaali Razzaghi, Paras Gaur, Eva Malacaria, Giorgia Marozzi, Ludovica Di Biagi, Francesca Antonella Aiello, Emeleeta A. Paintsil, Andrew J. Stanfield, Bailey J. Deppe, Lokesh Gakhar, Nicholas J. Schnicker, M. Ashley Spies, Pietro Pichierri, Maria Spies
Human RAD52 is a multifunctional DNA repair protein involved in several cellular events that support genome stability, including protection of stalled DNA replication forks from excessive degradation1,2,3,4. In its gatekeeper role, RAD52 binds to and stabilizes stalled replication forks during replication stress, protecting them from reversal by SMARCAL1 motor3. The structural and molecular mechanism of the RAD52-mediated fork protection remains elusive. Here, using P1 nuclease sensitivity, biochemical and single-molecule analyses, we show that RAD52 dynamically remodels replication forks through its strand exchange activity. The presence of the single-stranded DNA binding protein RPA at the fork modulates the kinetics of the strand exchange without impeding the reaction outcome. Mass photometry and single-particle cryo-electron microscopy show that the replication fork promotes a unique nucleoprotein structure containing head-to-head arrangement of two undecameric RAD52 rings with an extended positively charged surface that accommodates all three arms of the replication fork. We propose that the formation and continuity of this surface is important for the strand exchange reaction and for competition with SMARCAL1.
Cryoelectron microscopy, DNA, DNA-binding proteins, Single-molecule biophysics
Acoustic modes in M67 cluster stars trace deepening convective envelopes
Original Paper | Stars | 2025-04-01 20:00 EDT
Claudia Reyes, Dennis Stello, Joel Ong, Christopher Lindsay, Marc Hon, Timothy R. Bedding
Acoustic oscillations in stars are sensitive to stellar interiors1. Frequency differences between overtone modes–large separations–probe stellar density2, whereas differences between low-degree modes–small separations–probe the sound-speed gradient in the energy-generating core of main-sequence Sun-like stars3, and hence their ages. At later phases of stellar evolution, characterized by inert cores, small separations are believed to lose much of their power to probe deep interiors and become proportional to large separations4,5. Here we present evidence of a rapidly evolving convective zone as stars evolve from the subgiant phase into red giants. By measuring acoustic oscillations in 27 stars from the open cluster M67, we observe deviations of proportionality between small and large separations, which are caused by the influence of the bottom of the convective envelope. These deviations become apparent as the convective envelope penetrates deep into the star during subgiant and red giant evolutions, eventually entering an ultradeep regime that leads to the red-giant-branch luminosity bump. The tight sequence of cluster stars, free of large spreads in ages and fundamental properties, is essential for revealing the connection between the observed small separations and the chemical discontinuities occurring at the bottom of the convective envelope. We use this sequence to show that combining large and small separations can improve estimations of the masses and ages of field stars well after the main sequence.
Stars, Stellar evolution
Ancient DNA from the Green Sahara reveals ancestral North African lineage
Original Paper | Anthropology | 2025-04-01 20:00 EDT
Nada Salem, Marieke S. van de Loosdrecht, Arev Pelin Sümer, Stefania Vai, Alexander Hübner, Benjamin Peter, Raffaela A. Bianco, Martina Lari, Alessandra Modi, Mohamed Faraj Mohamed Al-Faloos, Mustafa Turjman, Abdeljalil Bouzouggar, Mary Anne Tafuri, Giorgio Manzi, Rocco Rotunno, Kay Prüfer, Harald Ringbauer, David Caramelli, Savino di Lernia, Johannes Krause
Although it is one of the most arid regions today, the Sahara Desert was a green savannah during the African Humid Period (AHP) between 14,500 and 5,000 years before present, with water bodies promoting human occupation and the spread of pastoralism in the middle Holocene epoch1. DNA rarely preserves well in this region, limiting knowledge of the Sahara’s genetic history and demographic past. Here we report ancient genomic data from the Central Sahara, obtained from two approximately 7,000-year-old Pastoral Neolithic female individuals buried in the Takarkori rock shelter in southwestern Libya. The majority of Takarkori individuals’ ancestry stems from a previously unknown North African genetic lineage that diverged from sub-Saharan African lineages around the same time as present-day humans outside Africa and remained isolated throughout most of its existence. Both Takarkori individuals are closely related to ancestry first documented in 15,000-year-old foragers from Taforalt Cave, Morocco2, associated with the Iberomaurusian lithic industry and predating the AHP. Takarkori and Iberomaurusian-associated individuals are equally distantly related to sub-Saharan lineages, suggesting limited gene flow from sub-Saharan to Northern Africa during the AHP. In contrast to Taforalt individuals, who have half the Neanderthal admixture of non-Africans, Takarkori shows ten times less Neanderthal ancestry than Levantine farmers, yet significantly more than contemporary sub-Saharan genomes. Our findings suggest that pastoralism spread through cultural diffusion into a deeply divergent, isolated North African lineage that had probably been widespread in Northern Africa during the late Pleistocene epoch.
Anthropology, Archaeology, Evolutionary genetics, Genomics, Population genetics
Nature Materials
Giant nonlinear Raman responses from organic semiconductors
Original Paper | Molecular electronics | 2025-04-01 20:00 EDT
Yi Jiang, He Lin, Jin-Qiang Pan, Jia-Ling Zhang, Hoi Lam Tam, King Fai Li, Qi Wei, Sheung Mei Ng, Chee Leung Mak, Yong Jie Huang, Yang Wang, Zhan-Bo Jia, Xiang-Chun Li, Luying Yi, Ifor D. W. Samuel, Kok Wai Cheah, Xiaogang Liu, Wei Huang, Wen-Yong Lai
Organic semiconductors exhibit unique semiconducting behaviour due to π-electron delocalization along their molecular chains, making them attractive for various optoelectronic applications. However, their low optical damage thresholds have limited their use in nonlinear optics, particularly in stimulated Raman scattering. Here we demonstrate a general method to significantly amplify molecular vibrations in organic semiconductors by utilizing spectrally tailored gain from stimulated emission, bypassing the necessity for traditional optical cavities. This method achieves Raman thresholds as low as ~10-50 μJ cm-2 or ~2-10 kW cm-2, outperforming current Raman lasers by four orders of magnitude. The resulting nonlinear Raman response leads to cascaded Raman emission characterized by pump-dependent emission efficiency, a nonlinearity factor of 3.8, a signal-to-noise ratio of 30.9 dB and a bandwidth of 110 nm. Our study opens exciting prospects for the development of compact, efficient Raman amplifiers and lasers, leveraging the unique properties of organic semiconductors for advanced photonic applications, including high-sensitivity spectroscopy and versatile frequency conversion technologies.
Molecular electronics, Nonlinear optics, Organic molecules in materials science, Polymers
Microstructure engineering in diamond-based materials
Review Paper | Ceramics | 2025-04-01 20:00 EDT
Anmin Nie, Zhisheng Zhao, Bo Xu, Yongjun Tian
Diamond possesses a suite of extraordinary properties, including unparalleled hardness, excellent thermal conductivity, a wide bandgap and optical transparency. These features render it essential for a broad spectrum of scientific and industrial applications. However, the inherent brittleness and limited toughness of diamond have posed substantial barriers to broader technological integration. Recent advances have demonstrated that engineered structural configurations–including nanotwinned diamond architectures, hierarchically structured nanotwinned diamond composites, graphite-diamond hybrids, diamond-graphene composites and amorphous diamond phases–can overcome these conventional limitations, exhibiting superior mechanical and physical properties. This Review examines the latest developments in diamond and its derivative materials, focusing on microstructural design strategies, phase transition mechanisms, opportunities to enhance properties and emergent phenomena. We also outline promising research directions and potential applications for diamond-based materials, advancing the frontiers of diamond-based technologies.
Ceramics, Mechanical properties
Nature Physics
Coherent control of a superconducting qubit using light
Original Paper | Microwave photonics | 2025-04-01 20:00 EDT
Hana K. Warner, Jeffrey Holzgrafe, Beatriz Yankelevich, David Barton, Stefano Poletto, C. J. Xin, Neil Sinclair, Di Zhu, Eyob Sete, Brandon Langley, Emma Batson, Marco Colangelo, Amirhassan Shams-Ansari, Graham Joe, Karl K. Berggren, Liang Jiang, Matthew J. Reagor, Marko Lončar
Quantum communications technologies require a network of quantum processors connected with low-loss and low-noise communication channels capable of distributing entangled states. Superconducting microwave qubits operating in cryogenic environments have emerged as promising candidates for quantum processor nodes. However, scaling these systems is challenging because they require bulky microwave components with high thermal loads that can quickly overwhelm the cooling power of a dilution refrigerator. Telecommunication frequency optical signals, however, can be fabricated in significantly smaller form factors to avoid challenges caused by high signal loss, noise sensitivity and thermal loads due to their high carrier frequency and propagation in silica optical fibres. Transduction of information by means of coherent links between optical and microwave frequencies is therefore critical to leverage the advantages of optics for superconducting microwave qubits, while also enabling superconducting processors to be linked with low-loss optical interconnects. Here, we demonstrate coherent optical control of a superconducting qubit. We achieve this by developing a microwave-optical quantum transducer that operates with up to 1.18% conversion efficiency with low added microwave noise, and we demonstrate optically driven Rabi oscillations in a superconducting qubit.
Microwave photonics, Optoelectronic devices and components, Photonic devices, Qubits, Superconducting devices
Physical Review Letters
Measurements of Pion and Muon Nuclear Capture at Rest on Argon in the LArIAT Experiment
Research article | Muons | 2025-04-01 06:00 EDT
M. A. Hernandez-Morquecho, R. Acciarri, J. Asaadi, M. Backfish, W. Badgett, V. Basque, F. d. M. Blaszczyk, W. Foreman, R. A. Gomes, E. Gramellini, J. Ho, E. Kearns, E. Kemp, T. Kobilarcik, M. King, B. R. Littlejohn, X. Luo, A. Marchionni, C. A. Moura, J. L. Raaf, D. W. Schmitz, M. Soderberg, J. M. St. John, A. M. Szelc, and T. Yang (LArIAT Collaboration)
We report the measurement of the final-state products of negative pion and muon nuclear capture at rest on argon by the LArIAT experiment at the Fermilab Test Beam Facility. We measure a population of isolated MeV-scale energy depositions, or blips, in 296 LArIAT events containing tracks from stopping low-momentum pions and muons. The average numbers of visible blips are measured to be $0.74\pm{}0.19$ and $1.86\pm{}0.17$ near muon and pion track endpoints, respectively. The $3.6\sigma $ statistically significant difference in blip content between muons and pions provides the first demonstration of a new method of pion-muon discrimination in neutrino liquid argon time projection chamber experiments. LArIAT Monte Carlo simulations predict substantially higher average blip counts for negative muon ($1.22\pm{}0.08$) and pion ($2.34\pm{}0.09$) nuclear captures. We attribute this difference to geant4’s inaccurate simulation of the nuclear capture process.
Phys. Rev. Lett. 134, 131801 (2025)
Muons, Neutrinos, Monte Carlo methods, Particle data analysis
Why Charged Drops Do Not Splash
Research article | Drop & bubble phenomena | 2025-04-01 06:00 EDT
Fanfei Yu, Aaron D. Ratschow, Ran Tao, Xiaomei Li, Yuankai Jin, Jinpei Wang, and Zuankai Wang
The messy breakup of a liquid droplet that occurs when it hits a surface can be suppressed by giving the droplet an electrical charge.
Phys. Rev. Lett. 134, 134001 (2025)
Drop & bubble phenomena, Wetting, Interfaces, Liquid-solid interfaces
Shear and Bulk Viscosities of Water up to 1.6 GPa and Anomaly in the Structural Relaxation Time
Research article | Elastic modulus | 2025-04-01 06:00 EDT
Jan Eichler, Johannes Stefanski, José Martin Roca, Isabelle Daniel, Bruno Issenmann, Chantal Valeriani, and Frédéric Caupin
Deep in Earth’s crust, pressure exceeds 1000 times the atmospheric pressure. Water still flows under these conditions, but experiences dramatic changes in structure and fluidity. Using combined dynamic and inelastic light scattering techniques, we simultaneously measure the shear and bulk viscosities of water as a function of pressure. The former increases faster than the latter, so that their ratio shows a twofold decrease from 0 to 1.6 GPa; we confirm this trend with simulations. We analyze our results in terms of the structural relaxation time $\tau $. Contrary to other liquids, pressure initially accelerates relaxation in water. Our measurements reveal that $\tau $ reaches a minimum close to 1 ps around 0.5 GPa. We interpret $\tau $ as the equilibration time of hydrogen bonds and propose that the minimum in $\tau $ arises from a structural anomaly that allows fastest interconversion between local structures in water and generates a cascade of thermodynamic and dynamic anomalies.
Phys. Rev. Lett. 134, 134101 (2025)
Elastic modulus, High-pressure studies, Ultrasound attenuation, Water, Viscosity, Brillouin scattering & spectroscopy, Light scattering, Molecular dynamics
Prediction of Room Temperature Electric Field Reversal of Magnetization in the Family of ${A}{4}{B}{3}{\mathrm{O}}_{9}$ Layered Oxides
Research article | Ferroelectricity | 2025-04-01 06:00 EDT
Urmimala Dey, Emma E. McCabe, Jorge Íñiguez-González, and Nicholas C. Bristowe
The promise of a strong magnetoelectric coupling in a multiferroic material is not only of fundamental interest, but also forms the basis of next generation memory devices where the direction of magnetization can be reversed by an external electric field. Using group-theory led first-principles calculations, we have identified a hitherto unknown polar phase of the ${A}{4}{B}{3}{\mathrm{O}}{9}$ layered oxides, where the polar mode couples to the magnetic modes through a rare $\mathrm{\Gamma }$-point magnetoelectric-multiferroic coupling scheme such that the net magnetization can be directly reversed by an electric field switching of the polar mode. Furthermore, in agreement with previous experimental observations, we predict room temperature magnetism in ${A}{4}{B}{3}{\mathrm{O}}{9}$ oxides that indicates the promising practical applications of these compounds in the next generation memory devices.
Phys. Rev. Lett. 134, 136801 (2025)
Ferroelectricity, First-principles calculations, Landau theory, Magnetic order, Magnetism, Order parameters, Phonons, Spin-orbit coupling
High Reconstructability of Degree-Heterogeneous Networks
Research article | Network structure | 2025-04-01 06:00 EDT
Jia-Jie Qin and Gang Yan
The fidelity of a complex system’s representation as a network model depends on the diversity of its interconnections.
Phys. Rev. Lett. 134, 137402 (2025)
Network structure, Scale free & inhomogeneous networks, Network inference
Erratum: Beam Energy Dependence of Fifth- and Sixth-Order Net-Proton Number Fluctuations in $\mathrm{Au}+\mathrm{Au}$ Collisions at RHIC [Phys. Rev. Lett. 130, 082301 (2023)]
Correction | | 2025-04-01 06:00 EDT
B. E. Aboona et al. (STAR Collaboration)
et al.
Phys. Rev. Lett. 134, 139901 (2025)
Erratum: Measurement of the Sixth-Order Cumulant of Net-Proton Multiplicity Distributions in $\mathrm{Au}+\mathrm{Au}$ Collisions at $\sqrt{ {s}_{\mathrm{NN}}}=27$, 54.4, and 200 GeV at RHIC [Phys. Rev. Lett. 127, 262301 (2021)]
Correction | | 2025-04-01 06:00 EDT
M. S. Abdallah et al. (STAR Collaboration)
et al.
Phys. Rev. Lett. 134, 139903 (2025)
Physical Review X
Revealing the Electron-Spin Fluctuation Coupling by Photoemission in ${\mathrm{CaKFe}}{4}{\mathrm{As}}{4}$
Research article | Electrical properties | 2025-04-01 06:00 EDT
Peng Li, Yuzhe Wang, Yabin Liu, Jianghao Yao, Zhisheng Zhao, Zhengtai Liu, Dawei Shen, Huiqian Luo, Guanghan Cao, Juan Jiang, and Donglai Feng
High-resolution spectroscopy of CaKFe₄As₄ reveals that spin fluctuations, not phonons, drive its superconductivity, a result that lays a path for unifying theories of iron-based superconductors.
Phys. Rev. X 15, 021001 (2025)
Electrical properties, Electronic structure, Superconductivity, Photoemission spectroscopy
ac Stark Spectroscopy of Interactions between Moiré Excitons and Polarons
Research article | Excitons | 2025-04-01 06:00 EDT
B. Evrard, H. S. Adlong, A. A. Ghita, T. Uto, L. Ciorciaro, K. Watanabe, T. Taniguchi, M. Kroner, and A. İmamoğlu
Nonlinear optical measurements reveal drastic modification of excitonic interactions in semiconductor moiré materials. In stark contrast to monolayers, the interaction between excitons dressed by moiré localized electrons is suppressed.
Phys. Rev. X 15, 021002 (2025)
Excitons, Polarons, Semiconductor quantum optics, Stark effect, Transition metal dichalcogenides, Twisted heterostructures, Two-dimensional electron gas, Two-dimensional electron system, Ultrafast pump-probe spectroscopy
arXiv
Probing electronic transitions and defect-induced Urbach tail bands in functional perovskite oxides using diffuse reflectance
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-04-02 20:00 EDT
Ramachandran Balakrishnan, Priyambada Sahoo, Balamurugan Karuppannan, Ambesh Dixit
We conducted a detailed study of electronic transitions and defects induced Urbach tail bands in various functional perovskite oxides (V2O5, BaSnO3, PbZr0.52Ti0.48O3, BiMnO3, and BiFeO3) using diffuse reflectance spectroscopy (DRS). We analyzed their DRS spectra using the Kubelka-Munk (KM) function, the Tauc plot, and the first derivative of the reflectance for a comparative study. BiMnO3 exhibits an electronic transition with indirect band gap energy, Eg = 0.92 eV. In contrast, all other functional perovskite oxides, namely bulk V2O5, BaSnO3, PbZr0.52Ti0.48O3, and BiFeO3, show direct band gap interband transitions, with Eg values of 2.27, 3.25, 3.10, and 2.48 eV, respectively. The estimated Urbach energy (EU) values related to the induced defects in these direct band gap functional oxides are approximately 0.24, 0.38, 0.25, and 0.48 eV, respectively. Moreover, a reduction in the band gap energy of multiferroic BiFeO3 was observed due to induced chemical pressure from (Ba, Ca) doping and a decrease in particle size. Importantly, the evaluated band gap and Urbach energies of the functional perovskite oxide materials obtained from the analyses of the first derivative of reflectance and the Tauc plot method align remarkably well with the values deduced using the Kubelka-Munk function theory. Effectively, we propose a comprehensive electronic band structure for the multiferroic BiFeO3, an important material for optoelectronic applications such as photovoltaic, photocatalytic, and photoferroelectric devices.
Materials Science (cond-mat.mtrl-sci)
41 pages, 17 figures, Submitted for Publication in a Journal (Journal of Physics D: Applied Physics)
Fractional diffusion without disorder in two dimensions
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-04-02 20:00 EDT
Nilotpal Chakraborty, Markus Heyl, Roderich Moessner
We analyse how simple local constraints in two dimensions lead a defect to exhibit robust, non-transient, and tunable, subdiffusion. We uncover a rich dynamical phenomenology realised in ice- and dimer-type models. On the microscopic scale the path of a single defect exhibits anomalously long retractions, amounting to dynamical caging in a continuous-time random-walk framework, culminating in an effective fractional diffusion equation. Mapping to a height field yields an effective random walk subject to an emergent (entropic) logarithmic potential, whose strength is tunable, related to the exponent of algebraic ground-state correlations. The defect’s path, viewed as non-equilibrium growth process, yields a frontier of fractal dimension of $ 5/4$ , the value for a loop-erased random walk, rather than $ 4/3$ for simple and self-avoiding random walks. Such frustration/constraint-induced subdiffusion is expected to be relevant to platforms such as artificial spin ice and quantum simulators aiming to realize discrete link models and emergent gauge theories.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Disordered Systems and Neural Networks (cond-mat.dis-nn), Statistical Mechanics (cond-mat.stat-mech)
5+2 pages; 5 figures. Comments welcome
Spin order, spin excitations, and RIXS spectra of spin-1/2 tetramer chains
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-04-02 20:00 EDT
Junli Li, Jun-Qing Cheng, Trinanjan Datta, Dao-Xin Yao
We investigate the spin dynamics of a 1D spin-1/2 Heisenberg tetramer chain. Employing a combination of Density Matrix Renormalization Group, quantum renormalization group, and perturbation theory techniques, we compute the energy levels and the quantum phase diagram, analyze the phase transitions, and evaluate the $ L$ and $ K$ -edge resonant inelastic x-ray scattering (RIXS) spectrum of fractionalized and collective (single and multi-particle) excitations. Our calculations suggest that the chain can transition between a hidden $ Z_2\times Z_2$ discrete symmetry preserving tetramer phase and a Haldane phase with non-vanishing string order that breaks the hidden symmetry. These two gapped phases are intervened by an intermediate deconfined quantum critical state comprising of free spins and three-site doublets, which is a gapless critical phase with deconfined spinons. We find that the tetramer chain can support fractionalized (spinon) and collective (triplon and quinton) excitations. In the ferromagnetic intra-tetramer limit, the chain can support a quinton excitation which has a five-fold degenerate excited state. String order parameter calculations suggest CuInVO$ _5$ to be in a Haldane-like phase whose $ L$ -edge RIXS spectrum can support observable triplon and quinton excitations. We also identify possible two-particle excitations (two-singlon, two-triplon, triplon-quinton, and two-quinton excitations) resulting from the double spin-flip effect in the $ K$ -edge RIXS spectrum.
Strongly Correlated Electrons (cond-mat.str-el), Materials Science (cond-mat.mtrl-sci)
13 pages, 7 figures
Antiferro octupolar order in the 5d$^1$ double perovskite Sr$_2$MgReO$_6$ and its spectroscopic signatures
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-04-02 20:00 EDT
Dario Fiore Mosca, Leonid V. Pourovskii
“Hidden”-order phases with high-rank multipolar order parameters have been recently detected in several cubic double perovskites of 5$ d$ transition metals. Here, by constructing and solving an ab initio low-energy Hamiltonian, we show that an antiferroic order of magnetic octupoles also forms in the tetragonal 5d$ ^1$ double perovskite Sr$ _2$ MgReO$ _6$ . The low-temperature order in this material is determined by a tetragonal crystal field dominating over exchange interactions. This results in a well isolated crystal-field doublet ground state hosting octupolar low-energy degrees of freedom. Very weak dipole moments entangled with the primary octupole order parameters are induced by admixture of the excited $ j1/2$ spin-orbit multiplet. We show that the octupolar order leads to characteristic quasi-gapless magnetic excitation spectra as well as to the intensity of superstructural neutron diffraction reflexes peaking at large scattering momenta.
Strongly Correlated Electrons (cond-mat.str-el), Materials Science (cond-mat.mtrl-sci)
7 + 7 pages; 3 + 4 figures
Ultrafast Spontaneous Exciton Dissociation via Phonon Emission in BiVO$_4$
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-04-02 20:00 EDT
Stephen E. Gant, Antonios M. Alvertis, Christopher J. N. Coveney, Jonah B. Haber, Marina R. Filip, Jeffrey B. Neaton
Monoclinic bismuth vanadate (m-BiVO$ _4$ ) is a promising indirect band gap semiconductor for photoelectrochemical water splitting, yet the characteristics of its low-lying photoexcitations, or excitons, remain poorly understood. Here, we use an ab initio Bethe-Salpeter equation approach that incorporates phonon screening to compute the nature and lifetimes of the low-lying excitons of m-BiVO$ _4$ . Our calculations indicate that at 0 K, the lowest-lying exciton energy exceeds the indirect band gap, enabling spontaneous dissociation into free carriers via phonon emission within picoseconds. At 300 K, both phonon emission and absorption effects reduce this timescale to only a few femtoseconds. Phonon screening also greatly reduces the binding energy of the lowest-lying exciton, leading to an optical absorption spectrum that better reproduces experimental measurements. Overall, our findings establish the general conditions under which phonon emission-driven exciton dissociation can occur in indirect gap semiconductors, and they emphasize the critical role phonon screening can play in predictive calculations of photophysical properties of complex materials.
Materials Science (cond-mat.mtrl-sci)
Dynamical Generation of Higher-order Spin-Orbit Couplings, Topology and Persistent Spin Texture in Light-Irradiated Altermagnets
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-04-02 20:00 EDT
Sayed Ali Akbar Ghorashi, Qiang Li
Altermagnets have been identified as the third category of magnetic materials, exhibiting momentum-dependent spin splitting characterized by even powers of momentum. In this study, we show that when subjected to elliptically polarized light, these materials serve as an exemplary framework for the dynamic generation of topological bands featuring higher-order spin-orbit coupling (SOC). Notably, while the generated Zeeman field remains invariant to the particular altermagnetic ordering, the induced higher-order SOCs are related to the magnitude and symmetry of the altermagnetic order. Specifically, we show that an altermagnet exhibiting $ k^n$ -spin splitting can generate spin-orbit couplings up to $ k^{n-1}$ . In the limit of circularly polarized light, the only correction is $ k^{n-1}$ , with all lower-order contributions being nullified. Interestingly, light-induced SOCs significantly impact the low-energy band topology, where their Chern numbers change by $ \Delta C =\pm 1,2,3$ for $ d,g,f$ -wave altermagnets. Finally, we find a critical field in which a persistent spin texture is realized, a highly desirable state with predicted infinite spin lifetime. Our work showcases light as a powerful, controllable tool for engineering complex and exciting phenomena in altermagnets.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci), Strongly Correlated Electrons (cond-mat.str-el)
Submitted
$\textit{PY-BerryAHC}$: An $\textit{ab-initio}$ python 3 code to calculate Berry Curvature dependent Anomalous Hall Conductivity in any material
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-04-02 20:00 EDT
Vivek Pandey, Sudhir K. Pandey
The anomalous Hall conductivity (AHC) in materials has long been a topic of debate. Studies reveal that AHC originates from the Berry curvature ($ \boldsymbol\Omega$ ) of Bloch states. Accurate computation of AHC is crucial for predicting material properties and guiding experimental studies in topological and spintronic applications. Traditional approaches often rely on wannier interpolation, which can introduce inaccuracies and computational overhead. Also, reliability of the wannierization technique becomes questionable when the bands are highly entangled and dispersive. This demands the calculation of AHC using the $ \textit{first-principle}$ approach. Here, we present $ \textit{PY-BerryAHC}$ , a Python 3 based code that directly computes $ \boldsymbol\Omega$ and AHC using WIEN2k output. Since, WIEN2k employs an all-electron full-potential linearized augmented plane wave method, $ \textit{PY-BerryAHC}$ provides highly accurate AHC results. The code efficiently handles large $ \textbf{k}$ -grids by parallelizing $ \boldsymbol\Omega$ computations over $ \textbf{k}$ -points. Also, it stores band-resolved $ \boldsymbol\Omega$ in a binary file, thereby greatly reducing the required storage memory and allowing fast post-processing to compute AHC. $ \textit{PY-BerryAHC}$ has been validated on well-known materials exhibiting AHC. These include- Fe, Fe$ _3$ Ge & Co$ 2$ FeAl. At 300 K, the calculated magnitude of $ \sigma{xy}$ for Fe & Fe$ _3$ Ge is found to be 744 $ S/cm$ & 311 $ S/cm$ , respectively. For Co$ 2$ FeAl, the magnitude of $ \sigma{xy}$ is obtained to be $ \sim$ 56 $ S/cm$ and is found to be constant with the change in temperature from 0-300 K. These results are in good agreement with previously reported theoretical and experimental data. This ensures the accuracy, reliability and efficiency of the code. The code is also provided with a post-processing tool to visualize $ \boldsymbol\Omega$ .
Strongly Correlated Electrons (cond-mat.str-el)
Topological Symmetry Breaking in Antagonistic Dynamics
New Submission | Disordered Systems and Neural Networks (cond-mat.dis-nn) | 2025-04-02 20:00 EDT
Giulio Iannelli, Pablo Villegas, Tommaso Gili, Andrea Gabrielli
A dynamic concordia discors, a finely tuned equilibrium between opposing forces, is hypothesized to drive historical transformations. Similarly, a precise interplay of excitation and inhibition, the 80:20 ratio, is at the basis of the normal functionality of neural systems. In artificial neural networks, reinforcement learning allows for fine-tuning internal signed connections, optimizing adaptive responses to complex stimuli, and ensuring robust performance. At present, engineered structures of competing components are, however, largely unexplored, particularly because their emergent phases are closely linked with frustration mechanisms in the hosting network. In this context, the spin glass theory has shown how an apparently uncontrollable non-ergodic chaotic behavior arises from the complex interplay of competing interactions and frustration among units, leading to multiple metastable states preventing the system from exploring all accessible configurations over time. Here, we tackle the problem of disentangling topology and dynamics in systems with antagonistic interactions. We make use of the signed Laplacian operator to demonstrate how fundamental topological defects in lattices and networks percolate, shaping the geometrical arena and complex energy landscape of the system. This unveils novel, highly robust multistable phases and establishes deep connections with spin glasses when thermal noise is considered, providing a natural topological and algebraic description of their still-unknown set of pure states at zero temperature.
Disordered Systems and Neural Networks (cond-mat.dis-nn), Statistical Mechanics (cond-mat.stat-mech), Physics and Society (physics.soc-ph)
9 Pages, 4 Figures and Supplementary Information
Emergence of universality in transport of noisy free fermions
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-04-02 20:00 EDT
João Costa, Pedro Ribeiro, Andrea De Luca
We analyze the effects of various forms of noise on one-dimensional systems of non-interacting fermions. In the strong noise limit, we demonstrate, under mild assumptions, that the statistics of the fermionic correlation matrix in the thermodynamic limit follow a universal form described by the recently introduced quantum simple symmetric exclusion process (Q-SSEP). For charge transport, we show that Q-SSEP, along with all models in its universality class, shares the same large deviation function for the transferred charge as the classical SSEP model. The method we introduce to derive this result relies on a gauge-like invariance associated with the choice of the bond where the current is measured. This approach enables the explicit calculation of the cumulant generating function for both Q-SSEP and SSEP and establishes an exact correspondence between them. These analytical findings are validated by extensive numerical simulations. Our results establish that a wide range of noisy free-fermionic models share the same Q-SSEP universality class and show that their transport properties are essentially classical.
Statistical Mechanics (cond-mat.stat-mech)
Surface Sensitive Raman Response of Metal-Supported Monolayer MoS$_2$
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-04-02 20:00 EDT
Francesco Tumino, Sergio Tosoni, Paolo D’Agosta, Valeria Russo, Carlo Enrico Bottani, Andrea Li Bassi, Carlo Spartaco Casari
The Raman spectrum of monolayer (ML) MoS$ _2$ is remarkably affected by the interaction with metals. In this work we studied ML-MoS$ _2$ supported by the Ag(111) and Ag(110) surfaces by using a combined experimental and theoretical approach. The MoS$ _2$ layer was directly grown on atomically clean Ag(111) and Ag(110) surfaces by pulsed laser deposition, followed by in-situ thermal annealing under ultra-high vacuum conditions. The morphology and structure of the two systems were characterized in-situ by scanning tunneling microscopy, providing atomic-scale information on the relation between the MoS$ _2$ lattice and the underlying surface. Raman spectroscopy revealed differences between the two MoS$ _2$ -metal interfaces, especially concerning the behavior of the out-of-plane $ A’_1$ vibrational mode, which splits into two contributions on Ag(110). The metal-induced effects on MoS$ _2$ vibrational modes are further evidenced by transferring MoS$ _2$ onto a more inert substrate (SiO$ _2$ /Si), where the MoS$ _2$ Raman response displays a more ``freestanding-like’’ behavior. The experimental data were interpreted with the support of ab-initio calculations of the vibrational modes, which provided insight into the effect of interface properties, such as strain and out-of-plane distortion. Our results highlight the influence of the interaction with metals on MoS$ _2$ vibrational properties, and show the high sensitivity of MoS$ _2$ Raman modes to the surface structure of the supporting metal.
Materials Science (cond-mat.mtrl-sci)
This document is the unedited Author’s version of a Submitted Work that was subsequently accepted for publication in The Journal of Physical Chemistry C, copyright \c{opyright} 2025 American Chemical Society after peer review. To access the final edited and published work see this https URL
J. Phys. Chem. C 2025, 129, 2, 1457-1466
SEMIDV: A Compact Semiconductor Device Simulator with Quantum Effects
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-04-02 20:00 EDT
In this paper, I present SEMIDV - a compact semiconductor device simulator incorporating quantum effects. SEMIDV solves the Poisson-Drift-Diffusion equations for semiconductor devices and provides a user-friendly Python interface for scripting and data analysis. Localization landscape theory is introduced to provide quantum corrections to the Drift-Diffusion equation. This theory directly solves the ground state of the Schrodinger equation without further approximation, offering an efficient solution for quantum effect modeling. Additionally, a compact mobility model considering ballistic transport is developed to capture the ballistic length dependence of mobility and the velocity overshoot effect in short-channel devices. Finally, a study on a nanosheet FET using SEMIDV is conducted. I analyze the electrical characteristics of a state-of-the-art GAA/RibbonFET with a 6 nm gate length and discuss the effects of velocity overshoot and quantum confinement on currents and capacitances. A design for an ultra-short-channel transistor with a gate length down to 4.5 nm with a Vdd = 0.45 V is proposed to push the boundaries of integrated circuit technology further.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Applied Physics (physics.app-ph)
Submitted to IEEE TED
Interface-Generated Spin Current Induced Magnetoresistance in RuO2/Py Heterostructures
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-04-02 20:00 EDT
Akashdeep Akashdeep, Ewiese Mohammad Ababneh, Christin Schmitt, Edgar Galíndez-Ruales, Felix Fuhrmann, Timo Kuschel, Mathias Kläui, Vivek Pravin Amin, Gerhard Jakob
Altermagnets, a recently discovered class of magnetic materials exhibiting ferromagnetic-like spin-split bands and antiferromagnetic-like compensated magnetic order, have attracted significant interest for next-generation spintronic applications. Ruthenium dioxide (RuO2) has emerged as a promising altermagnetic candidate due to its compensated antiparallel magnetic order and strong spin-split electronic bands. However, recent experimental and theoretical reports also suggest that RuO2 may be non-magnetic in its ground state, underscoring the need for deeper investigations into its magnetic character. Specifically, the (100)-oriented RuO2 films are expected to generate spin currents with transverse spin polarization parallel to the Néel vector. Here, we investigate magnetotransport in epitaxial RuO2/Permalloy (Py) heterostructures to examine spin Hall magnetoresistance and interfacial effects generated in such systems. Our measurements reveal a pronounced negative angular-dependent magnetoresistance for variation of magnetic field direction perpendicular to the charge current direction. Detailed temperature-, magnetic field-, and crystallographic orientation-dependent measurements indicate that interface-generated spin current (IGSC) at the RuO2/Py interface predominantly governs the observed magnetoresistance. This shows that strong interface effects dominate over possible altermagnetic contributions from RuO2. Our results show that the role of interface-generated spin currents is crucial and should not be overlooked in studies of altermagnetic systems. A critical step in this direction is disentangling interfacial from altermagnetic contributions. The insight into interfacial contributions from altermagnetic influences is essential for the advancement of RuO2 based spintronic memory and sensing applications.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Modifications in the photoionization cross-section of a quantum dot with position-dependent effective mass
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-04-02 20:00 EDT
Carlos Magno O. Pereira, Denise Assafrão, Frankbelson dos S. Azevedo, A. G. de Lima, Cleverson Filgueiras, Edilberto O. Silva
In this work, we investigate the photoionization cross-section of an electron confined in a quantum dot, considering the position-dependent variation of the effective mass through the parameter $ \gamma$ . We used a theoretical model based on the Schrödinger equation, in which $ \gamma$ influences the energy levels and wave functions through an effective potential obtained from the harmonic oscillator potential - which, in the limit $ \gamma = 0$ , reduces to the original harmonic oscillator potential. Furthermore, we compared the modifications in the photoionization cross-section of these quantum systems with the constant-mass case. Our results demonstrate that even a small variation in $ \gamma$ significantly impacts the photoionization process’s amplitude and peak position. We also found that for specific values of $ \gamma$ , an inversion occurs: The amplitude, which initially increases as the quantum dot absorbs the photon, begins to decrease. Additionally, we observed that the optical transitions involving the ground state restrict the admissible values of $ \gamma$ to negative values only. These results may have relevant implications for designing optoelectronic devices based on quantum dots with adjustable mass properties.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
15 pages, 13 figures
Phase Transformation Kinetics Model for Metals
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-04-02 20:00 EDT
Daniel N. Blaschke, Abigail Hunter, Dean L. Preston
We develop a new model for phase transformation kinetics in metals by generalizing the Levitas-Preston (LP) phase field model of martensite phase transformations (see Levitas and Preston (2002a,b); Levitas, Preston and Lee (2003)) to arbitrary pressure. Furthermore, we account for and track: the interface speed of the pressure driven phase transformation, properties of critical nuclei, as well as nucleation at grain sites and on dislocations and homogeneous nucleation. The volume fraction evolution of each phase is described by employing KJMA (Kolmogorov, 1937; Johnson and Mehl, 1939; Avrami, 1939, 1940, 1941) kinetic theory. We then test our new model for iron under ramp loading conditions and compare our predictions for the $ \alpha\to\epsilon$ iron phase transition to experimental data of Smith et al. (2013). More than one combination of material and model parameters (such as dislocation density and interface speed) led to good agreement of our simulations to the experimental data, thus highlighting the importance of having accurate characterization data regarding the microstructure of the sample in question.
Materials Science (cond-mat.mtrl-sci)
31 pages, 7 figures
A Clue on Small-Capacitance Josephson Junction: What to Expect from Cooper Pair Ideal Conductor and Ohmic Resistor in Parallel?
New Submission | Superconductivity (cond-mat.supr-con) | 2025-04-02 20:00 EDT
Francesco Giuseppe Capone, Antonio de Candia, Vittorio Cataudella, Naoto Nagaosa, Carmine Antonio Perroni, Giulio De Filippis
By using analytical and Worldline Monte Carlo approaches, we investigate the effects induced by quantum phase fluctuations combined with quasiparticle subgap and shunt resistances on a small-capacitance Josephson junction. By using the linear response theory in the presence of two biasing schemes, we prove that the ideal conduction, foreseen in the pioneering papers on this topic, is not robust against either quantum phase fluctuations or dissipative effects. By including both of them in the Hamiltonian, we prove that an increase of the Ohmic dissipation strength induces a Berezinskii-Kosterlitz-Thouless quantum phase transition in thermodynamic equilibrium. Then we study charge and phase fluctuations at the thermodynamic equilibrium within the linear response theory. We find that the phase particle motion, in a quantum Josephson junction, does not change from diffusive to localized, resulting in an insulator-superconductor transition, as is commonly believed. At the transition, we prove that: i) the motion of the phase particle changes from ballistic to localized; ii) by turning on the coupling with the environment, a long-lived excitation at finite frequency emerges in the charge response function: it evolves first into a resonance and then disappears at the transition. Consequences beyond the linear response regime are investigated, leading to an alternative comprehensive physical picture for this system: we predict a transition from a dissipative quasiparticle current to a polaronic Cooper pair current.
Superconductivity (cond-mat.supr-con), Statistical Mechanics (cond-mat.stat-mech), Quantum Physics (quant-ph)
11 pages, 7 figures
Universal KPZ Fluctuations for Moderate Deviations of Random Walks in Random Environments
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-04-02 20:00 EDT
Jacob Hass, Hindy Drillick, Ivan Corwin, Eric Corwin
The theory of diffusion seeks to describe the motion of particles in a chaotic environment. Classical theory models individual particles as independent random walkers, effectively forgetting that particles evolve together in the same environment. Random Walks in a Random Environment (RWRE) models treat the environment as a random space-time field that biases the motion of particles based on where they are in the environment. We provide a universality result for the moderate deviations of the transition probability of this model over a wide class of choices of random environments. In particular, we show the convergence of moments to those of the multiplicative noise stochastic heat equation (SHE), whose logarithm is the Kardar-Parisi-Zhang (KPZ) equation. The environment only filters into the scaling limit through one parameter, which depends explicitly on the statistical description of the environment. This forms the basis for our introduction, in arXiv:2406.17733, of the extreme diffusion coefficient.
Statistical Mechanics (cond-mat.stat-mech), Mathematical Physics (math-ph), Probability (math.PR)
Interfaces in epitaxially grown Zn3P2 nanowires and their composition dependent optoelectronic properties for photovoltaic applications
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-04-02 20:00 EDT
Simon Escobar Steinvall, Francesco Salutari, Jonas Johansson, Ishika Das, Sebastian Lehmann, Stephen A. Church, M. Chiara Spadaro, Patrick Parkinson, Jordi Arbiol, Kimberly A. Dick
Epitaxially grown nanowires have shown promise for photovoltaic applications due to their nanophotonic properties. Moreover, the mechanical properties of nanowires can reduce crystallographic defect formation at interfaces to help enable new material combinations for photovoltaics. One material that stands to benefit from the nanowire morphology is zinc phosphide (Zn3P2), which despite promising optoelectronic properties has experienced limited applicability due to challenges achieving heteroepitaxy, stemming from its large lattice parameter and coefficient of thermal expansion. Herein, we identify the requirements for successful epitaxy of Zn3P2 nanowires using metalorganic chemical vapour deposition and the impact on interface structure and defect formation. Furthermore, using high-throughput optical spectroscopy we were able to demonstrate shifts in the photoluminescence intensity and energy by tuning the V/II ratio during growth, highlighting the compositional tunability of the optoelectronic properties of Zn3P2 nanowires.
Materials Science (cond-mat.mtrl-sci)
Space-Charge Limited Schottky Diodes with Wide-Bandgap Thin-film Oxide Heterojunctions
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-04-02 20:00 EDT
Non-crystalline thin-film Schottky diodes are cost-effective but often exhibit unreliable electrical characteristics due to material imperfections. In this work, I present a Schottky diode structure utilizing in-situ grown Ta2O5 and ZnO thin films deposited at room temperature. The low conduction band offset across the interface of the heterogeneous oxides facilitates efficient electron injection under forward bias. Capacitance-voltage characterization reveals a robust Schottky barrier at the Au/Ta2O5 interface without a significant barrier thinning effect, enabling high-voltage breakdown up to 65V and a high on/off ratio of 1X$ 10^8$ . In demonstrations, the thin-film structure shows Schottky contact characteristics using even a relatively low work function metal of ITO, allowing the operation of transparent Schottky diodes. The diodes show additional potential for applications, including RF-to-DC conversion leveraging space charge capacitance at the Ta2O5/ZnO junction and rectifying resistive random access memory devices. This work highlights a promising approach for integrating low-cost, high-reliability Schottky diodes into back-end-of-line processes for wireless electronics and power devices.
Materials Science (cond-mat.mtrl-sci)
One-Dimensional Potassium Chains on Silicon Nanoribbons
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-04-02 20:00 EDT
Tongtong Chen, Wenjia Zhang, Xiaobei Wan, Xiaohan Zhang, Yashi Yin, Jinghao Qin, Fengxian Ma, Juntao Song, Ying Liu, Wen-Xiao Wang
Silicon nanoribbons (SiNRs), characterized by a pentagonal structure composed of silicon atoms, host one-dimensional (1D) Dirac Fermions and serve as a minimalist atomic template for adsorbing various heteroatoms. Alkali-metal (AM) atoms, such as Na and K, with electronic structures comparable to those of hydrogen are of particular interest for such adsorption studies. However, the adsorption of AM atoms on SiNRs and its tunation on the properties of SiNRs have not yet been fully explored. In this study, we examined the adsorption of K atoms on high-aspect-ratio SiNRs and the resultant electronic properties using a combination of scanning tunneling microscopy (STM) and density functional theory calculations. K atoms prefer to adsorb on double- and multi-stranded SiNRs owing to the low adsorption energies at these sites. Each K atom and its three nearest Si atoms exhibit a triangular morphology resulting from charge transfer between K and Si atoms, as verified by theoretical calculations. As the K coverage of the SiNRs increased, the K atoms organize into 1D zigzag chains on the SiNRs. Moreover, K adsorption on the SiNRs was determined to be reversible. The deposition of K atoms on the SiNRs was achieved using a voltage pulse of the STM tip, without damaging the SiNRs structure. In addition, K adsorption effectively modulates the Dirac cone position of the SiNRs relative to the Fermi level. This study unveils the adsorption mechanism of AM atoms on SiNRs, providing a useful approach for heteroatom adsorption on other nanoribbons.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Silicon Nanoribbons, Potassium, STM, STS
Chemical and Morphological Transformations of a Ag-Cu Nanocatalyst During CO2 Reduction Reaction
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-04-02 20:00 EDT
Gustavo Zottis Girotto, Maximilian Jaugstetter, Dongwoo Kim, Ruan M. Martins, André R. Muniz, Miquel Salmeron, Slavomir Nemsak, Fabiano Bernardi
The conversion of CO2 into high-value chemicals through a photoreduction reaction in water is a promising route to reduce the dependence on fossil fuels. Ag nanoparticles can drive this reaction via localized surface plasmon resonance, but their low selectivity limits usage in industry. Enhancing selectivity toward hydrocarbons or alcohols requires addition of a co-catalyst such as Cu. However, the stabilized surface state created by Ag-Cu interactions is still poorly understood. In this work, soft x-ray Ambient-Pressure X-ray Photoelectron Spectroscopy (AP-XPS) and Grazing-Incidence X-ray Scattering (AP-GIXS) were used to investigate the evolution of Ag-Cu nanoparticles under CO2RR-like conditions. AP-XPS revealed Ag and Cu surface and sub-surface diffusion, while AP-GIXS tracked change of shape and size of nanoparticles induced by diffusion mechanics. Under 532 nm laser irradiation, further oxidation of Cu and Ag sub-surface diffusion were observed, providing invaluable insights into the dynamic restructuring of the catalyst under reaction conditions.
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Turbulent diffusion and dispersion in a superfluid
New Submission | Quantum Gases (cond-mat.quant-gas) | 2025-04-02 20:00 EDT
Yuan Tang, Sosuke Inui, Yiming Xing, Yinghe Qi, Wei Guo
Single-body diffusion and two-body dispersion are fundamental processes in classical turbulence, governing particle mixing and transport. However, their behaviors in superfluid turbulence remain largely unexplored. In this study, we numerically investigate the diffusion and relative dispersion of quantized vortices and superfluid parcels in the 0 K limit in two distinct turbulence regimes: ultra-quantum turbulence, characterized by a randomized vortex tangle, and quasiclassical turbulence, in which locally polarized vortices create large-scale flows resembling classical turbulence. Our results reveal that while vortex segments exhibit similar superdiffusion behavior at short times in both regimes, superfluid parcels behave differently: following the same superdiffusion scaling in ultra-quantum turbulence but deviating significantly in quasiclassical turbulence. This contrast provides a key clue to the origin of short-time superdiffusion, a puzzle since its recent discovery. Additionally, we show that two-body dispersion of both vortex segments and superfluid parcels exhibits distinct scaling behaviors in ultra-quantum and quasiclassical turbulence, highlighting fundamental differences in these two turbulence regimes. Our findings bridge a critical gap in superfluid turbulence research, offering new insights into turbulent transport in inviscid quantum fluids.
Quantum Gases (cond-mat.quant-gas), Other Condensed Matter (cond-mat.other)
6 pages, 4 figures
Chemical Pressure Tuning of Multipolar and Magnetic Orders in Ba$2$(Cd${1-x}$Ca$_x$)ReO$_6$ Double Perovskites
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-04-02 20:00 EDT
Koki Shibuya, Daigorou Hirai, Koshi Takenaka
Double perovskite compounds containing 5d transition metal elements have been extensively studied as platforms for multipolar order phenomena stemming from spin-orbit-entangled 5d electrons. In this study, we examine the interplay between crystal structure, multipolar order, and magnetic order in solid solutions of double perovskites with the 5d1 electronic configuration: Ba2CdReO6 and Ba2CaReO6, which exhibit distinct electronic orders. The substitution of larger Ca2+ ions for Cd2+ in Ba2CdReO6, systematically increases the lattice constant with increasing the amount of substitution x. Although the spin-orbit-entangled J = 3/2 state remains intact upon substitution, both the quadrupolar order below Tq = 25 K and the canted antiferro-magnetic (AFM) order below Tm = 12 K in Ba2CdReO6 are progressively suppressed as x increases. Magnetization measurements reveal that the canted AFM order is suppressed at x = 0.6, transitioning to a colinear AFM order, while the quadrupolar order persists up to x = 0.9. The experimental electronic phase diagram, summarizing the dependence of electronic orders on lattice constants, aligns well with the theoretical phase diagram considering electric quadrupolar interactions [G. Chen et al., Phys. Rev. B 82, 174440 (2010)]. This correspondence confirms that chemical pressure induced by substitution effectively tunes the interaction between 5d electrons. The results highlight the potential of chemical pressure to modulate multipolar interactions, paving the way for novel multipolar properties in 5d electron systems.
Strongly Correlated Electrons (cond-mat.str-el), Materials Science (cond-mat.mtrl-sci)
7 pages, 4 figures
Phys. Rev. Mater. 9, 034406 (2025)
Stability analysis of Bose Gas: effect of external trapping and three-body interaction with Gross-Pitaevskii equation in Tonks-Girardeau regimes
New Submission | Quantum Gases (cond-mat.quant-gas) | 2025-04-02 20:00 EDT
R. Sasireka, O.T. Lekeufack, A. Uthayakumar, S. Sabari
In this work, we investigate the stability aspects of quintic Gross-Pitaevskii (GP) equation with the presence and absence of external trapping potential for a Bose Gas (BG) in both the Tonks-Girardeau (TG) and the super Tonks-Girardeau (sTG) regimes. For this purpose, we compute both analytically and numerically a pure quintic GP equation with the presence of the scattering lengths. Using the time-dependent variational approach, we derive the equations of motion and effective potential of the system for both cases. Through the effective potential, we discuss the stability properties of pure quintic GP equation and obtain the modulational instability condition of BECs. The variational results are verified by means of direct numerical simulations using split-step Crank-Nicolson method and the observed results are in agreement with the analytical predictions.
Quantum Gases (cond-mat.quant-gas)
17 pages, 10 figures
Fast reversal of Néel vectors in antiferromagnets via domain-wall motion driven by vertically injected spin currents
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-04-02 20:00 EDT
Jiaxin Du, Mei Li, Bin Xi, Xue Zhang, Yi Sun, Chun-Gui Duan, Jie Lu
In this work, we investigate the steady propagation of 180-degree domain walls (180DWs) of Néel vectors in thin antiferromagnetic strips under perpendicularly injected spin currents with various polarization orientations. Our results show that only spin currents polarized normally to the strip plane guarantee a quick and steady rigid flow of 180DWs, thus realize a fast reversal of Néel vectors in antiferromagnets (AFMs). Different from the common current-in-plane'' geometry which is feasible only for metallic AFMs, our current-out-of-plane’’ layout under investigation can further apply to insulating AFMs (which are more common in real applications) via quantum tunneling effect. Results from this work paves the way for fine control of Néel vectors in (both metallic and insulating) AFM strips and further development of novel magnetic nanodevices based on them.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
6 pages, 3 figures
Polarization-dependent photocurrent in a quadrilateral-shaped bulk crystalline tellurium chip with near-infrared light excitation
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-04-02 20:00 EDT
Hiro Munekata, Gakuto Kusuno, Kohei Miyazaki, Takuya Satoh
A circular polarization-dependent photocurrent is exclusively observed along the direction parallel to the helical axis in millimeter-sized quadrilateral-shaped bulk crystalline tellurium samples. The deterioration of the polarization-dependent character of unclear origin is also recorded. The estimate of the gyrotropic photoconductivity constant Betha in the context of the circular photogalvanic effect yields the value of approximately 5 micro-A/W based on experimental results obtained under a relatively weak excitation of 1.7 W/cm2. A comparison of this Betha value with those reported in previous studies is also discussed. Enhancement of Betha value may be achievable with bulk samples of superior crystalline quality.
Materials Science (cond-mat.mtrl-sci)
31 pages, 8 figures, 1 table. 47 references; submitted to one of academic journals for review
A Method to Suppress Polar Kerr Signal in a Longitudinal Magneto-Optic-Kerr-Effect Measurement
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-04-02 20:00 EDT
Ryan W. Greening, Elyssa D. DeVisscher, Xin Fan (Department of Physics and Astronomy, University of Denver)
The Magneto-Optical-Kerr-Effect (MOKE) is a convenient technique to study the magnetization of thin films. However, both polar and longitudinal MOKE responses contribute to the total Kerr response in a typical longitudinal MOKE measurement. Here, we present a simple optical technique to suppress the polar MOKE response in the oblique angle incidence by exploiting differences between polar and longitudinal MOKE responses upon double reflection from the sample. By using a mirror to reflect the beam and by selectively using a quarter waveplate, the polar or longitudinal MOKE signals can be suppressed, and therefore studied separately using the same oblique experimental setup. To demonstrate the feasibility of this technique, we use an out-of-plane magnetized Pt/Co/Pt film as well as a Pt/Co/Cu/NiFe Heterostructure with both in-plane and out-of-plane magnetization. We show that the polar MOKE of the CoPt film can be suppressed by a factor of 6 compared to a conventional MOKE measurement. By accounting for birefringence, we further reduce the polar MOKE response in a longitudinal MOKE measurement of the Pt/Co/Cu/NiFe film by over 160 times compared to a conventional oblique-angle MOKE measurement.
Materials Science (cond-mat.mtrl-sci)
Engineering living worms and active crystals with colloidal “feedback-pullers”
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-04-02 20:00 EDT
Using computer simulations, we study the dynamics of colloidal particles with time-delayed feedback interactions. In particular, here we consider “feedback-pullers”, i.e.~colloidal particles that are pulled away from their current position towards an attractive ring centred around their past position. For a single particle, small rings lead to reduced diffusive motion while large rings render activity to the particle. For multiple particles, the particles not only feel their own attractive ring but are also attracted by the rings around all other particles. As expected, for ring sizes larger than the particle diameter, the feedback leads to crystallites whose lattice constant is set by the feedback ring radius. However, here we demonstrate that for long delays (compared to the Brownian time) the colloidal particles start to oscillate around their lattice positions, with the crystallites ultimately collapsing to a close-packed lattice whose lattice constant corresponds to the particle diameter. This effect is caused by the time delay between the particle misplacement within the lattice and the corresponding change in the feedback force. Further, we show that apart from the expected hexagonal crystallites, the time delay may result in the formation of uncommon new states in the case that the ring size is chosen slightly smaller than the particle diameter. Here, particles self-assemble into and move collaboratively as “living worms” or as active square-lattice crystallites.
Soft Condensed Matter (cond-mat.soft)
10 pages, 5 figures
A dual-scale stochastic analysis framework for creep failure considering microstructural randomness
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-04-02 20:00 EDT
Weichen Kong, Yanwei Dai, Xiang Zhang, Yinghua Liu
Creep failure under high temperatures is a complex multiscale and multi-mechanism issue involving inherent microstructural randomness. To investigate the effect of microstructures on the uniaxial/multiaxial creep failure, a dual-scale stochastic analysis framework is established to introduce the grain boundary (GB) characteristics into the macroscopic analysis. The nickel-base superalloy Inconel 617 is considered in this study. Firstly, the damage mechanisms of GBs are investigated based on the crystal plasticity finite element (CPFE) method and cohesive zone model (CZM). Subsequently, based on the obtained GB damage evolution, a novel Monte Carlo (MC) approach is proposed to establish the relationship between the GB orientation and area distribution and macroscopic creep damage. Finally, a dual-scale stochastic multiaxial creep damage model is established to incorporate the influence of the random GB orientation and area distribution. With the numerical application of the proposed creep damage model, the random initiation and growth of creep cracks in the uniaxial tensile specimen and the pressurized tube are captured and analyzed. The proposed stochastic framework effectively considers the inherent randomness introduced by GB characteristics and efficiently realizes full-field multiscale calculations. It also shows its potential applications in safety evaluation and life prediction of creep components and structures under high temperatures.
Materials Science (cond-mat.mtrl-sci), Classical Physics (physics.class-ph)
Unifying Interpretations of Phase Transitions in the Vicsek Model: Correlation Length as a Diagnostic Tool
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-04-02 20:00 EDT
Wenhao Yu, Zinuo Li, Liufang Xu
Vicsek Model is widely used in simulations of dry active matter. We re-examined two typical phase transitions in the original Vicsek model by using the velocity correlation length. One is the noise-driven disordered-to-ordered phase transition driven by noise, which was initially considered as a second-order transition (continuous transition), but was later demonstrated by Chate’s detailed study to be a first-order transition. The other one is the disordered-to-ordered phase transition driven by average distance between particles, which is a second-order transition and satisfies the hyper-scaling relation of continuous transitions. We have discovered the change of correlation length during transition indicates a critical point in continuous transition while not in the discontinuous situation. We have also provided a method to classify phase transitions in active matter systems by using the correlation length and summarized previous work within the same framework. Finally, we end up with a potential application in experiments of bactirial swarms and robotic swarms. We hope our work paves the way for both theory and experiment development of active matter.
Soft Condensed Matter (cond-mat.soft), Biological Physics (physics.bio-ph)
7 pages,6 figures
Cascading symmetry constraint during machine learning-enabled structural search for sulfur induced Cu(111)-$(\sqrt{43}\times\sqrt{43})$ surface reconstruction
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-04-02 20:00 EDT
Florian Brix, Mads-Peter Verner Christiansen, Bjørk Hammer
In this work, we investigate how exploiting symmetry when creating and modifying structural models may speed up global atomistic structure optimization. We propose a search strategy in which models start from high symmetry configurations and then gradually evolve into lower symmetry models. The algorithm is named cascading symmetry search and is shown to be highly efficient for a number of known surface reconstructions. We use our method for the sulfur induced Cu (111) $ (\sqrt{43}\times\sqrt{43})$ surface reconstruction for which we identify a new highly stable structure which conforms with experimental evidence.
Materials Science (cond-mat.mtrl-sci)
J. Chem. Phys. 160, 174107 (2024)
Signatures of exceptional points in multiterminal superconductor-normal metal junctions
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-04-02 20:00 EDT
Oliver Solow, Karsten Flensberg
We study a non-Hermitian, multiterminal superconducting-normal system in order to identify experimental signatures of exceptional points. We focus on a minimal setting with a single spinful level, spin-dependent normal leads, and a noncollinear magnetic field. This system hosts both topologically-protected, as well as symmetry-protected exceptional points. Using an exact transport formalism, we show that the exceptional points are visible through spectroscopy of the Andreev states, but that they have a minor effect on the Josephson current. We also argue that these findings hold with interactions.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
5+3 pages, 5 figures
Exploring the role of four-phonon scattering in the lattice thermal transport of LaMoN$_3$
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-04-02 20:00 EDT
Manjari Jain, Sanchi Monga, Saswata Bhattacharya
In this work, we systematically investigate the lattice thermal conductivity ($ \kappa_L$ ) of LaMoN$ _3$ in the $ C$ 2/$ c$ and $ R$ 3$ c$ phases using first-principles calculations combined with the Boltzmann transport equation. In the $ C$ 2/$ c$ phase, $ \kappa_L$ exhibits strong anisotropy, with values of 0.75 W/mK, 1.89 W/mK, and 0.82 W/mK along the a, b, and c axes, respectively, at 300 K. In contrast, the $ R$ 3$ c$ phase shows nearly isotropic thermal conductivity, with values of 6.28 W/mK, 7.05 W/mK, and 7.31 W/mK along the a, b, and c directions. In both phases, acoustic phonons dominate thermal transport. However, in the $ C$ 2/$ c$ phase, the absence of an acoustic-optical gap results in increased three-phonon scattering leading to smaller values of $ \kappa_L$ . Additionally, four-phonon scattering plays a dominant role in the C2/c phase, reducing $ \kappa_L$ by approximately 96%, whereas in the $ R3c$ phase, it leads to a smaller but still significant reduction of ~50%. These results highlight the critical role of four-phonon interactions in determining the thermal transport properties of LaMoN$ _3$ and reveal the stark contrast in thermal conductivity between its two structural phases.
Materials Science (cond-mat.mtrl-sci)
Light-driven modulation of proximity-enhanced functionalities in hybrid nano-scale systems
New Submission | Other Condensed Matter (cond-mat.other) | 2025-04-02 20:00 EDT
Mattia Benini, Umut Parlak, Sophie Bork, Jaka Strohsack, Richard Leven, David Gutnikov, Fabian Mertens, Evgeny Zhukov, Rajib Kumar Rakshit, Ilaria Bergenti, Andrea Droghetti, Tomaz Mertelj, Valentin Alek Dediu, Mirko Cinchetti
Advancing quantum information and communication technology (qICT) requires smaller and faster components with actively controllable functionalities. This work presents a novel strategy for dynamically modulating magnetic properties via proximity effects controlled by light. We demonstrate this concept using hybrid nanoscale systems composed of C60 molecules proximitized to a cobalt metallic ferromagnetic surface, where proximity interactions are particularly strong. Our findings show that by inducing excitons in the C60 molecules with resonant ultrashort light pulses, we can significantly modify the interaction at the cobalt/C60 interface, leading to a striking 60% transient shift in the frequency of the dipolar ferromagnetic resonance mode of the Cobalt. This effect, detected via a specifically designed time-resolved magneto-optical Kerr effect (tr-MOKE) experiment, persists on a timescale of hundreds of picoseconds. Since this frequency shift directly correlates with a transient change in the anisotropy field (an essential parameter for technological applications) our findings establish a new paradigm for ultrafast optical control of magnetism at the nanoscale.
Other Condensed Matter (cond-mat.other), Materials Science (cond-mat.mtrl-sci)
Pressure-Induced Volume Collapse and Metallization in Inverse Spinel Co$_2$TiO$_4$
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-04-02 20:00 EDT
Mrinmay Sahu, Souvick Chakraborty, Bidisha Mukherjee, Bishnupada Ghosh, Asish Kumar Mishra, Satyabrata Raj, Goutam Dev Mukherjee
The structural, vibrational, electronic, and magnetic properties of inverse spinel $ Co_2TiO_4$ (CTO-Sp) under high pressure (HP) conditions are systematically investigated using X-ray diffraction, Raman spectroscopy, in situ optical microscopy, and first-principles density functional theory (DFT) calculations. At ambient conditions, CTO-Sp exhibits a cubic phase with a space group $ Fd\bar{3}m$ and it undergoes two notable structural phase transitions at HP. The first transition, occurring at approximately 7.2 GPa, leads to the tetragonal-$ I4_1/amd$ phase with minimal alteration in unit cell volume. Subsequently, a second transition to an orthorhombic phase with a mixed space group $ Fddd$ and $ Cmcm$ is observed around 17.3 GPa. This second structural transition corresponds to a first-order phase transition involving a significant reduction in unit cell volume of approximately 17.5$ %$ . The bulk compressibility of CTO-Sp and its HP post-spinel phases is almost equal to the average polyhedral compressibility within each phase. The absence of Raman modes beyond 23 GPa is compelling evidence for metallization. DFT calculations reveal a high-spin to low-spin transition, accompanied by the collapse of local magnetic moments in the Cmcm orthorhombic phase, leading to the sample’s pressure-induced metallization.
Materials Science (cond-mat.mtrl-sci)
Driving collective current excitations using light: The time-dependent $GW$ approach
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-04-02 20:00 EDT
Chin Shen Ong, Denis Golež, Angel Rubio, Olle Eriksson, Hugo U. R. Strand
Electron-electron interactions in solids give rise to longitudinal collective charge excitations known as plasmons, which are observable corresponding to resonances in the density-density response function of the electrons. In this study, we demonstrate that current-current interactions can induce a novel type of collective excitation for systems of noninteracting and interacting electrons under nonequilibrium conditions, which we term as “curron”. By taking into account the interaction between the vector potential generated by electronic currents and the vector potential driving them, we construct a system of interacting currents mediated by vector potentials. We show that this leads to the emergence of a quasiparticle associated with transverse collective current excitations, corresponding to resonances in the current-current response function. We account for electron-electron interaction by solving the Kadanoff-Baym equations within the non-equilibrium two-time GW approach using sodium metal as our prototypical metal.
Materials Science (cond-mat.mtrl-sci)
Dipolar-exchange spin waves in thin bilayers
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-04-02 20:00 EDT
Rob den Teuling, Ritesh Das, Artem V. Bondarenko, Elena V. Tartakovskaya, Gerrit E. W. Bauer, Yaroslav M. Blanter
We investigate the dipolar-exchange spin wave spectrum in thin ferromagnetic bilayers with inplane magnetization, incorporating interlayer exchange coupling and intra- and interlayer dipolar interactions. In the continuum approximation we analyze the nonreciprocity of propagating magnetic stray fields emitted by spin waves as a function of the relative orientation of the layer magnetizations that are observable by magnetometry of synthetic antiferromagnets or weakly coupled type-A van der Waals antiferromagnetic bilayers as a function of an applied magnetic field.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
7 pages, 3 figures
Complex magnetic exchange, anisotropy and skyrmionic textures in two-dimensional FeXZ$_{2}$ (\textit{X} = Nb, Ta and \textit{Z} = S, Se, Te) ferromagnets
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-04-02 20:00 EDT
Soheil Ershadrad, Nikola Machacova, Arnob Mukherjee, Vladislav Borisov, Olle Eriksson, Biplab Sanyal
FeNbTe$ _{2}$ , long known as a van der Waals metallic system, has recently been resynthesized and shown to exhibit ferromagnetic order. In this study, using first-principles density functional theory (DFT), we aim to provide a deeper insight into the magnetic properties of FeNbTe$ _{2}$ and its related compounds (FeXZ$ _{2}$ , \textit{X} = Nb, Ta; \textit{Z} = S, Se, Te), in their two-dimensional form, including their non-centrosymmetric Janus counterparts. Our results indicate that these materials are energetically, dynamically, thermally, and mechanically stable, supporting the possibility of FeNbTe$ _{2}$ exfoliation and potential for experimental realization of new compounds. An evolutionary structure search suggests that FeNbTe$ _{2}$ retains its monoclinic symmetry in the monolayer form. Our analysis of hopping parameters obtained from Wannierization of DFT bands shows that the nearest-neighbor magnetic interactions are primarily direct, while second-nearest and more distant interactions are mediated by the chalcogen atoms. Interestingly, although the second-nearest-neighbor interactions are smaller in magnitude, they appear to play a key role in determining the magnetic ordering in these systems. We also find evidence of canted magnetic anisotropy in FeXZ$ _{2}$ compounds, with relatively strong magnetocrystalline anisotropy energy and easy-axis deviations of up to 41$ ^\circ$ from the out-of-plane direction-an uncommon and potentially useful feature for spintronic applications. Curie temperatures estimated from Monte Carlo simulations are below room temperature but above cryogenic levels for most compounds. Micromagnetic simulations revealed that Janus-structured FeNbSeTe can host Néel-type skyrmions even in the absence of an external magnetic field, making this compound a suitable candidate for further experimental studies.
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Other Condensed Matter (cond-mat.other), Quantum Physics (quant-ph)
15 pages, 4 figures
Single-gap two-band superconductivity well above the Pauli limit in non-centrosymmetric TaIr$_2$B$_2$
New Submission | Superconductivity (cond-mat.supr-con) | 2025-04-02 20:00 EDT
J. Kacmarcik, Z. Pribulova, T. Shiroka, F. Kosuth, P.Szabo, M. J. Winiarski, S. Krolak, J. Jaroszynski, T. Shang, R. J. Cava, C. Marcenat, T. Klein, T. Klimczuk, P. Samuely
Non-centrosymmetric superconducting materials represent an exciting class of novel superconductors featuring a variety of unconventional properties, including mixed-parity pairing and very high upper critical fields. Here, we present a comprehensive study of TaIr$ _2$ B$ _2$ (with $ T_c$ = 5.1 K), using a set of complementary experimental methods, including bulk- and surface-sensitive techniques. We provide evidence that this system is a two-band, yet it behaves as a single-gap superconductor with a strong coupling. The upper critical field of TaIr$ _2$ B$ _2$ significantly exceeds the Pauli limit and exhibits a nearly linear temperature dependence down to the lowest temperatures. This behavior, rarely seen in superconductors, is discussed in terms of anti-symmetric spin-orbit interaction, two-band-, and strong-coupling effects, as well as disorder.
Superconductivity (cond-mat.supr-con)
10 pages, 8 figures, suppl. material
Bridging-induced Aggregation in Neutral Polymers: Dynamics and Morphologies
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-04-02 20:00 EDT
Hitesh Garg, Satyavani Vemparala
Using molecular dynamics simulations, we investigate the aggregation behavior of neutral stiff (rod-like) and flexible polymer chains mediated by attractive crowders. Attractive crowders serve as bridging agents, inducing aggregation through effective intra-polymer attractions. The critical monomer-crowder attraction strength ($ \epsilon_{mc}^\ast$ ) required for aggregation differs notably between rigid rods and flexible polymers. Interestingly, this aggregation threshold closely matches the critical attraction required for the extended-to-collapsed (coil-globule) transition of a single flexible polymer chain, suggesting a fundamental connection between single-chain collapse and multi-chain aggregation. Furthermore, we demonstrate that $ \epsilon_{mc}^\ast$ decreases with increasing system density and larger crowder sizes, highlighting the synergistic roles of crowding effects and crowder dimensions. Aggregate morphologies exhibit strong dependence on polymer flexibility: rigid rods predominantly form elongated cylindrical bundles, whereas flexible polymers aggregate into compact spherical clusters. These findings provide comprehensive insights into how bridging interactions driven by attractive crowders regulate polymer aggregation dynamics and morphologies, emphasizing the importance of polymer rigidity, crowder size, and system density.
Soft Condensed Matter (cond-mat.soft), Biological Physics (physics.bio-ph), Chemical Physics (physics.chem-ph), Computational Physics (physics.comp-ph)
7 main figures and 11 pages
Frustrated Bose ladder with extended range density-density interaction
New Submission | Quantum Gases (cond-mat.quant-gas) | 2025-04-02 20:00 EDT
Sourav Biswas, E. Rico, Tobias Grass
When hard-core bosons on a two-leg ladder get frustrated by ring exchange interactions, the elusive d-wave Bose liquid (DBL) can be stabilized, a bosonic analog of a correlated metal. Here, we analyze the effect of extended Hubbard interactions on the DBL phase. Strikingly, these interactions are found to act in favor of the exotic Bose liquid. This observation is of immediate relevance for physical systems in which non-local exchange processes occur as a consequence of extended-range density-density interactions. Our observation also helps to achieve DBL physics in a synthetic-dimension ladder, where on-site interactions translate into non-local interactions along a synthetic rung. In this context, we also consider the extreme limit, in which the local hardcore constraint is elevated to an effective rung blockade. In addition to the enhancement of DBL physics due to extended-range density-density interactions, we also find signatures of an interesting intermediate phase between the superfluid and the DBL regime. This phase, labeled as the density modulated s-wave paired (DMSP) phase, combines features of density wave and s-wave pairing. Our results offer new insights into the physics of frustrated bosons by highlighting the influence of density-density interaction and rung-blockade.
Quantum Gases (cond-mat.quant-gas), Strongly Correlated Electrons (cond-mat.str-el), Quantum Physics (quant-ph)
9 pages, 9 figures
Multiple topological corner states in the continuum of extended kagome lattice
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-04-02 20:00 EDT
Shun-Peng Zhang, Ming-Jian Gao, Wei Jia, Jun-Hong An
The kagome lattice is renowned for its exotic electronic properties, such as flat bands, Dirac points, and Van Hove singularities. These features have provided a fertile ground for exploring exotic quantum phenomena. Here, we discover that a breathing kagome lattice with long-range hoppings can host multiple zero-energy corner states, which emerge as topologically protected bound states in the continuum (BICs). This result demonstrates that additional hopping control can induce further non-trivial physics of the kagome lattice. Since the zero-energy corner states in the continuum are intertwined with a substantial number of zero-energy bulk states, we also develop a momentum-space topological characterization theory to precisely quantify the number of corner states, revealing a general bulk-corner correspondence. Furthermore, we uncover three distinct types of topological phase transitions (TPTs) for the BICs driven by shifts in the spatial localization of zero-energy bulk and/or edge states. These TPTs are exactly captured by our characterization theory. This work provides deep insights into the topological physics of the kagome lattice and broadens the understanding of its electronic properties
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
7+6 pages,4+1 figures
Accelerated Inorganic Materials Design with Generative AI Agents
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-04-02 20:00 EDT
Izumi Takahara, Teruyasu Mizoguchi, Bang Liu
Designing inorganic crystalline materials with tailored properties is critical to technological innovation, yet current generative computational methods often struggle to efficiently explore desired targets with sufficient interpretability. Here, we present MatAgent, a generative approach for inorganic materials discovery that harnesses the powerful reasoning capabilities of large language models (LLMs). By combining a diffusion-based generative model for crystal structure estimation with a predictive model for property evaluation, MatAgent uses iterative, feedback-driven guidance to steer material exploration precisely toward user-defined targets. Integrated with external cognitive tools-including short-term memory, long-term memory, the periodic table, and a comprehensive materials knowledge base-MatAgent emulates human expert reasoning to vastly expand the accessible compositional space. Our results demonstrate that MatAgent robustly directs exploration toward desired properties while consistently achieving high compositional validity, uniqueness, and material novelty. This framework thus provides a highly interpretable, practical, and versatile AI-driven solution to accelerate the discovery and design of next-generation inorganic materials.
Materials Science (cond-mat.mtrl-sci)
Interaction Quench Dynamics and Stability of Quantum Vortices in Rotating Bose-Einstein Condensates
New Submission | Quantum Gases (cond-mat.quant-gas) | 2025-04-02 20:00 EDT
L. A. Machado, B. Chatterjee, M. A. Caracanhas, L. Madeira, V. S. Bagnato, B. Chakrabarti
We theoretically investigate the non-equilibrium dynamics of quantum vortices in a two-dimensional rotating Bose-Einstein condensate following an interaction quench. Using an ab initio and numerically exact quantum many-body approach, we systematically tune the interplay between interaction strength and angular velocity to prepare quantum vortices in various configurations and examine their post-quench dynamics. Our study reveals distinct dynamical regimes: First, vortex distortion accompanied by density cloud fragmentation, matching the initial vortex number and second, vortex revival, where fragmented densities interact and merge. Notably, we observe complete vortex revival dynamics in the single-vortex case, pseudo-revival in double and triple vortex configurations, and chaotic many-body dynamics in systems with multiple vortices. Our results reveal a universal out-of-equilibrium response of quantum vortices to interaction quenches, highlighting the importance of many-body effects with a possible exploration in quantum simulation with ultracold quantum fluids.
Quantum Gases (cond-mat.quant-gas)
Database of Tensorial Optical and Transport Properties of Materials From the Wannier Function Method
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-04-02 20:00 EDT
Zhenyao Fang, Ting-Wei Hsu, Qimin Yan
The discovery and design of functional materials for energy harvesting and electronic applications require accurate predictions of their optical and transport properties. While several existing databases contain the first-order optical properties and the electron transport properties calculated from high-throughput first-principles calculations, the amount of material entries is often limited and those functional properties are often reported in scalar form. Comprehensive databases for the tensorial properties still remain inadequate, which prevents from capturing the anisotropic effect in materials and the development of advanced machine learning models that incorporate the space group symmetry of materials. Therefore, in this work we present the largest-to-date database of tensorial optical properties (optical conductivity, shift current) and the database of tensorial transport properties (electrical conductivity, thermal conductivity, Seebeck coefficient, thermoelectric figure of merit zT) for 7301 materials, calculated from the Wannier function method. The quality of the Wannier functions were validated by the maximal spread of the Wannier functions and by the comparison with the band structures from first-principles calculations, ensuring the accuracy of the calculated properties. These results contribute to the systematic study the functional properties for diverse materials and can benefit future data-driven discovery of candidate materials for optoelectronic and thermoelectric applications.
Materials Science (cond-mat.mtrl-sci)
Synthesis of Cobalt Grown from Co-S Eutectic in High Magnetic Fields
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-04-02 20:00 EDT
Steven Flynn, Caeli L. Benyacko, Matúš Mihalik, Jared Lee, Fuyan Ma, Michael E. Bates, Shubham Sinha, Khalil A. Abboud, Marian Mihalik, Mark W. Meisel, James J. Hamlin
Samples of Co were grown directly in the ferromagnetic state under equilibrium conditions using a cobalt sulfide flux. Magnetic fields up to 9 T were applied during growth, and isolated Co products exhibit progressively elongated morphologies, from cubes to rectangular rods to needle-like tendrils with poorly-defined facets. The degree of elongation of the major axis was found to correlate with magnetic field direction, strength, and gradient. Two-dimensional X-ray diffraction data indicate some level of polycrystalline-like samples, and quantitative analyses (Le Bail and Rietveld) of the one-dimensional data confirm the presence of hcp and fcc phases. The magnetic responses indicate a partial alignment of the magnetic easy-axis of the hcp phase along the magnetic field present during growth.
Materials Science (cond-mat.mtrl-sci)
8 pages, 6 figures
$\mathbb{Z}_2$ topological invariants from the Green’s function diagonal zeros
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-04-02 20:00 EDT
Florian Simon, Corentin Morice
We investigate the relationship between the analytical properties of the Green’s function and $ \mathbb{Z}_2$ topological insulators, focusing on three-dimensional inversion-symmetric systems. We show that the diagonal zeros of the Green’s function in the orbital basis provide a direct and visual way to calculate the strong and weak $ \mathbb{Z}_2$ topological invariants. We introduce the surface of crossings of diagonal zeros in the Brillouin zone, and show that it separates TRIMs of opposite parity in two-band models, enabling the visual computation of the $ \mathbb{Z}_2$ invariants by counting the relevant TRIMs on either side. In three-band systems, a similar property holds in every case except when a trivial band is added in the band gap of a non-trivial two-band system, reminiscent of the band topology of fragile topological insulators. Our work could open avenues to experimental measurements of $ \mathbb{Z}_2$ topological invariants using ARPES measurements.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Shear Stress Build-up Under Constant Strain Conditions in Soft Glassy Materials
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-04-02 20:00 EDT
Vivek Kumar, Gareth H McKinley, Yogesh M Joshi
In this work, we investigate the transient rheological behavior of two soft glassy materials: a clay dispersion and a silica gel, emphasizing their unconventional shear stress build-up behavior under conditions of constant imposed strain. For both materials, the elastic modulus and static yield stress undergo time-dependent evolution or aging. In addition, following an intense period of pre-shearing (i.e. shear-melting or destructuration), the material relaxation time is observed to show a stronger than linear dependence on the sample age, suggestive of hyper-aging dynamics. We show that these features are consistent with non-monotonic steady-state shear stress/shear rate flow curves characterized by a local stress minimum. When a steady shear flow is suddenly ceased, and the total imposed sample strain is held constant, both materials show an initial relaxation of the shear stress followed by a period of shear stress buildup, resulting in a local minimum in the evolution of shear stress with time. For the clay dispersion, the intensity of these effects increases with higher pre-shear rates, whereas for the silica gel, the effects are largely independent of the pre-shear rate. We also propose a simple time-dependent linear Maxwell model, which qualitatively predicts the experimentally observed trends in which the shear stress build-up is directly related to a monotonic increase in the elastic modulus, giving keen insight into this peculiar phenomenon.
Soft Condensed Matter (cond-mat.soft), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
40 pages, 18 figures
Passive objects in a chiral active bath: from micro to macro
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-04-02 20:00 EDT
Cory Hargus, Federico Ghimenti, Julien Tailleur, Frédéric van Wijland
We present a detailed derivation of the Langevin dynamics obeyed by a massive rigid body immersed in a chiral active bath. We show how the antisymmetric nature of the noise leads to an unusual relationship between the Langevin equation describing stochastic trajectories and the Fokker-Planck equation governing the time-evolution of the probability density. The chirality of the bath endows the object dynamics with odd diffusivity, odd mobility, and rotational ratchet effects that depend on the object symmetries. For rotationally-symmetric objects, we show that a hidden time-reversal symmetry leads to separate effective equilibrium descriptions for the translational and rotational degrees of freedom. Finally, starting from the bath dynamics, we construct a multipole expansion to quadrupolar order that allows predicting the far-field current and density modulation induced by the object on the bath.
Statistical Mechanics (cond-mat.stat-mech), Soft Condensed Matter (cond-mat.soft)
Nonperturbative treatment of a quenched Langevin field theory
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-04-02 20:00 EDT
Friederike Ihssen, Valerio Pagni, Jamir Marino, Sebastian Diehl, Nicolò Defenu
We present a novel approach within the functional renormalization group framework for computing critical exponents that characterize the time evolution of out-of-equilibrium many-body systems. Our approach permits access to quantities involved in the renormalization procedure, using an expansion about time-translation invariant problems. This expansion can be upgraded to a fully time-dependent computation by iteration. As a prototypical example, we compute the aging exponent $ \theta$ describing the dynamics of model A following a sudden quench to the critical point. Already at leading order, the approach demonstrates remarkable accuracy when compared with MC simulations and resummed perturbative expansions in the range $ 2<d<4$ . This yields results that surpass those of the two-loop $ \epsilon$ expansion in accuracy and match analytically known benchmarks at large $ N$ . These findings contribute to a deeper understanding of out-of-equilibrium universality and open new avenues for non-perturbative studies of critical dynamics, as well as for exploring the critical behavior of systems with spatial boundaries.
Statistical Mechanics (cond-mat.stat-mech)
14 pages, 3 figures
Percolation of systems having hyperuniformity or giant number-fluctuations
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-04-02 20:00 EDT
Sayantan Mitra, Indranil Mukherjee, P. K. Mohanty
We generate point configurations (PCs) by thresholding the local energy of the Ashkin-Teller model in two dimensions (2D) and study the percolation transition at different values of $ \lambda$ along the critical Baxter line by varying the threshold that controls the particle density $ \rho$ . For all values of $ \lambda$ , the PCs exhibit power-law correlations with a decay exponent $ a$ that remains independent of $ \rho$ and varies continuously with $ \lambda$ . For $ \lambda < 0$ , where the PCs are hyperuniform, the percolation critical behavior is identical to that of ordinary percolation. In contrast, for $ \lambda > 0$ , the configurations exhibit giant number fluctuations, and all critical exponents vary continuously, but form a superuniversality class of percolation transition in 2D.
Statistical Mechanics (cond-mat.stat-mech)
7 pages, 6 Figures, Supplemental Material (2 page)
Exact Diagonalization, Matrix Product States and Conformal Perturbation Theory Study of a 3D Ising Fuzzy Sphere Model
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-04-02 20:00 EDT
Andreas M. Läuchli, Loïc Herviou, Patrick H. Wilhelm, Slava Rychkov
Numerical studies of phase transitions in statistical and quantum lattice models provide crucial insights into the corresponding Conformal Field Theories (CFTs). In higher dimensions, comparing finite-volume numerical results to infinite-volume CFT data is facilitated by choosing the sphere $ S^{d-1}$ as the spatial manifold. Recently, the fuzzy sphere regulator in Ref. [Zhu et al, Phys. Rev. X 13 021009 (2023)] has enabled such studies with exact rotational invariance, yielding impressive agreement with known 3D Ising CFT predictions, as well as new results. However, systematic improvements and a deeper understanding of finite-size corrections remain essential. In this work, we revisit the fuzzy sphere regulator, focusing on the original Ising model, with two main goals. First, we assess the robustness of this approach using Conformal Perturbation Theory (CPT), to which we provide a detailed guidebook. We demonstrate how CPT provides a unified framework for determining the critical point, the speed of light, and residual deviations from CFT predictions. Applying this framework, we study finite-size corrections and clarify the role of tuning the model in minimizing these effects. Second, we develop a novel method for extracting Operator Product Expansion (OPE) coefficients from fuzzy sphere data. This method leverages the sensitivity of energy levels to detuning from criticality, providing new insights into level mixing and avoided crossings in finite systems. Our work also includes validation of CPT in a 1+1D Ising model away from the integrable limit.
Statistical Mechanics (cond-mat.stat-mech), Strongly Correlated Electrons (cond-mat.str-el), High Energy Physics - Lattice (hep-lat), High Energy Physics - Theory (hep-th)
51 pages, 12 figures, comments welcome
Universality of the topological phase transition in the interacting Haldane model
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-04-02 20:00 EDT
Simone Fabbri, Alessandro Giuliani, Robin Reuvers
The Haldane model is a standard tight-binding model describing electrons hopping on a hexagonal lattice subject to a transverse, dipolar magnetic field. We consider its interacting version for values of the interaction strength that are small compared to the bandwidth. We study the critical case at the transition between the trivial and the `topological’ insulating phases, and we rigorously establish that the transverse conductivity on the dressed critical line is quantized at a half-integer multiple of $ e^2/h$ : this is the average of the integer values of the Hall conductivity in the insulating phases on either side of the dressed critical line. Together with previous results, this fully characterizes the nature of the phase transition between different Hall plateaus and proves its universality with respect to many-body interactions. The proof is based on a combination of constructive renormalization group methods and exact lattice Ward identities.
Strongly Correlated Electrons (cond-mat.str-el), Mathematical Physics (math-ph)
17 pages, 3 figures
Optimizing Metal-Organic Chemical Vapor Deposition for Ultrawide Band-Gap MgSiN2 Thin Films
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-04-02 20:00 EDT
Chenxi Hu, Abdul Mukit, Vijay Gopal Thirupakuzi Vangipuram, Christopher Chae, Jinwoo Hwang, Kathleen Kash, Hongping Zhao
Orthorhombic II-IV nitride semiconductors offer an expanded and more tunable material set with unique properties, while maintaining close compatibility with the wurtzite crystal structure of the III-nitrides. In particular, MgSiN2, a II-IV nitride closely lattice matched to GaN and AlN has a band gap suitable for photonic applications in the UV-C wavelength region. MgSiN2 is also a promising candidate to exhibit ferroelectricity, which has only been observed in very few nitride materials. This study builds on our previous work on the metal-organic chemical vapor deposition (MOCVD) of MgSiN2 thin films grown on GaN-on-sapphire and c-plane sapphire substrates by exploring higher growth temperature windows, resulting in higher crystalline quality and improved interfaces. Correlations between the growth conditions (Mg:Si precursor molar flow rate ratio, reactor pressure, and growth temperatures from 900C to 960C) and the resultant film quality are investigated for films grown on GaN-on-sapphire. High-resolution transmission electron microscopy (HR-TEM) reveals high-quality orthorhombic single-crystal MgSiN2, confirming successful epitaxial growth on GaN. Optical transmittance measurements indicate the direct band gap is 6.34-6.36 eV and indirect band gap is 5.77-5.81 eV, affirming the realization of an ultrawide-band gap II-IV nitride semiconductor that is structurally compatible with existing III-nitride device platforms.
Materials Science (cond-mat.mtrl-sci), Applied Physics (physics.app-ph)
28 pages, 3 tables, 10 figures
Constitutive relations from images
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-04-02 20:00 EDT
Adeline Wihardja, Kaushik Bhattacharya
Constitutive relations close the balance laws of continuum mechanics and serves as the surrogate for a material in the design and engineering process. The problem of obtaining the constitutive relations is an indirect inverse problem where both the relation and the quantities that define the relation have to be inferred from experimental observations. The advent of full-field observation techniques promises a new ability of learning constitutive relations in realistic operational conditions. However, this is done in two steps, first obtaining deformations from the images, and then obtaining the constitutive relation from deformations and forces. This leads to a variety of difficulties. In this paper, we propose a novel approach that enables us to obtain constitutive relation directly from the raw data consisting of images and force measurements.
Materials Science (cond-mat.mtrl-sci)
Field free Josephson diode effect in Ising Superconductor/Altermagnet Josephson junction
New Submission | Superconductivity (cond-mat.supr-con) | 2025-04-02 20:00 EDT
Arindam Boruah, Saumen Acharjee, Prasanta Kumar Saikia
Altermagnets (AMs) are an exotic class of antiferromagnet that exhibit spin-splitting even at the absence of net global magnetization and spin-orbit coupling (SOC) effects. In this work, we investigated theoretically, the supercurrent nonreciprocity in an Ising Superconductor/Altermagnet/Ising Superconductor (ISC/AM/ISC) Josephson junction which revealed asymmetric Josephson critical currents, $ 0 - \pi$ transitions and anomalous current-phase relationship (CPR). A strong Josephson diode efficiency (JDE) is observed due to the combined effects of AM strength and orientations in a conventional SC even in absence of SOC. However, it significantly enhances in presence of intrinsic SOC (ISOC), resulting in pronounced diode effect in both single and double band ISC/AM based Josephson junction. Additionally, it is observed that JDE is more prominent at higher AM strengths with intermediate orientations in all scenario. Notably, it is significantly suppressed for orientations $ 0^\circ$ and $ 45^\circ$ . Our results also indicate that barrier transparency and AM lengths play a crucial role in optimizing the JDE. In a single-band ISC/AM system JDE persists for any AM length, while reduces at longer AM junction in case of a double-band ISC/AM system. Moreover, our results suggest that a diode efficiency of $ \sim 52%$ can be achieved in the proposed Josephson junction in both single and double band ISC/AM Josephson junction by considering strong AM strength. Furthermore, single band ISC offers wide AM orientation range in contrast to double band ISC for better tunability and optimization of JDE. Our findings highlight the impact of AM strength, orientation and ISOC on the JDE efficiency offering insights for superconducting diode design.
Superconductivity (cond-mat.supr-con)
Efficient spin filtering through Fe$_4$GeTe$_2$-based van der Waals heterostructures
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-04-02 20:00 EDT
Masoumeh Davoudiniya, Biplab Sanyal
Utilizing ab initio simulations, we study the spin-dependent electronic transport characteristics within Fe$ _4$ GeTe$ _2$ -based van der Waals heterostructures. The electronic density of states for both free-standing and device-configured Fe$ _4$ GeTe$ _2$ (F4GT) confirms its ferromagnetic metallic nature and reveals a weak interface interaction between F4GT and PtTe$ _2$ electrodes, enabling efficient spin filtering. We observe a decrease in the magnetic anisotropy energy of F4GT in the device configuration, indicating reduced stability of magnetic moments and heightened sensitivity to external conditions. The transmission eigenstates of PtTe$ _2$ / monolayer F4GT/PtTe$ _2$ heterostructures demonstrate interference patterns affected by relative phases and localization, notably different in the spin-up and spin-down channels. The ballistic transport through a double-layer F4GT with a ferromagnetic configuration sandwiched between two PtTe$ _2$ electrodes is predicted to exhibit an impressive spin polarization of 97$ %$ with spin-up electrons exhibiting higher transmission probability than spin-down electrons. Moreover, we investigate the spin transport properties of Fe$ _4$ GeTe$ _2$ /GaTe/Fe$ _4$ GeTe$ _2$ van der Waals heterostructures sandwiched between PtTe$ _2$ electrodes to explore their potential as magnetic tunnel junctions (MTJs) in spintronic devices. The inclusion of GaTe as a 2D semiconducting spacer between F4GT layers results in a tunnel magnetoresistance (TMR) of 487$ %$ at low bias and decreases with increasing bias voltage. In general, our findings underscore the potential of F4GT / GaTe / F4GT heterostructures to advance spintronic devices based on van der Waals materials.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci), Computational Physics (physics.comp-ph)
13 pages, 11 figures
Nanoscale Adv. 6, 6278 (2024)
Bimodality of local structural ordering in extremely confined hard disks
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-04-02 20:00 EDT
A. Trokhymchuk, T. Bryk, A. Huerta
By combining computer simulations and a unit cell model approach, we study the apparent bimodality of local structural ordering in a system of confined hard disks. It is shown that a two-dimensional (2D) array of hard disks confined laterally within a quasi-1D hard wall channel of the width commensurate with the bulk 2D triangular lattice at disk close packing, possesses a bimodal probability distribution for the distance between disks’ left and right nearest neighbors. The observed feature aligns with the concept of locally favored structures intensively exploited in the studies of anomalous thermodynamic and kinetic behavior of hydrogen-bonding fluids, except that the reported case is driven by entropic bonding only. The bimodality is observed in a range of densities associated with the vicinity of freezing transition in bulk 2D hard disks, indicating a crossover from the “gas-like” to “liquid-like” state in confined quasi-1D hard disks. Such a phenomenon was not reported for bulk 2D hard disks and is physically unexpected for confined q1D hard disks.
Soft Condensed Matter (cond-mat.soft)
Electron beam precession for a serial crystallography experiment in a TEM
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-04-02 20:00 EDT
Sergi Plana-Ruiz, Penghan Lu, Govind Ummethala, Rafal Dunin-Borkowski
During the last few years, serial electron crystallography (Serial Electron Diffraction, SerialED) has been gaining attention for the structure determination of crystalline compounds that are sensitive to the irradiation of the electron beam. By recording a single electron diffraction pattern per crystal, indexing hundreds or even thousands of measured particles, and merging the reflection intensities of the successfully indexed patterns, one can retrieve crystal structure models with strongly mitigated beam damage contributions. However, one of the technique’s bottlenecks is the need to collect that many diffraction patterns, which, done in an automated way, results in low indexing rates. This work demonstrates how to overcome this limitation by performing the serial crystallography experiment following a semi-automated routine with a precessed electron beam (Serial Precession Electron Diffraction, SerialPED). The precession movement increases the number of reflections present in the diffraction patterns and dynamical effects related to specific orientations of the crystals with respect to the electron beam are smoothed out. This leads to more uniform reflection intensities across the serial dataset and a smaller number of patterns are required to merge the reflection intensities for good statistics. Furthermore, structure refinements based on the dynamical diffraction theory become accessible, providing a novel approach for more accurate structure models. In this context, the use of beam precession is presented as an advantageous tool for serial electron crystallography as it enables reliable crystal structure analysis with a lower amount of diffraction data.
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Many-body \textit{ab initio} study of quasiparticle & optical excitations and exciton analysis in LiZnAs and ScAgC for photovoltaic applications
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-04-02 20:00 EDT
Vinod Kumar Solet, Sudhir K. Pandey
Using first-principles density-functional theory and many-body excited-state calculations, we study the quasiparticle band structure, optical and excitonic properties of two half-Heusler (HH) compounds, namely LiZnAs and ScAgC, for photovoltaic (PV) applications. Our results reveal a direct bandgap semiconducting behavior in LiZnAs (ScAgC) with a value of 1.5 (1.0) eV under an accurate G$ _0$ W$ _0$ calculation. The highest value of the imaginary part of dielectric function is found as 52 (87), 77 (87), 88 (91) using the independent-quasiparticle approximation, local field effects in random-phase approximation, and electron-hole interaction in the Bethe-Salpeter equation, respectively. Both materials demonstrate a high refractive index, high absorption coefficients (1.2-1.6 $ \times 10^6 cm^{-1}$ ), and low reflectivity (< 40%) in active region of the solar spectrum. The triply degenerate bright excitons (exciton A) at the main absorption peak and a considerable number of bright excitonic states in the visible region, are observed; however, the excitons oscillator strength are comparatively weaker in ScAgC than in LiZnAs. We further discuss the exciton character contributing to intense optical interband transitions and reveal that direct band gap is associated to the loosely bound exciton A state with binding energy of 45 (56) meV in LiZnAs (ScAgC). Exciton A is found to be highly localized (delocalized) in momentum (real) space, indicating the presence of Mott-Wannier type excitons at bandgap. Finally, we assess the solar efficiencies using the spectroscopic limited maximum efficiency (SLME) model and find SLME values of 32% for LiZnAs and 31% for ScAgC at a 0.4 $ \mu$ m thin-film thickness. These findings highlight the significant role of excitons in solar energy absorption process and also suggest that both are highly suitable candidates for single-junction thin-film solar cells.
Materials Science (cond-mat.mtrl-sci)
15 pages, 9 figures
Real-space methods for ab initio modelling of surfaces and interfaces under external potential bias
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-04-02 20:00 EDT
Kartick Ramakrishnan, Gopalakrishnan Sai Gautam, Phani Motamarri
Accurate ab initio modelling of surfaces and interfaces, especially under an applied external potential bias, is important for describing and characterizing various phenomena that occur in electronic, catalytic, and energy storage devices. Leveraging the ability of real-space density functional theory (DFT) codes to accommodate generic boundary conditions, we introduce two methods for applying an external potential bias that can be suitable for modelling surfaces and interfaces. In the first method, an external constant electric field is applied by modifying the DFT Hamiltonian via the introduction of an auxiliary linear potential while solving the electrostatic potential arising in DFT using a Poisson equation with zero-Neumann boundary conditions. The second method directly enforces the desired external potential bias by imposing constraints on the electrostatic potential, thereby naturally mimicking experimental conditions. We describe the underlying DFT governing equations for the two setups within the real-space formalism employing finite-element discretization. First, we validate the constant electric field setup within real-space finite-element DFT (DFT-FE) with an equivalent approach using plane-wave DFT (i.e., using periodic boundary conditions) on three representative benchmark systems, namely La-terminated Li$ _7$ La$ _3$ Zr$ _2$ O$ _{12}$ , GaAs (111), and Al FCC (111) slabs. Subsequently, we present a comprehensive evaluation of the two setups in terms of the average ground-state properties, such as surface and adsorption energies. The methods developed in our work provide an attractive alternative to plane-wave DFT approaches in applying external potential bias that usually suffer from the periodic boundary conditions restrictions and poor scalability on parallel computing architectures.
Materials Science (cond-mat.mtrl-sci)
37 pages, 8 figures, 2 tables
From point patterns to networks: to what extent does the Delaunay triangulation reproduce key spatial and density information?
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-04-02 20:00 EDT
Eli Newby, Wenlong Shi, Yang Jiao, Salvatore Torquato, Réka Albert
It is important that a spatial network’s construction algorithm reproduces the structural properties of the original physical embedding. Here, we assess the Delaunay triangulation as a spatial network construction algorithm for seven different types of 2D point patterns, including hyperuniform systems. The latter are characterized by completely suppressed normalized infinite-wavelength density fluctuations. We demonstrate that the quartile coefficients of dispersion of multiple centrality measures are capable of rank-ordering hyperuniform and nonhyperuniform systems independently, but they cannot distinguish a system that is nearly hyperuniform from hyperuniform systems. Thus, we investigate the local densities of the point pattern and of the network. We reveal that there is a strong correlation between local densities in the point pattern and network in nonhyperuniform systems, but there is no such correlation in hyperuniform systems. When calculating the pair-correlation function and local density covariance function on the point pattern and network, the point pattern and network functions are similar only in nonhyperuniform systems. In hyperuniform systems, the triangulation has a positive covariance of local network densities in pairs of nodes that are close together that is not present in the point patterns. Thus, we demonstrate that the Delaunay triangulation accurately captures the density fluctuations of the point pattern only when the point pattern possesses a positive local density covariance at small distances. Such positive correlation is seen in most real-world systems, so the Delaunay triangulation is generally an effective tool for building a spatial network from a 2D point pattern, but there are situations (i.e., disordered hyperuniform systems) where we caution that the Delaunay triangulation would not be effective at capturing the underlying physical embedding.
Statistical Mechanics (cond-mat.stat-mech)
19 Pages, 8 Figures, 2 Tables