Showing 1–50 of 927 results for author: Wang, Q

Bridging Microscopic Constructions and Continuum Topological Field Theory of Three-Dimensional Non-Abelian Topological Order

Authors: Yizhou Huang, Zhi-Feng Zhang, Qing-Rui Wang, Peng Ye

Abstract: Here we provide a microscopic lattice construction of excitations, fusion, and shrinking in a non-Abelian topological order by studying the three-dimensional quantum double model. We explicitly construct lattice operators that create, fuse, and shrink particle and loop excitations, systematically derive their fusion and shrinking rules, and demonstrate that non-Abelian shrinking channels can be co… ▽ More Here we provide a microscopic lattice construction of excitations, fusion, and shrinking in a non-Abelian topological order by studying the three-dimensional quantum double model. We explicitly construct lattice operators that create, fuse, and shrink particle and loop excitations, systematically derive their fusion and shrinking rules, and demonstrate that non-Abelian shrinking channels can be controllably selected through internal degrees of freedom of loop operators. Most importantly, we show that the lattice shrinking rules obey the fusion--shrinking consistency relations predicted by twisted $BF$ field theory, providing solid evidence for the validity of field-theoretical principles developed over the past years. In particular, we compute the full set of excitations, fusion, and shrinking data at the microscopic lattice level and verify exact agreement between the microscopic $\mathbb{D}_4$ quantum double lattice model and the continuum $BF$ field theory with an $AAB$ twist and $(\mathbb{Z}_2)^3$ gauge group, thereby placing the latter field theory, originally discovered in 2018 in connection with Borromean-ring braiding, on a solid microscopic footing. Our results bridge continuum topological field theory and exactly solvable lattice models, elevate fusion--shrinking consistency from a continuum field-theoretical principle to a genuine topological phenomenon defined at the microscopic lattice scale, and provide a concrete microscopic foundation for experimentally engineering higher-dimensional non-Abelian topological orders in controllable quantum simulators, such as trapped-ion systems. △ Less

Submitted 24 December, 2025; originally announced December 2025.

Comments: Length limit. The complete version of Abstract is shown in PDF

A voltage-responsive strongly dipolar-coupled macrospin network with emergent dynamics for computing

Authors: Xinglong Ye, Zhibo Zhao, Qian Wang, Jiangnan Li, Fernando Maccari, Ning Lu, Christian Dietz, Esmaeil Adabifiroozjaei, Leopoldo Molina-Luna, Yufeng Tian, Lihui Bai, Guodong Wang, Konstantin Skokov, Yanxue Chen, Shishen Yan, Robert Kruk, Horst Hahn, Oliver Gutfleisch

Abstract: Emergent behavior,which arises from local interactions between simple elements,is pervasive in nature. It underlies the exceptional energy-efficient computing in our brains. However,realizing such dynamics in artificial materials, particularly under low-energy stimuli, remains a fundamental challenge.Here we harness and amplify them to construct a strongly dipolar-coupled network of SmCo5 macrospi… ▽ More Emergent behavior,which arises from local interactions between simple elements,is pervasive in nature. It underlies the exceptional energy-efficient computing in our brains. However,realizing such dynamics in artificial materials, particularly under low-energy stimuli, remains a fundamental challenge.Here we harness and amplify them to construct a strongly dipolar-coupled network of SmCo5 macrospins at wafer scale, which can exhibit intrinsic interaction-driven collective dynamics in response to voltage pulses. The network combines three essential ingredients,i.e.strong dipolar coupling enabled by large single-domain macrospin, giant voltage control of coercivity over nearly 1000-fold, the largest reported to date, and a disordered network topology with frustrated Ising-like energy landscape. When stimulated by 1 V pulses, the network enters a regime where interaction-driven magnetic behaviors emerge, including spontaneous demagnetization, greatly enhanced magnetization modulation, reversible freeze and resume evolution and stochastic convergence toward low-energy magnetic configurations. All these behaviors are completely absent at the single-nanomagnet level. Furthermore, by constructing micromagnetic models of the strongly dipolar-coupled macrospin networks calibrated to experiments, we show that the resulting nonlinear, high-dimensional collective dynamics, which are characteristic of strongly-interacting systems, can enable accurate chaotic Mackey-Glass prediction and multiclass drone-signal classification. Our work establishes the voltage-responsive strongly-coupled SmCo5 network as a mesoscopic platform for probing emergent magnetic dynamics previously inaccessible under ambient conditions.It also suggests a fundamental distinct route towards scalable,low-voltage computing, one rooted in native physical interaction-driven collective dynamics at the network level. △ Less

Submitted 23 December, 2025; originally announced December 2025.

Topological surface phonons modulate thermal transport in semiconductor thin films

Authors: Zhe Su, Shuoran Song, Qi Wang, Jian-Hua Jiang

Abstract: While phonon topology in crystalline solids has been extensively studied, its influence on thermal transport-especially in nanostructures-remains elusive. Here, by combining first-principles-based machine learning potentials with the phonon Boltzmann transport equation and molecular dynamics simulations, we systematically investigate the role of topological surface phonons in the in-plane thermal… ▽ More While phonon topology in crystalline solids has been extensively studied, its influence on thermal transport-especially in nanostructures-remains elusive. Here, by combining first-principles-based machine learning potentials with the phonon Boltzmann transport equation and molecular dynamics simulations, we systematically investigate the role of topological surface phonons in the in-plane thermal transport of semiconductor thin films (Si, 4H -SiC, and c-BN). These topological surface phonons, originating from nontrivial acoustic phonon nodal lines, not only serve as key scattering channels for dominant acoustic phonons but also contribute substantially to the overall thermal conductivity. Remarkably, for these thin semiconductor films below 10 nm this contribution can be as large as over 30% of the in-plane thermal conductivity at 300 K, and the largest absolute contribution can reach 82 W/m-K, highlighting their significant role in nanoscale thermal transport in semiconductors. Furthermore, we demonstrate that both temperature and biaxial strain provide effective means to modulate this contribution. Our work establishes a direct link between topological surface phonons and nanoscale thermal transport, offering the first quantitative assessment of their role and paving the way for topology-enabled thermal management in semiconductors. △ Less

Submitted 21 December, 2025; originally announced December 2025.

Unusual strain relaxation and Dirac semimetallic behavior in epitaxial antiperovskite nitrides

Authors: Ting Cui, Zihan Xu, Qinghua Zhang, Xiaodong Zhang, Qianying Wang, Dongke Rong, Songhee Choi, Axin Xie, Hongyun Ji, Can Wang, Chen Ge, Hongjian Feng, Shanmin Wang, Kuijuan Jin, Liang Si, Er-Jia Guo

Abstract: Antiperovskite nitrides (X3AN) are the structural analogues to perovskite oxides, while their epitaxial growth and electronic properties remain largely unexplored. We report the successful synthesis of Ni3InN thin films on substrates with different lattice constants. First-principles phonon calculations confirm the dynamical stability of cubic phase Ni3InN, providing the basis for epitaxial synthe… ▽ More Antiperovskite nitrides (X3AN) are the structural analogues to perovskite oxides, while their epitaxial growth and electronic properties remain largely unexplored. We report the successful synthesis of Ni3InN thin films on substrates with different lattice constants. First-principles phonon calculations confirm the dynamical stability of cubic phase Ni3InN, providing the basis for epitaxial synthesis. High-resolution scanning transmission electron microscopy reveals coherent (001)-oriented interfaces when Ni3InN is grown on LaAlO3 and SrTiO3, while an unexpected (011)-orientation forms on DyScO3, aligning with surface-energy predictions. Transport measurements highlight a strain-controlled Fermi-liquid behavior, correlated with variations in the Ni-3d bandwidth and hybridization. Band structure calculations reveal a dual character near the Fermi level: a high-mobility Dirac-like band and a Ni-3d manifold that drives strange-metal transport with a reduced slope compared to oxide perovskites. The formal Ni valence (+2/3) places Ni3InN in an overdoped correlated-metal regime, distinguishing from most perovskite oxides. This positions antiperovskite nitrides as a promising platform for investigating overdoped Fermi liquids and strange-metal behavior. △ Less

Submitted 19 December, 2025; originally announced December 2025.

Comments: 4 figures, 33 pages

Observation of square-like moire lattice and quasicrystalline order in twisted rock-salt nitrides

Authors: Dongke Rong, Qinghua Zhang, Ting Cui, Qianying Wang, Hongyun Ji, Axin Xie, Songhee Choi, Qiao Jin, Chen Ge, Can Wang, Shanmin Wang, Kuijuan Jin, Er-Jia Guo

Abstract: Twistronics, which exploits moire modulation of lattice and electronic structures in twisted bilayers, has emerged as a powerful approach to engineer novel quantum states. Recent efforts have expanded beyond two dimensional van der Waals (vdWs) crystals to more complex, strongly correlated materials, where interfacial moire effects can dominate physical properties. Here we demonstrate a generaliza… ▽ More Twistronics, which exploits moire modulation of lattice and electronic structures in twisted bilayers, has emerged as a powerful approach to engineer novel quantum states. Recent efforts have expanded beyond two dimensional van der Waals (vdWs) crystals to more complex, strongly correlated materials, where interfacial moire effects can dominate physical properties. Here we demonstrate a generalizable route to fabricate twisted bilayers of transition metal nitrides with vdWs like interfaces, using freestanding CrN membranes as a model system. Twisted bilayer CrN (tCrN) is realized by employing cubic alkaline earth metal monoxides as sacrificial layers, enabling the assembly of clean, controllable interfaces. Electron ptychography reveals well defined, periodic square moire superlattices in tCrN. For a twist angle of 16.3 degree, we identify a nearly commensurate moire lattice with coincident Cr columns, whereas at 45 degree we uncover localized octagonal quasicrystalline order with clear self-similarity. These results establish a practical platform for twisted TMNs and open avenues to explore moire-induced atomic configurations and emergent correlated phenomena in nitride based heterostructures. △ Less

Submitted 19 December, 2025; originally announced December 2025.

Comments: 5 figures, 20 pages

Probing ground-state degeneracies of a strongly interacting Fermi-Hubbard model with superconducting correlations

Authors: Sebastiaan L. D. ten Haaf, Sebastian Miles, Qingzhen Wang, A. Mert Bozkurt, Ivan Kulesh, Yining Zhang, Christian G. Prosko, Michael Wimmer, Srijit Goswami

Abstract: The Fermi-Hubbard model and its rich phase diagram naturally emerges as a description for a wide range of electronic systems. Recent advances in semiconductor-superconductor hybrid quantum dot arrays have allowed to realize degenerate quantum systems in a controllable way, e.g., allowing to observe robust zero-bias peaks in Kitaev chains, indicative for Majorana bound states. In this work, we conn… ▽ More The Fermi-Hubbard model and its rich phase diagram naturally emerges as a description for a wide range of electronic systems. Recent advances in semiconductor-superconductor hybrid quantum dot arrays have allowed to realize degenerate quantum systems in a controllable way, e.g., allowing to observe robust zero-bias peaks in Kitaev chains, indicative for Majorana bound states. In this work, we connect these two domains. Noting the strong on-site Coulomb repulsion within quantum dots, we study small arrays of spinful hybrid quantum dots implemented in a two-dimensional electron gas. This system constitutes a Fermi-Hubbard model with inter-site superconducting correlations. For two electronic sites, we find robust zero-bias peaks indicative of a strongly degenerate spectrum hosting emergent Majorana Kramers pairs or $\mathbb{Z}_3$-parafermions. Extending to three sites, we find that these spinful systems scale very differently compared to spinless Kitaev chains. When the sweet-spot conditions are satisfied pairwise, we find that the ground state degeneracy of the full three-site system is lifted. This degeneracy can be restored by tuning the superconducting phase difference between the hybrid segments. However, these states are not robust to quantum dot detuning. Our observations are a first step towards studying degeneracies in strongly interacting Fermi-Hubbard systems with superconducting correlations. △ Less

Submitted 15 December, 2025; originally announced December 2025.

Comments: 23 pages, 5 Main text figures, 9 Supplementary figures

Novel coupling between charge order and time-reversal-symmetry-breaking superconductivity

Authors: Quanxin Hu, Lingfeng Zhang, Yu Zheng, Yongwei Li, Qiheng Wang, Xinyu Liang, Baiqing Lv, Chi-Ming Yim, Takuto Kawakami, Vadim Grinenko, Xiao Hu, Hong Ding

Abstract: The interplay between charge-density waves (CDWs), which break translational symmetry, and spatially homogeneous superconductivity, which breaks global U(1) gauge symmetry, can give rise to an intriguing phenomenon: the pair-density wave, characterized by a spatial modulation of the superconducting order parameter. Yet how CDWs couple to unconventional superconducting states-particularly those wit… ▽ More The interplay between charge-density waves (CDWs), which break translational symmetry, and spatially homogeneous superconductivity, which breaks global U(1) gauge symmetry, can give rise to an intriguing phenomenon: the pair-density wave, characterized by a spatial modulation of the superconducting order parameter. Yet how CDWs couple to unconventional superconducting states-particularly those with time-reversal symmetry breaking (TRSB)-remains largely unexplored. Here, using scanning tunneling microscopy on heavily hole-doped Ba$_{1-x}$K$_x$Fe$_2$As$_2$, which hosts an s $\pm$ is superconducting state, we reveal a previously unobserved coupling between a surface CDW and TRSB superconductivity. Experimentally, the TRSB superconductivity imparts "chirality" to the CDW, which manifests as commensurate domains separated by domain walls with $π$-phase slips-forming what we term a bipolar CDW. The domain walls delineate TRSB domains of opposite chirality, consistent with spontaneous breaking of U(1) $\times$ Z2. Supported by theoretical modelling, we construct a framework in which a hidden interfacial pair-density modulation (PDM) mediates a linear coupling between the surface CDW and interband Josephson currents of TRSB superconductivity. Crucially, the theory shows that realizing this linear coupling requires a controlled global phase difference $δ$ $φ$ = $π$/2 between the PDM and CDW states. Our results uncover a previously overlooked connection between charge ordering and TRSB superconductivity, opening a pathway to explore intertwined quantum orders in iron-based superconductors and other strongly correlated systems. △ Less

Submitted 8 December, 2025; originally announced December 2025.

Comments: 34 pages, 14 figures

Accelerating discovery of infrared nonlinear optical materials with large shift current via high-throughput screening

Authors: Aiqin Yang, Dian Jin, Mingkang Liu, Daye Zheng, Qi Wang, Qiangqiang Gu, Jian-Hua Jiang

Abstract: Discovering nonlinear optical (NLO) materials with strong shift current response, particularly in the infrared (IR) regime, is essential for next-generation optoelectronics yet remains highly challenging in both experiments and theory, which still largely relies on case by case studies. Here, we employ a high-throughput screening strategy, applying a multi-step filter to the Materials Project data… ▽ More Discovering nonlinear optical (NLO) materials with strong shift current response, particularly in the infrared (IR) regime, is essential for next-generation optoelectronics yet remains highly challenging in both experiments and theory, which still largely relies on case by case studies. Here, we employ a high-throughput screening strategy, applying a multi-step filter to the Materials Project database (>154,000 materials), which yielded 2,519 candidate materials for detailed first-principle evaluation. From these calculations, we identify 32 NLO materials with strong shift current response ($σ$ > 100 $μA/V^2$). Our work reveals that layered structures with $C_{3v}$ symmetry and heavy $p$-block elements (e.g. Te, Sb) exhibit apparent superiority in enhancing shift current. More importantly, 9 of these compounds show shift current response peaks in the IR region, with the strongest reaching 616 $μA/V^2$, holding significant application potential in fields such as IR photodetection, sensing, and energy harvesting. Beyond identifying promising candidates, this work establishes a comprehensive and high-quality first-principles dataset for NLO response, providing a solid foundation for future AI-driven screening and accelerated discovery of high-performance NLO materials, as demonstrated by a prototype machine-learning application. △ Less

Submitted 4 December, 2025; originally announced December 2025.

Super-hard and superconducting boron clathrates in the prediction of U-B compounds

Authors: Juefei Wu, Dexi Shao, Junjie Wang, Yu Han, Bangshuai Zhu, Cuiying Pei, Qi Wang, Jian Sun, Yanpeng Qi

Abstract: The binary metal borides provide a promising platform for searching unique materials with superconductivity and super-hardness under high pressure, owing to the distinctive bonding characters of boron. In this work, combined the first-principles calculations and crystal structure predictions, we predicted 4 exotic stoichiometries and 8 unique U-B compounds under high pressure. The predicted compou… ▽ More The binary metal borides provide a promising platform for searching unique materials with superconductivity and super-hardness under high pressure, owing to the distinctive bonding characters of boron. In this work, combined the first-principles calculations and crystal structure predictions, we predicted 4 exotic stoichiometries and 8 unique U-B compounds under high pressure. The predicted compounds have layered or caged structure units and 4 of them host high hardness under ambient pressure. By removal of the U atoms, we predicted three meta-stable boron clathrates at ambient pressure. Remarkably, the Vickers hardness of the predicted C2/m-B6 is estimated to be 49-53 GPa, and the C2/m-B12 is superconducting with the Tc value of 16.12 K. Our calculations enrich the phase diagram of binary metal borides and boron allotropes, providing insights for the future theoretical and experimental studies on unique materials. △ Less

Submitted 3 December, 2025; originally announced December 2025.

Comments: 20 pages, 6 figures

Journal ref: Phys. Rev. Materials 9, 123601 (2025)

Dual instability of superconductivity from oxygen defects in La$_3$Ni$_2$O$_{7+δ}$

Authors: Peiheng Jiang, Jie Li, Yu-Han Cao, Xiaodong Cao, Zhicheng Zhong, Yi Lu, Qiang-Hua Wang

Abstract: We uncover a dual mechanism by which oxygen defects suppress superconductivity in the bilayer nickelate La$_3$Ni$_2$O$_{7+δ}$ using density functional theory, dynamical mean-field theory, and functional renormalization group analysis. Apical vacancies and interbilayer interstitials emerge as the dominant low-energy defect species and are further stabilized by orthorhombic domain walls. These two d… ▽ More We uncover a dual mechanism by which oxygen defects suppress superconductivity in the bilayer nickelate La$_3$Ni$_2$O$_{7+δ}$ using density functional theory, dynamical mean-field theory, and functional renormalization group analysis. Apical vacancies and interbilayer interstitials emerge as the dominant low-energy defect species and are further stabilized by orthorhombic domain walls. These two defect classes drive the electronic structure in opposing directions. Vacancy-induced disorder generates local magnetic moments and promotes Anderson localization at moderate concentrations, whereas periodic interstitial ordering yields a coherent but weakly correlated metallic background that fails to support superconductivity. These findings highlight the decisive role of oxygen defects in shaping the superconducting and provide microscopic guidance for improving superconductivity through controlled defect engineering. △ Less

Submitted 28 November, 2025; originally announced December 2025.

Perspective: Magnon-magnon coupling in hybrid magnonics

Authors: Wei Zhang, Yuzan Xiong, Jia-Mian Hu, Joseph Sklenar, Mitra Mani Subedi, M. Benjamin Jungfleisch, Vinayak S. Bhat, Yi Li, Luqiao Liu, Qiuyuan Wang, Yunqiu Kelly Luo, Youn Jue Bae, Benedetta Flebus

Abstract: The internal coupling of magnetic excitations (magnons) with themselves has created a new research sub-field in hybrid magnonics, i.e., magnon-magnon coupling, which focuses on materials discovery and engineering for probing and controlling magnons in a coherent manner. This is enabled by, one, the abundant mechanisms of introducing magnetic interactions, with examples of exchange coupling, dipola… ▽ More The internal coupling of magnetic excitations (magnons) with themselves has created a new research sub-field in hybrid magnonics, i.e., magnon-magnon coupling, which focuses on materials discovery and engineering for probing and controlling magnons in a coherent manner. This is enabled by, one, the abundant mechanisms of introducing magnetic interactions, with examples of exchange coupling, dipolar coupling, RKKY coupling, and DMI coupling, and two, the vast knowledge of how to control magnon band structure, including field and wavelength dependences of frequencies, for determining the degeneracy of magnon modes with different symmetries. In particular, we discuss how magnon-magnon coupling is implemented in various materials systems, with examples of magnetic bilayers, synthetic antiferromagnets, nanomagnetic arrays, layered van der Waals magnets, and (DMI SOT materials) in magnetic multilayers. We then introduce new concept of applications for these hybrid magnonic materials systems, with examples of frequency up/down conversion and magnon-exciton coupling, and discuss what properties are desired for achieving those applications. △ Less

Submitted 26 November, 2025; originally announced November 2025.

Comments: Comments and suggestions are welcome

Many-body electronic structure in pyrochlore superconductor CsBi2 and spin liquid Pr2Ir2O7

Authors: Wei Song, Guowei Liu, Hanbin Deng, Tianyu Yang, Yongkai Li, Xiao-Yu Yan, Ruoxing Liao, Qianming Wang, Jiayu Xu, Chao Yan, Yuanyuan Zhao, Hailang Qin, Da Wang, Wenchuan Jing, Dawei Shen, Kosuke Nakayama, Takafumi Sato, Chandan Setty, Desheng Wu, Boqing Song, Tianping Ying, Zhaoming Tian, Akito Sakai, Satoru Nakatsuji, Harish Kumar , et al. (4 additional authors not shown)

Abstract: The pyrochlore lattice materials can exhibit geometrical frustration, while the related many-body electronic states remain elusive. In this work, we performed scanning tunneling microscopy measurements on the pyrochlore superconductor CsBi2 and spin liquid Pr2Ir2O7 at 0.3 K. For the first time, we obtained atomically resolved images of their (111) surfaces, revealing a hexagonal lattice or a kagom… ▽ More The pyrochlore lattice materials can exhibit geometrical frustration, while the related many-body electronic states remain elusive. In this work, we performed scanning tunneling microscopy measurements on the pyrochlore superconductor CsBi2 and spin liquid Pr2Ir2O7 at 0.3 K. For the first time, we obtained atomically resolved images of their (111) surfaces, revealing a hexagonal lattice or a kagome lattice. Tunneling spectroscopy in CsBi2 reveals a nearly fully opened superconductivity gap. The ratio of 2Δ/kBTC = 4.7 suggests relatively strong coupling superconductivity, as compared with that in kagome superconductors AV3Sb5 (A = K, Rb, Cs). In contrast to the previous study categorizing CsBi2 as a type-I superconductor, the applied magnetic field induces a hexagonal vortex lattice in which each vortex core exhibits an intriguing three-fold symmetry state. In Pr2Ir2O7, we observed a spatially homogeneous Kondo-lattice resonance, which is compared with that in the kagome Kondo-lattice material CsCr6Sb6. We further discover that the Kondo resonance exhibits a spatial modulation with three-fold symmetry, and the applied magnetic field induces a Zeeman splitting of the Kondo resonance with intriguing atomic site dependence. We discuss the relations of these many-body electronic phenomena with the pyrochlore lattice geometry and its charge or spin frustration. Our systematic observations offer atomic-scale insights into the many-body electronic structures of the geometrically frustrated pyrochlore superconductors and spin liquids. △ Less

Submitted 22 November, 2025; originally announced November 2025.

Comments: To appear in PRB

Journal ref: Phys. Rev. B 112, 245131 2025

The Plastic Origin of van der Waals material GaGeTe

Authors: Qiao Wang, Ping-An Hu

Abstract: This work reports the discovery of high plasticity in ternary germanium-based single-crystal GaGeTe, which breaks through the inherent brittleness of traditional binary germanium-based chalcogenides and fills a research gap in germanium-based plastic semiconductors. Combining spherical aberration-corrected transmission electron microscopy experiments with density functional theory calculations, th… ▽ More This work reports the discovery of high plasticity in ternary germanium-based single-crystal GaGeTe, which breaks through the inherent brittleness of traditional binary germanium-based chalcogenides and fills a research gap in germanium-based plastic semiconductors. Combining spherical aberration-corrected transmission electron microscopy experiments with density functional theory calculations, the study reveals a novel deformation mechanism co-dominated by intralayer lattice distortion and interlayer slip. These findings provide fresh insight into the plastic behavior of inorganic semiconductors and clarifies the critical role of intralayer structural evolution in plastic behavior. This work not only expands the family of plastic semiconductor materials but also provides a new theoretical basis and candidate platform for the material design of flexible electronic devices. △ Less

Submitted 20 November, 2025; originally announced November 2025.

Interplay of spin-orbit coupling and trigonal crystal field enhances superconductivity in $LaAlO_3/KTaO_3$ (111)

Authors: Long Cheng, Jia Liu, Tongying Liu, Pan Chen, Mingyue Zhang, Jiashi Li, Shiyu Zhang, Fei Ye, Qing Wang, Weitao Liu, Jian Kang, Jiandi Zhang, Xiaofang Zhai

Abstract: In conventional superconductors, bulk physical properties typically degrade as the film thickness approaches the two-dimensional (2D) limit. Here in the (111) oriented LaAlO3/KTaO3 (LAO/KTO) heterostructure, we demonstrate experimental evidence that reducing the conducting layer thickness at the interface significantly enhances superconducting transition temperature Tc, in direct contrast to conve… ▽ More In conventional superconductors, bulk physical properties typically degrade as the film thickness approaches the two-dimensional (2D) limit. Here in the (111) oriented LaAlO3/KTaO3 (LAO/KTO) heterostructure, we demonstrate experimental evidence that reducing the conducting layer thickness at the interface significantly enhances superconducting transition temperature Tc, in direct contrast to conventional wisdom. From the sum frequency generation (SFG) spectroscopy and superconducting upper-critical field measurements, both the trigonal symmetry and spin orbit scattering are enhanced with the increased Tc. We attribute the enhanced superconductivity (SC) to the synergic interplay between spin-orbit coupling (SOC) and trigonal crystal field, resulting in an enhanced electron-phonon coupling. Furthermore, we show the existence of unconventional SC: the approaching linear temperature dependence of normal state resistance with increasing Tc and the existence of a quantum critical point (QCP) near the superconducting phase. Our findings provide important insight into the underlying mechanism of the strong orientation-dependent KTO interface SC. △ Less

Submitted 19 November, 2025; originally announced November 2025.

Chemical vapor deposition growth of continuous monolayer antiferromagnetic CrOCl films

Authors: Chao Chen, Yulu Liu, Hongyan Lu, Zihao Wang, Bowen Zheng, Qian Guo, Jingkuan Xiao, Ping Wang, Wanting Xu, Yulin Han, Mingxuan Chen, Xiaofan Cai, Jiabei Huang, Yaqing Han, Di Zhang, Renjun Du, Alexander S. Mayorov, Ziying Li, Shuai Zhang, Yi Huang, Tingting Cheng, Zhaolong Chen, Ronghua Liu, Nujiang Tang, Haibo Ni , et al. (7 additional authors not shown)

Abstract: The discovery of two-dimensional magnetic materials has provided an ideal platform for exploring physical phenomena in the two-dimensional limit. However, intrinsic two-dimensional antiferromagnetic materials have been rarely reported, limiting systematic studies of their electronic properties. The discovery of novel intrinsic two-dimensional antiferromagnets and the development of robust synthesi… ▽ More The discovery of two-dimensional magnetic materials has provided an ideal platform for exploring physical phenomena in the two-dimensional limit. However, intrinsic two-dimensional antiferromagnetic materials have been rarely reported, limiting systematic studies of their electronic properties. The discovery of novel intrinsic two-dimensional antiferromagnets and the development of robust synthesis strategies, therefore, remain significant challenges. Here, we report the chemical vapor deposition synthesis of CrOCl monolayer films and nanosheets that exhibit excellent air stability. The CrOCl morphology is tunable, ranging from two-dimensional nanosheets to three-dimensional flower-like structures, with lateral sizes ranging from several microns to continuous monolayer films. Structural characterization confirms the materials composition and high crystalline quality. Furthermore, magnetic measurements, supported by theoretical calculations, reveal a Néel temperature for CrOCl of ~14 K. This work provides a reliable route for preparing two-dimensional antiferromagnetic materials. △ Less

Submitted 18 November, 2025; originally announced November 2025.

Pressure-induced superconductivity in LaP2 with graphenelike phosphorus layer

Authors: Mingxin Zhang, Cuiying Pei, Bangshuai Zhu, Qi Wang, Juefei Wu, Yanpeng Qi

Abstract: Materials with graphene-like layers attract tremendous attention due to their electronic structures and superconducting properties. In this study, we synthesized LaP2 polycrystalline and observed a superconducting transition around 30 GPa. The critical temperature Tc increases monotonically with pressure, which is nearing saturation and reaches 7.8 K at 78 GPa. The synchrotron X-ray diffraction ex… ▽ More Materials with graphene-like layers attract tremendous attention due to their electronic structures and superconducting properties. In this study, we synthesized LaP2 polycrystalline and observed a superconducting transition around 30 GPa. The critical temperature Tc increases monotonically with pressure, which is nearing saturation and reaches 7.8 K at 78 GPa. The synchrotron X-ray diffraction experiments confirm the superconducting transition originates from a structure transition to the P6/mmm phase under high pressure, suggesting the observation of graphene-like phosphorus layers in transition metal phosphides. By first-principles calculations, we provide more evidence for the stability of the graphene-like phosphorus layers in LaP2. Our findings are helpful for the understanding of the LaP2 phase diagram under high pressure, and could shed light on the research of unique structures in transition metal phosphides under high pressure. △ Less

Submitted 17 November, 2025; originally announced November 2025.

Comments: 13 pages,5 figures

Journal ref: Physical Review B 112, 184108 (2025)

Impact of Electron Correlations on Infinite-Layer Cuprates and Nickelates

Authors: Xunyang Hong, Yuetong Wu, Ying Chan, Sze Tung Li, I. Biało, L. Martinelli, A. Drewanowski, Qiang Gao, Xiaolin Ren, Xingjiang Zhou, Zhihai Zhu, A. Galdi, D. G. Schlom, K. M. Shen, J. Choi, M. Garcia Fernandez, Ke-Jin Zhou, N. B. Brookes, H. M. Rønnow, Qisi Wang, J. Chang

Abstract: Optimization of unconventional superconductivity involves a balance of interaction strengths. Precise determination of correlation strength across different material families is therefore important. Here, we present a combined X-ray absorption spectroscopy (XAS) and resonant inelastic X-ray scattering (RIXS) study of infinite-layer PrNiO$_2$ and SrCuO$_2$ that enables fair comparison of their inte… ▽ More Optimization of unconventional superconductivity involves a balance of interaction strengths. Precise determination of correlation strength across different material families is therefore important. Here, we present a combined X-ray absorption spectroscopy (XAS) and resonant inelastic X-ray scattering (RIXS) study of infinite-layer PrNiO$_2$ and SrCuO$_2$ that enables fair comparison of their interaction strengths. For both compounds, we study the orbital and magnetic excitations and extract their dispersions along high-symmetry directions. Using a single-band Hubbard model and including higher-order exchange interactions, we derive the correlation factor $U/t$ for both compounds. A key finding is that despite a smaller Coulomb repulsion $U$, PrNiO$_2$ exhibits a correlation strength that is 20% stronger than that of its isostructural cuprate counterpart SrCuO$_2$. This indicates that a moderation of the correlation strength may further optimize superconductivity in nickelates. △ Less

Submitted 12 November, 2025; originally announced November 2025.

Comments: Supplementary information available upon request

Multiscale Dynamics of Roughness-Driven Flow in Soft Interfaces

Authors: Qian Wang, Suhaib Ardah, Tom Reddyhoff, Daniele Dini

Abstract: Soft lubricated contacts exhibit complex interfacial behaviours governed by the coupled effects of multiscale surface roughness and non-linear fluid-solid interactions. Accurately capturing this interplay across thin-film flows is challenging due to the strong synergy between contact mechanics and hydrodynamic flow, spanning over various spatiotemporal scales. Here, we develop a rigorous computati… ▽ More Soft lubricated contacts exhibit complex interfacial behaviours governed by the coupled effects of multiscale surface roughness and non-linear fluid-solid interactions. Accurately capturing this interplay across thin-film flows is challenging due to the strong synergy between contact mechanics and hydrodynamic flow, spanning over various spatiotemporal scales. Here, we develop a rigorous computational framework to simulate the frictional behaviour of soft lubricated interfaces; its modularity and the use of optimal solvers provides solutions for realistic configurations in lubrication regimes ranging from direct solid contact to complete fluid separation. Surface roughness is described via Persson's statistical theory as well as a deterministic Conjugate Gradient with Fast Fourier Transform (CG-FFT) approach, while limitations associated with classical half-space models are addressed by developing the Reduced Stiffness Method (RSM) to rigorously model pressure-induced surface responses. The integrated framework captures the full evolution of frictional behaviour, validated against experiments on rough elastomer-glass interfaces, revealing how surface roughness and material compliance together drive the transition from solid contact to fluid-mediated sliding. The developed approach establishes a robust and versatile simulation tool for analysing a plethora of soft interfacial systems shaped by fluid-solid interactions, with potential applications including but not limited to biomechanics, soft robotics and microfluidic systems. △ Less

Submitted 11 November, 2025; originally announced November 2025.

Contactless cavity sensing of superfluid stiffness in atomically thin 4Hb-TaS$_2$

Authors: Trevor Chistolini, Ha-Leem Kim, Qiyu Wang, Su-Di Chen, Luke Pritchard Cairns, Ryan Patrick Day, Collin Sanborn, Hyunseong Kim, Zahra Pedramrazi, Ruishi Qi, Takashi Taniguchi, Kenji Watanabe, James G. Analytis, David I. Santiago, Irfan Siddiqi, Feng Wang

Abstract: The exceptional tunability of two-dimensional van der Waals materials offers unique opportunities for exploring novel superconducting phases. However, in such systems, the measurement of superfluid phase stiffness, a fundamental property of a superconductor, is challenging because of the mesoscopic sample size. Here, we introduce a contact-free technique for probing the electrodynamic response, an… ▽ More The exceptional tunability of two-dimensional van der Waals materials offers unique opportunities for exploring novel superconducting phases. However, in such systems, the measurement of superfluid phase stiffness, a fundamental property of a superconductor, is challenging because of the mesoscopic sample size. Here, we introduce a contact-free technique for probing the electrodynamic response, and thereby the phase stiffness, of atomically thin superconductors using on-chip superconducting microwave resonators. We demonstrate this technique on 4Hb-TaS$_2$, a van der Waals superconductor whose gap structure under broken mirror symmetry is under debate. In our cleanest few-layer device, we observe a superconducting critical temperature comparable to that of the bulk. The temperature evolution of the phase stiffness features nodeless behavior in the presence of broken mirror symmetry, inconsistent with the scenario of nodal surface superconductivity. With minimal fabrication requirements, our technique enables microwave measurements across wide ranges of two-dimensional superconductors. △ Less

Submitted 28 October, 2025; originally announced October 2025.

Versatile tunable optical injection of chiral polarized Weyl fermions in a magnetic Weyl semimetal Co3Sn2S2

Authors: Zipu Fan, Junchao Ma, Jinying Yang, Yan Sun, Zhuocheng Lu, Shuxia Chen, Delang Liang, Dehong Yang, Chang Xu, Qinsheng Wang, Anlian Pan, Ji Feng, Enke Liu, JinLuo Cheng, Dong Sun

Abstract: Precise probe and control of various quantum degrees of freedom in novel quantum matter are central to understanding fundamental quantum physics and hold promise for innovative routes to encode and process information. Chirality is one such degree of freedom that has recently attracted intense research interest, especially for Weyl fermions in topological Weyl semimetals. The coupling of chiral de… ▽ More Precise probe and control of various quantum degrees of freedom in novel quantum matter are central to understanding fundamental quantum physics and hold promise for innovative routes to encode and process information. Chirality is one such degree of freedom that has recently attracted intense research interest, especially for Weyl fermions in topological Weyl semimetals. The coupling of chiral degrees of freedom through light-matter interactions and the versatile control of these couplings through external fields can lead to precise quantum control of Weyl fermions. In this work, we demonstrate the observation of light chirality-dependent photocurrent in the mid-infrared regime. Excitation wavelength-dependent measurements reveal that the photocurrent originates from the injection of chiral polarized Weyl fermions by chiral polarized mid-infrared photons. The optical process that generates unbalanced chiral polarized Weyl fermions is determined to be a third-order nonlinear photocurrent process. Compared with nonmagnetic Weyl semimetals, such coupling is versatilely tunable in magnetic Weyl semimetals with the magnetization direction and external electric field in addition to the chirality of light. Our results are not only directly applicable to tunable circular-polarization-sensitive photodetection in the mid-infrared regime, but also pave the way toward functional quantum devices that utilize the chiral quantum degrees of freedom of Weyl fermions. △ Less

Submitted 24 October, 2025; originally announced October 2025.

A transmon qubit realized by exploiting the superconductor-insulator transition

Authors: C. G. L. Bøttcher, E. Önder, T. Connolly, J. Zhao, C. Kvande, D. Q. Wang, P. D. Kurilovich, S. Vaitiekėnas, L. I. Glazman, H. X. Tang, M. H. Devoret

Abstract: Superconducting qubits are among the most promising platforms for realizing practical quantum computers. One requirement to create a quantum processor is nonlinearity, which in superconducting circuits is typically achieved by sandwiching a layer of aluminum oxide between two aluminum electrodes to form a Josephson junction. These junctions, however, face several limitations that hinder their scal… ▽ More Superconducting qubits are among the most promising platforms for realizing practical quantum computers. One requirement to create a quantum processor is nonlinearity, which in superconducting circuits is typically achieved by sandwiching a layer of aluminum oxide between two aluminum electrodes to form a Josephson junction. These junctions, however, face several limitations that hinder their scalability: the small superconducting gap of aluminum necessitates millikelvin operating temperatures, the material interfaces lead to dissipation, and the sandwich geometry adds unwelcome capacitance for high-frequency applications. In this work, we address all three limitations using a novel superconducting weak link based on the superconductor-insulator transition. By locally thinning a single film of niobium nitride, we exploit its thickness-driven superconductor-insulator transition to form a weak link employing only atomic layer deposition and atomic layer etching. We utilize our weak links to produce a transmon qubit, '$planaron$', with a measured anharmonicity of $α/2π= 235$ MHz; at present, the linewidth is $κ/2π= 15 \mathrm{\: MHz}$. The high superconducting gap of niobium nitride can enable operation at elevated temperatures in future devices, and the fully planar geometry of the weak link eliminates superfluous material interfaces and capacitances. The investigation of small patches of material near the SIT can shed new light on the nature of the transition, including the role of dissipation and finite-size effects. △ Less

Submitted 22 October, 2025; originally announced October 2025.

Comments: 9 pages, 5 figures

Phase-sensitive evidence for 2x2 pair density wave in a kagome superconductor

Authors: Xiao-Yu Yan, Guowei Liu, Hanbin Deng, Xitong Xu, Haiyang Ma, Hailang Qin, Jun-Yi Zhang, Yuanyuan Zhao, Haitian Zhao, Zhe Qu, Yigui Zhong, Kozo Okazaki, Xiquan Zheng, Yingying Peng, Zurab Guguchia, X. X. Wu, Qianghua Wang, X-H Fan, Wei Song, M-W Gao, Hendrik Hohmann, Matteo Durrnagel, Ronny Thomale, Jia-Xin Yin

Abstract: The pair-density-wave (PDW) exhibits periodic amplitude and sign modulations of the superconducting order parameter. Such a pairing state has been proposed to be sensitive to nonmagnetic scattering. In this work, we observe the nonmagnetic PDW-breaking effect in a kagome superconductor, using scanning tunneling microscopy. We observe 2x2 PDW induced by the coupling between charge order and superco… ▽ More The pair-density-wave (PDW) exhibits periodic amplitude and sign modulations of the superconducting order parameter. Such a pairing state has been proposed to be sensitive to nonmagnetic scattering. In this work, we observe the nonmagnetic PDW-breaking effect in a kagome superconductor, using scanning tunneling microscopy. We observe 2x2 PDW induced by the coupling between charge order and superconductivity. The global PDW is substantially suppressed upon doping the kagome lattice with dilute isovalent nonmagnetic impurities, whereas the charge order and uniform superconductivity remain robust. Spatial correlation analysis further confirms that PDW is distinctly suppressed near dopants. We attribute the PDW suppression to a nonmagnetic PDW breaking effect, arising from phase sign modulation of PDW in the kagome d-orbital hosting Bogoliubov Fermi states. △ Less

Submitted 12 October, 2025; originally announced October 2025.

Material Synthesis 2025 (MatSyn25) Dataset for 2D Materials

Authors: Chengbo Li, Ying Wang, Qianying Wang, Zhizhi Tan, Haiqing Jia, Yi Liu, Li Qian, Nian Ran, Jianjun Liu, Zhixiong Zhang

Abstract: Two-dimensional (2D) materials have shown broad application prospects in fields such as energy, environment, and aerospace owing to their unique electrical, mechanical, thermal and other properties. With the development of artificial intelligence (AI), the discovery and design of novel 2D materials have been significantly accelerated. However, due to the lack of basic theories of material synthesi… ▽ More Two-dimensional (2D) materials have shown broad application prospects in fields such as energy, environment, and aerospace owing to their unique electrical, mechanical, thermal and other properties. With the development of artificial intelligence (AI), the discovery and design of novel 2D materials have been significantly accelerated. However, due to the lack of basic theories of material synthesis, identifying reliable synthesis processes for theoretically designed materials is a challenge. The emergence of large language model offers new approaches for the reliability prediction of material synthesis processes. However, its development is limited by the lack of publicly available datasets of material synthesis processes. To address this, we present the Material Synthesis 2025 (MatSyn25), a large-scale open dataset of 2D material synthesis processes. MatSyn25 contains 163,240 pieces of synthesis process information extracted from 85,160 high-quality research articles, each including basic material information and detailed synthesis process steps. Based on MatSyn25, we developed MatSyn AI which specializes in material synthesis, and provided an interactive web platform that enables multifaceted exploration of the dataset (https://matsynai.stpaper.cn/). MatSyn25 is publicly available, allowing the research community to build upon our work and further advance AI-assisted materials science. △ Less

Submitted 1 October, 2025; originally announced October 2025.

BigBang-Proton Technical Report: Next-Word-Prediction is Scientific Multitask Learner

Authors: Hengkui Wu, Liujiang Liu, Jihua He, Qihao Wang, Keke Zhao, Shuyang Hu, Renle Fu, Dahao Liang, Lingyu Zeng, Bruce Liu, Yuan Liu, Jin Zhan, Jiaqiang Niu, Xinglong Jia, Yaqin Hu, Wenjun Ji, Panpan Chi, Ken Chen, Hengyuan Wu, Yingsi Xin, Yongfeng Zhu, Yuexin Wang, Manqi Ruan, Ningtao Bian, Xiaohua Wu , et al. (1 additional authors not shown)

Abstract: We introduce BigBang-Proton, a unified sequence-based architecture for auto-regressive language modeling pretrained on cross-scale, cross-structure, cross-discipline real-world scientific tasks to construct a scientific multi-task learner. BigBang-Proton incorporates three fundamental innovations compared to mainstream general-purpose LLMs: Theory-Experiment Learning paradigm aligns large-scale nu… ▽ More We introduce BigBang-Proton, a unified sequence-based architecture for auto-regressive language modeling pretrained on cross-scale, cross-structure, cross-discipline real-world scientific tasks to construct a scientific multi-task learner. BigBang-Proton incorporates three fundamental innovations compared to mainstream general-purpose LLMs: Theory-Experiment Learning paradigm aligns large-scale numerical experimental data with theoretical text corpora; Binary Patch Encoding replaces byte pair encoding(BPE) tokenization; Monte Carlo Attention substitutes traditional transformer architectures. Through next-word-prediction pretraining on cross-discipline scientific datasets of real-world problems mixed with general textual corpus, followed by fine-tuning and inference on downstream tasks, BigBang-Proton demonstrates 100\% accuracy in up to 50-digit arithmetic addition operations, performance on par with leading specialized models in particle physics jet tagging, matching MAE of specialized models in inter-atomic potential simulation, performance comparable to traditional spatiotemporal models in water quality prediction, and benchmark-exceeding performance in genome modeling. These results prove that language-guided scientific computing can match or exceed the performance of task-specific scientific models while maintaining multitask learning capabilities. We further hypothesize to scale the pretraining to the universe scale as a fundamental step toward developing material world foundational model. △ Less

Submitted 30 September, 2025; originally announced October 2025.

Comments: 93 pages, 39 figures

MSC Class: 68T05; 68T50; 00A69; 94A99 ACM Class: I.2.6; I.2.7; J.2; I.6.3; K.4.1

Observation of non-Hermitian topology in cold Rydberg quantum gases

Authors: Jun Zhang, Ya-Jun Wang, Shi-Yao Shao, Bang Liu, Li-Hua Zhang, Zheng-Yuan Zhang, Xin Liu, Chao Yu, Qing Li, Han-Chao Chen, Yu Ma, Tian-Yu Han, Qi-Feng Wang, Jia-Dou Nan, Yi-Ming Yin, Dong-Yang Zhu, Qiao-Qiao Fang, Dong-Sheng Ding, Bao-Sen Shi

Abstract: The pursuit of topological phenomena in non-Hermitian systems has unveiled new physics beyond the conventional Hermitian paradigm, yet their realization in interacting many-body platforms remains a critical challenge. Exploring this interplay is essential to understand how strong interactions and dissipation collectively shape topological phases in open quantum systems. Here, we experimentally dem… ▽ More The pursuit of topological phenomena in non-Hermitian systems has unveiled new physics beyond the conventional Hermitian paradigm, yet their realization in interacting many-body platforms remains a critical challenge. Exploring this interplay is essential to understand how strong interactions and dissipation collectively shape topological phases in open quantum systems. Here, we experimentally demonstrate non-Hermitian spectra topology in a dissipative Rydberg atomic gas and characterize parameters-dependent winding numbers. By increasing the interaction strength, the system evolves from Hermitian to non-Hermitian regime, accompanying emergence of trajectory loop in the complex energy plane. As the scanning time is varied, the spectra topology becomes twisted in the complex energy plane manifesting as a topology phase transition with the sign winding number changed. When preparing the system in different initial states, we can access a nontrivial fractional phase within a parameter space that globally possesses an integer winding. Furthermore, by changing the scanning direction, we observe the differentiated loops, revealing the breaking of chirality symmetry. This work establishes cold Rydberg gases as a versatile platform for exploring the rich interplay between non-Hermitian topology, strong interactions, and dissipative quantum dynamics. △ Less

Submitted 30 September, 2025; originally announced September 2025.

Quantum Zeno Effect in the Spatial Evolution of a Single Atom

Authors: Zheng-Yuan Zhang, Han-Chao Chen, Xin Liu, Li-Hua Zhang, Bang Liu, Shi-Yao Shao, Jun Zhang, Qi-Feng Wang, Qing Li, Yu Ma, Tian-Yu Han, Ya-Jun Wang, Dong-Yang Zhu, Jia-Dou Nan, Yi-Ming Yin, Qiao-Qiao Fang, Dong-Sheng Ding, Bao-Sen Shi

Abstract: The quantum Zeno effect (QZE) reveals that frequent measurements can suppress quantum evolution, but the detailed dynamics of the system under finite-duration measurements in experiments remain insufficiently explored. Here, we employ an optical dipole trap as a projective measurement to study the motion of a single cold atom in free space. By monitoring atomic loss, we directly observe the QZE in… ▽ More The quantum Zeno effect (QZE) reveals that frequent measurements can suppress quantum evolution, but the detailed dynamics of the system under finite-duration measurements in experiments remain insufficiently explored. Here, we employ an optical dipole trap as a projective measurement to study the motion of a single cold atom in free space. By monitoring atomic loss, we directly observe the QZE in single-atom motion in free space and find that the effect of dipole measurements on the atom comprises a short-time collapse followed by subsequent periodic unitary evolution, thereby providing an intuitive physical picture of measurement backaction across different timescales. We further investigate the effects of measurement frequency, strength, and spatial position, demonstrating that measurements not only suppress the spreading of quantum states but also enable deterministic preparation of distinct motional states. Furthermore, by dynamically controlling the measurement position, we achieve measurement-induced directional transport of a single atom without imparting additional momentum. Our results provide a direct experimental demonstration of the QZE in real space and establish a versatile framework for measurement-based control of atomic motion, paving the way for motional-state engineering in cold-atom platforms. △ Less

Submitted 29 September, 2025; originally announced September 2025.

Observation of Discrete Time Quasicrystal in Rydberg Atomic Gases

Authors: Dong-Yang Zhu, Zheng-Yuan Zhang, Qi-Feng Wang, Yu Ma, Tian-Yu Han, Chao Yu, Qiao-Qiao Fang, Shi-Yao Shao, Qing Li, Ya-Jun Wang, Jun Zhang, Han-Chao Chen, Xin Liu, Jia-Dou Nan, Yi-Ming Yin, Li-Hua Zhang, Guang-Can Guo, Bang Liu, Dong-Sheng Ding, Bao-Sen Shi

Abstract: Discrete time quasicrystals (DTQC) constitute a class of non-equilibrium matter characterized by temporal order without strict periodicity, in contrast to conventional time crystals. Investigating these phenomena is essential for expanding our fundamental understanding of far-from-equilibrium quantum matter and spontaneous symmetry breaking beyond periodic regimes. Here, we experimentally observe… ▽ More Discrete time quasicrystals (DTQC) constitute a class of non-equilibrium matter characterized by temporal order without strict periodicity, in contrast to conventional time crystals. Investigating these phenomena is essential for expanding our fundamental understanding of far-from-equilibrium quantum matter and spontaneous symmetry breaking beyond periodic regimes. Here, we experimentally observe a DTQC in a driven-dissipative ensemble of strongly interacting Rydberg atoms, displaying non-equilibrium dynamical response with a different finite Abelian group symmetry $\mathbb{Z}{_m} \times \mathbb{Z}{_n}$. By applying a quasi-periodic drive using a dual-frequency drive with incommensurate frequencies, we demonstrate that the system exhibits a robust subharmonic response at multiple incommensurate frequencies, signifying the emergence of a DTQC phase. We map the full phase diagram of the system, which includes the DTQC phase, and demonstrated its rigidity against perturbations in both RF field intensity and laser detuning. Moreover, we observe a cyclic group symmetry effect that constrains the construction of $\mathbb{Z}{_2} \times \mathbb{Z}{_3}$-symmetric DTQC. This work establishes a versatile platform for studying non-equilibrium phases of matter and provides insights into the dynamics of time-translation symmetry breaking in quantum many-body systems. △ Less

Submitted 25 September, 2025; originally announced September 2025.

All-magnonic neurons for analog artificial neural networks

Authors: David Breitbach, Moritz Bechberger, Hanadi Mortada, Björn Heinz, Roman Verba, Qi Wang, Carsten Dubs, Mario Carpentieri, Giovanni Finocchio, Davi Rodrigues, Alexandre Abbass Hamadeh, Philipp Pirro

Abstract: Analog neuromorphic hardware is gaining traction as conventional digital systems struggle to keep pace with the growing energy and scalability demands of modern neural networks. Here, we present analog, fully magnonic, artificial neurons, which exploit a nonlinear magnon excitation mechanism based on the nonlinear magnonic frequency shift. This yields a sharp trigger response and tunable fading me… ▽ More Analog neuromorphic hardware is gaining traction as conventional digital systems struggle to keep pace with the growing energy and scalability demands of modern neural networks. Here, we present analog, fully magnonic, artificial neurons, which exploit a nonlinear magnon excitation mechanism based on the nonlinear magnonic frequency shift. This yields a sharp trigger response and tunable fading memory, as well as synaptic connections to other neurons via propagating magnons. Using micro-focused Brillouin light scattering spectroscopy on a Gallium-substituted yttrium iron garnet thin film, we show multi-neuron triggering, cascadability, and multi-input integration across interconnected neurons. Finally, we implement the experimentally verified neuron activation function in a neural network simulation, yielding high classification accuracy on standard benchmarks. The results establish all-magnonic neurons as promising devices for scalable, low-power, wave-based neuromorphic computing, highlighting their potential as building blocks for future physical neural networks. △ Less

Submitted 22 September, 2025; originally announced September 2025.

Comments: 17 pages, 6 figures

A Strongly Anisotropic Superconducting Gap in the Kagome Superconductor CsV$_3$Sb$_5$: A Study of Directional Point-Contact Andreev Reflection Spectroscopy

Authors: Yu-qing Zhao, Zhi-fan Wu, Hai-yan Zuo, Weiming Lao, Wangju Yang, Qiuxia Chen, Yao He, Hai Wang, Qiangwei Yin, Qi Wang, Yang-peng Qi, Gang Mu, He-chang Lei, Cong Ren

Abstract: In the recently discovered V-based kagome superconductors AV$_3$Sb$_5$ (A = K, Rb, and Cs), superconductivity is intertwined with an unconventional charge density wave (CDW) order, raising a fundamental concern on the superconducting gap structure of such kagome superconductors in the presence of CDW orders. Here, we report directional soft point-contact Andreev reflection (SPCAR) spectroscopy mea… ▽ More In the recently discovered V-based kagome superconductors AV$_3$Sb$_5$ (A = K, Rb, and Cs), superconductivity is intertwined with an unconventional charge density wave (CDW) order, raising a fundamental concern on the superconducting gap structure of such kagome superconductors in the presence of CDW orders. Here, we report directional soft point-contact Andreev reflection (SPCAR) spectroscopy measurements on the kagome superconductor CsV$_3$Sb$_5$, revealing compelling evidence for the existence of a strongly anisotropic superconducting gap pairing state. The SPCAR spectra measured with current injected parallel to the $ab$-plane exhibit an in-gap single conductance peak, in contrast to those of SPCAR spectra: a double-peak structure in the perpendicular direction. These spectra are well described by an anisotropic single-gap BTK model. The extracted superconducting gaps comprise an isotropic large gap and a strongly anisotropic gap, originating from different Fermi surface sheets. Quantitative analysis reveals an anisotropy around $\ sim$70\% with a gap minimum of about 0.15 meV. These results shed new light on the unconventional multiband pairing states in kagome superconductors. △ Less

Submitted 7 September, 2025; originally announced September 2025.

Exchange spin-wave propagation in Ga:YIG nanowaveguides

Authors: Andrey A. Voronov, Khrystyna O. Levchenko, Roman Verba, Kristýna Davídková, Carsten Dubs, Michal Urbánek, Qi Wang, Dieter Suess, Claas Abert, Andrii V. Chumak

Abstract: Spin-wave-based computing has emerged as a promising approach to overcome the fundamental limitations of CMOS technologies. However, the increasing demand for device miniaturization down to a 100 nm scale presents significant challenges for long-distance spin-wave transport. Gallium-substituted yttrium iron garnet (Ga:YIG) offers a potential solution to these challenges due to its unique magnetic… ▽ More Spin-wave-based computing has emerged as a promising approach to overcome the fundamental limitations of CMOS technologies. However, the increasing demand for device miniaturization down to a 100 nm scale presents significant challenges for long-distance spin-wave transport. Gallium-substituted yttrium iron garnet (Ga:YIG) offers a potential solution to these challenges due to its unique magnetic properties. The reduced saturation magnetization in Ga:YIG enables efficient excitation of exchange-dominated spin waves, which exhibit enhanced transport characteristics compared to dipolar-dominated modes in conventional materials. Here, we present the first comprehensive study combining experimental, analytical, and numerical investigations of spin-wave propagation in Ga:YIG waveguides down to 145 nm width and 73 nm thickness. Using micro-focused Brillouin light scattering spectroscopy, TetraX simulations, and analytical dispersion calculations, we demonstrate that Ga:YIG waveguides support spin waves with significantly higher group velocities up to 600 m/s. This value remains constant for structures with different widths, leading to longer spin-wave propagation lengths in nanowaveguides compared to non-substituted YIG. These results reveal that gallium substitution provides access to faster and longer-lived spin waves, opening new possibilities for implementing this material in nanoscale magnonic devices. △ Less

Submitted 8 September, 2025; v1 submitted 5 September, 2025; originally announced September 2025.

Simulated Laser Cooling and Magneto-Optical Trapping of Group IV Atoms

Authors: Geoffrey Zheng, Jianwei Wang, Mohit Verma, Qian Wang, Thomas K. Langin, David DeMille

Abstract: We present a scheme for laser cooling and magneto-optical trapping of the Group IV (a.k.a. Group 14 or tetrel) atoms silicon (Si), germanium (Ge), tin (Sn), and lead (Pb). These elements each possess a strong Type-II transition ($J \rightarrow J' = J-1$) between the metastable $s^2p^2 \,^3 P_1$ state and the excited $s^2ps'\, ^3P_0^o$ state at an accessible laser wavelength, making them amenable t… ▽ More We present a scheme for laser cooling and magneto-optical trapping of the Group IV (a.k.a. Group 14 or tetrel) atoms silicon (Si), germanium (Ge), tin (Sn), and lead (Pb). These elements each possess a strong Type-II transition ($J \rightarrow J' = J-1$) between the metastable $s^2p^2 \,^3 P_1$ state and the excited $s^2ps'\, ^3P_0^o$ state at an accessible laser wavelength, making them amenable to laser cooling and trapping. We focus on the application of this scheme to Sn, which has several features that make it attractive for precision measurement applications. We perform numerical simulations of atomic beam slowing, capture into a magneto-optical trap (MOT), and subsequent sub-Doppler cooling and compression in a blue-detuned MOT of Sn atoms. We also discuss a realistic experimental setup for realizing a high phase-space density sample of Sn atoms. △ Less

Submitted 4 September, 2025; originally announced September 2025.

Comments: Main text: 11 pages, 7 figures, 5 tables. Supplemental material: 4 pages, 2 figures, 1 table

Experimental realization of dice-lattice flat band at the Fermi level in layered electride YCl

Authors: Songyuan Geng, Xin Wang, Risi Guo, Chen Qiu, Fangjie Chen, Qun Wang, Kangjie Li, Peipei Hao, Hanpu Liang, Yang Huang, Yunbo Wu, Shengtao Cui, Zhe Sun, Timur K. Kim, Cephise Cacho, Daniel S. Dessau, Benjamin T. Zhou, Haoxiang Li

Abstract: Flat electronic bands, where interactions among electrons overwhelm their kinetic energies, hold the promise for exotic correlation physics. The dice lattice has long been theorized as a host of flat bands with intriguing band topology. However, to date, no material has ever been found to host the characteristic flat bands of a dice lattice. Here, using angle-resolved photoemission spectroscopy (A… ▽ More Flat electronic bands, where interactions among electrons overwhelm their kinetic energies, hold the promise for exotic correlation physics. The dice lattice has long been theorized as a host of flat bands with intriguing band topology. However, to date, no material has ever been found to host the characteristic flat bands of a dice lattice. Here, using angle-resolved photoemission spectroscopy (ARPES), we discover a dice-lattice flat band at $E_F$ in the van der Waals (vdW) electride [YCl]$^{2+}$: 2e-. In this system, excess valence electrons from Y deconfine from the cation framework to form an interstitial anionic electron lattice that constitutes the dice lattice. Our ARPES measurements unambiguously identify two sets of dice-lattice bands in YCl, including a nearly dispersionless band at the Fermi level. The flat bands and other dispersive bands observed in ARPES find excellent agreement with first-principles calculations, and theoretical analysis reveals that the near-$E_F$ electronic structure is well captured by a simple dice-lattice model. Our findings thus end the long quest of a real dice flat band material and establish vdW electride YCl as a prototype of dice metals. Our results further demonstrate the anionic electron lattice as a novel scheme for realizing lattice geometries and electronic structures rare to find in conventional crystalline systems. △ Less

Submitted 28 August, 2025; originally announced August 2025.

Phase-engineered Non-degenerate Sliding Ferroelectricity Enables Tunable Photovoltaics in Monolayer Janus In2S2Se

Authors: Yixuan Li, Qiang Wang, Keying Han, Yitong Liang, Kai Kong, Yan Liang, Thomas Frauenheimc, Xingshuai Lv, Defeng Guo, Bin Wang

Abstract: Two-dimensional sliding ferroelectrics, with their enhanced efficiencies of charge separation and tunability, constitute promising platforms for next-generation photovoltaic devices. However, recent systems predominantly exhibit dual degenerate polarization states with weak intensity, hindering the optimal manipulations of photovoltaic effects through sliding ferroelectricity. Here, we address thi… ▽ More Two-dimensional sliding ferroelectrics, with their enhanced efficiencies of charge separation and tunability, constitute promising platforms for next-generation photovoltaic devices. However, recent systems predominantly exhibit dual degenerate polarization states with weak intensity, hindering the optimal manipulations of photovoltaic effects through sliding ferroelectricity. Here, we address this limitation by introducing two strengthened and distinct non-degenerate sliding ferroelectric phases (WZ' and ZB') in Janus In2S2Se, which can be achieved by Se-to-S substitution in monolayer In2Se3. First-principles calculations validate the experimental synthesis of this structure and its capability for reversible phase transitions triggered by atomic layer sliding, and a series of superior photovoltaic performances are demonstrated in such unique Janus In2S2Se, accompanied by a detailed analysis of how non-degenerate sliding ferroelectricity modulates distinct photovoltaic characteristics. The WZ' to ZB' transition can increase the carrier mobility and moderate the band gap while inducing an indirect-to-direct transition, yielding a marked red-shift and enhancement of the photocurrent peak in the infrared spectrum. Conversely, the WZ' phase, benefiting from enhanced polarization, delivers superior photoelectric conversion efficiency in the visible light region. This work establishes a phase-engineered framework of how non-degenerate sliding ferroelectricity orchestrates distinct photovoltaic behaviors, and the intrinsic physical correlations may offer novel perspectives for designing and regulating innovative photovoltaic devices. △ Less

Submitted 30 July, 2025; originally announced July 2025.

Influence of Built-in Electric Fields on the Optoelectronic and Catalytic Properties of Two-Dimensional Materials

Authors: Kai Kong, Qiang Wang, Yixuan Li, Yitong Liang

Abstract: In the realm of modern materials science and advanced electronics, ferroelectric materials have emerged as a subject of great intrigue and significance, chiefly due to their remarkable property of reversible spontaneous polarization. This unique characteristic is not just an interesting physical phenomenon; it plays a pivotal role in revolutionizing multiple technological applications, especially… ▽ More In the realm of modern materials science and advanced electronics, ferroelectric materials have emerged as a subject of great intrigue and significance, chiefly due to their remarkable property of reversible spontaneous polarization. This unique characteristic is not just an interesting physical phenomenon; it plays a pivotal role in revolutionizing multiple technological applications, especially in the domains of high-density data storage and the pursuit of fast device operation. In the past few decades, there has been a significant increase in the number of investigations and commercial applications proposed for ferroelectric materials. With the continuous miniaturization of electronic devices and the rapid development of two-dimensional (2D) materials, considerable efforts have been made towards exploring ferroelectricity in 2D materials, driven by the potential for revolutionary advancements in energy storage, data processing, and other emerging technologies. This exploration is fueled by the realization that 2D ferroelectric materials could offer unique properties such as high energy density, fast switching speeds, and scalability, which are crucial for the next generation of electronic devices. The out-of-plane (OOP) ferroelectricity exhibited by these 2D materials is generally more advantageous than the in-plane ferroelectricity, primarily because the vertical polarizability aligns more seamlessly with the requirements of most practical technological applications △ Less

Submitted 30 July, 2025; originally announced July 2025.

Comments: arXiv admin note: text overlap with arXiv:2306.15921

Magnetic Excitations of a Half-Filled Tl-based Cuprate

Authors: I. Biało, Q. Wang, J. Küspert, X. Hong, L. Martinelli, O. Gerguri, Y. Chan, K. von Arx, O. K. Forslund, W. R. Pudełko, C. Lin, N. C. Plumb, Y. Sassa, D. Betto, N. B. Brookes, M. Rosmus, N. Olszowska, M. D. Watson, T. K. Kim, C. Cacho, M. Horio, M. Ishikado, H. M. Rønnow, J. Chang

Abstract: Strong electron correlations drive Mott insulator transitions. Yet, there exists no framework to classify Mott insulators by their degree of correlation. Cuprate superconductors, with their tunable doping and rich phase diagrams, offer a unique platform to investigate the evolution of those interactions. However, spectroscopic access to a clean half-filled Mott-insulating state is lacking in compo… ▽ More Strong electron correlations drive Mott insulator transitions. Yet, there exists no framework to classify Mott insulators by their degree of correlation. Cuprate superconductors, with their tunable doping and rich phase diagrams, offer a unique platform to investigate the evolution of those interactions. However, spectroscopic access to a clean half-filled Mott-insulating state is lacking in compounds with the highest superconducting onset temperature. To fill this gap, we introduce a pristine, half-filled thallium-based cuprate system, Tl$_2$Ba$_5$Cu$_4$O$_{10+x}$ (Tl2504). Using high-resolution resonant inelastic x-ray scattering (RIXS), we probe long-lived magnon excitations and uncover a pronounced kink in the magnon dispersion, marked by a simultaneous change in group velocity and lifetime broadening. Modeling the dispersion within a Hubbard-Heisenberg approach, we extract the interaction strength and compare it with other cuprate systems. Our results establish a cuprate universal relation between electron-electron interaction and magnon zone-boundary dispersion. Superconductivity seems to be optimal at intermediate correlation strength, suggesting an optimal balance between localization and itinerancy. △ Less

Submitted 29 July, 2025; originally announced July 2025.

Comments: 10 pages, 5 figures, 2 tables

Persistent paramagnons in high-temperature infinite-layer nickelate superconductors

Authors: Yujie Yan, Ying Chan, Xunyang Hong, S. Lin Er Chow, Zhaoyang Luo, Yuehong Li, Tianren Wang, Yuetong Wu, Izabela Biało, Nurul Fitriyah, Saurav Prakash, Xing Gao, King Yau Yip, Qiang Gao, Xiaolin Ren, Jaewon Choi, Ganesha Channagowdra, Jun Okamoto, Xingjiang Zhou, Zhihai Zhu, Liang Si, Mirian Garcia-Fernandez, Ke-Jin Zhou, Hsiao-Yu Huang, Di-Jing Huang , et al. (3 additional authors not shown)

Abstract: The recent discovery of high-temperature superconductivity in hole-doped SmNiO$_2$, exhibiting the record-high transition temperature $T_c$ among infinite-layer (IL) nickelates, has opened a new avenue for exploring design principles of superconductivity. Experimentally determining the electronic structure and magnetic interactions in this new system is crucial to elucidating the mechanism behind… ▽ More The recent discovery of high-temperature superconductivity in hole-doped SmNiO$_2$, exhibiting the record-high transition temperature $T_c$ among infinite-layer (IL) nickelates, has opened a new avenue for exploring design principles of superconductivity. Experimentally determining the electronic structure and magnetic interactions in this new system is crucial to elucidating the mechanism behind the enhanced superconductivity. Here, we report a Ni $L$-edge resonant inelastic x-ray scattering (RIXS) study of superconducting Sm-based IL nickelate thin films Sm$_{1-x-y-z}$Eu$_x$Ca$_y$Sr$_z$NiO$_2$ (SECS). Dispersive paramagnonic excitations are observed in both optimally and overdoped SECS samples, supporting a spin-fluctuation-mediated pairing scenario. However, despite the two-fold enhancement of $T_c$ in the Sm-based nickelates compared to their Pr-based counterparts, the effective exchange coupling strength is reduced by approximately $20\%$. This behavior contrasts with hole-doped cuprates, where magnetic interactions correlate positively with $T_c$, highlighting essential differences in their superconducting mechanisms. △ Less

Submitted 24 July, 2025; originally announced July 2025.

Comments: Supplementary Information available upon request

Strain-Engineered Electronic Structure and Superconductivity in La$_3$Ni$_2$O$_7$ Thin Films

Authors: Yu-Han Cao, Kai-Yue Jiang, Hong-Yan Lu, Da Wang, Qiang-Hua Wang

Abstract: Recently, the films of the Ruddlesden-Popper (RP) nickelate superconductors, in which the (La,Pr)$_3$Ni$_2$O$_7$ system exhibits a remarkable transition temperature $T_c$ exceeding 40 K, were synthesized at ambient pressure. We systematically investigate the band structures and electronic correlation effect to identify the key factors controlling superconductivity and pathways to enhance $T_c$. Ba… ▽ More Recently, the films of the Ruddlesden-Popper (RP) nickelate superconductors, in which the (La,Pr)$_3$Ni$_2$O$_7$ system exhibits a remarkable transition temperature $T_c$ exceeding 40 K, were synthesized at ambient pressure. We systematically investigate the band structures and electronic correlation effect to identify the key factors controlling superconductivity and pathways to enhance $T_c$. Based on density functional theory (DFT) calculations, we construct a bilayer two-orbital ($3d_{3z^2-r^2}$ and $3d_{x^2-y^2}$) tight-binding model for a series of in-plane compression mimicking the substrate effect. We find the band energy at the $M$ point drops with the compression, leading to increase of the density of states at the Fermi level, in stark contrast to the behavior of the bulk under pressure. We then apply functional renormalization group (FRG) method to study the electronic correlation effect on the superconductivity. We find the $s_\pm$-wave pairing symmetry remains robust in the films, the same as the bulk. But somewhat surprisingly, for the films, we find $T_c$ can be enhanced by reducing the in-plane lattice constant, increasing the out-of-plane lattice constant, or further electron-doping. These findings are consistent with the itinerant picture of the superconductivity induced by spin-fluctuations and provide theoretical support for further boosting $T_c$ in future experiments. △ Less

Submitted 18 July, 2025; originally announced July 2025.

Comments: 5 pages, 5 figures

Quantum interference among vortex bound states in superconductors

Authors: Yi-Ming Fu, Da Wang, Qiang-Hua Wang

Abstract: In a recent experiment (Hou et al Phys. Rev. X 15, 011027), a new type of necklace-like vortex bound state (VBS) was observed and attributed to disorder induced interference among different Caroli-de Gennes-Matricon (CdGM) states within one single vortex. In this work, we further investigate the possibilities of quantum interference among the CdGM states from different vortices in clean supercondu… ▽ More In a recent experiment (Hou et al Phys. Rev. X 15, 011027), a new type of necklace-like vortex bound state (VBS) was observed and attributed to disorder induced interference among different Caroli-de Gennes-Matricon (CdGM) states within one single vortex. In this work, we further investigate the possibilities of quantum interference among the CdGM states from different vortices in clean superconductors, which may become significant near the upper critical field. We find a series of interference patterns in the local density of states (LDOS) due to the overlap between spatially separated individual CdGM states. On a vortex lattice, the interference can also lead to a necklace-like LDOS, hence, providing an alternative and intrinsic mechanism to observe the novel necklace-like, or other spatially modulated VBS more generally, in experiments. These results can be understood quite well within an effective tight-binding model constructed from the individual CdGM states, and can be checked in future experiments. △ Less

Submitted 13 July, 2025; originally announced July 2025.

Comments: 5 pages, 3 figures

Journal ref: New J. Phys. 27 073502 (2025)

Intriguing kagome topological materials

Authors: Qi Wang, Hechang Lei, Yanpeng Qi, Claudia Felser

Abstract: Topological quantum materials with kagome lattice have become the emerging frontier in the context of condensedmatter physics. Kagome lattice harbors strongmagnetic frustration and topological electronic states generatedby the unique geometric configuration.Kagomelattice has the peculiar advantages in the aspectsofmagnetism, topology aswell as strong correlationwhenthe spin, charge,ororbit degrees… ▽ More Topological quantum materials with kagome lattice have become the emerging frontier in the context of condensedmatter physics. Kagome lattice harbors strongmagnetic frustration and topological electronic states generatedby the unique geometric configuration.Kagomelattice has the peculiar advantages in the aspectsofmagnetism, topology aswell as strong correlationwhenthe spin, charge,ororbit degreesof free is introduced, and providing a promising platform for investigating the entangled interactionsamongthem. In this paper, we will systematically introduce the research progress on the kagome topological materials and give a perspective in the framework of the potential future development directions in this field. △ Less

Submitted 3 July, 2025; originally announced July 2025.

Comments: 5 pages, 1 figure

Journal ref: npj Quantum Materials (2025) 10:72

Josephson diode effect: a phenomenological perspective

Authors: Da Wang, Qiang-Hua Wang, Congjun Wu

Abstract: As a novel quantum phenomenon with nonreciprocal supercurrent, the Josephson diode effect was intensively studied in recent years. Here, we construct a generalized resistively capacitance shunted junction (RCSJ) model as a low-energy effective/phenomenological theory for a general Josephson junction. For the ideal diode effect defined by unequal critical currents $|I_{c+}|\ne|I_{c-}|$, both invers… ▽ More As a novel quantum phenomenon with nonreciprocal supercurrent, the Josephson diode effect was intensively studied in recent years. Here, we construct a generalized resistively capacitance shunted junction (RCSJ) model as a low-energy effective/phenomenological theory for a general Josephson junction. For the ideal diode effect defined by unequal critical currents $|I_{c+}|\ne|I_{c-}|$, both inversion $\mathcal{I}$ and time-reversal $\mathcal{T}$ symmetries are required to be broken. It can be further divided into two classes: intrinsic ($\mathcal{T}$-breaking for the junction itself) and extrinsic ($\mathcal{T}$-breaking under external current reversion). In addition, a pseudo diode effect ($\mathcal{T}$-breaking not necessary) can be defined by $|I_{c+}|=|I_{c-}|$ but unequal retrapping currents $|I_{r+}|\ne|I_{r-}|$, for which noise current is further shown to produce the diode feature effectively. Finally, when radio-frequency AC external current exists, the Shapiro steps appear and can be used to distinguish the above three types of the diode effect. Our work provides a unified framework for studying the Josephson diode effect and can be applied to design workable superconducting circuits incorporating the Josephson diode as a fundamental circuit element. △ Less

Submitted 29 June, 2025; originally announced June 2025.

Comments: 5 pages, 3 figures, 1 table

Diverse polymorphs and phase transitions in van der Waals In$_2$Se$_3$

Authors: Mingfeng Liu, Jiantao Wang, Peitao Liu, Qiang Wang, Zhibo Liu, Yan Sun, Xing-Qiu Chen

Abstract: Van der Waals In$_2$Se$_3$ has garnered significant attention due to its unique properties and wide applications associated with its rich polymorphs and polymorphic phase transitions. Despite extensive studies, the vast complex polymorphic phase space remains largely unexplored, and the underlying microscopic mechanism for their phase transformations remains elusive. Here, we develop a highly accu… ▽ More Van der Waals In$_2$Se$_3$ has garnered significant attention due to its unique properties and wide applications associated with its rich polymorphs and polymorphic phase transitions. Despite extensive studies, the vast complex polymorphic phase space remains largely unexplored, and the underlying microscopic mechanism for their phase transformations remains elusive. Here, we develop a highly accurate, efficient, and reliable machine-learning potential (MLP), which not only facilitates accurate exploration of the intricate potential energy surface (PES), but also enables us to conduct large-scale molecular dynamics (MD) simulations with first-principles accuracy. We identify the accurate structure of the $β''$ polymorph and uncover several previously unreported $β'$ polymorph variants exhibiting dynamic stability and competing energies, which are elucidated by characteristic flat imaginary phonon bands and the distinctive Mexican-hat-like PES in the $β$ polymorph. Through the MLP-accelerated MD simulations, we directly observe the polymorphic phase transformations among the $α$, $β$, $β'$, and $β''$ polymorphs under varying temperature and pressure conditions, and build for the first time an ab initio temperature-pressure phase diagram, showing good agreement with experiments. Furthermore, our MD simulations reveal a novel strain-induced reversible phase transition between the $β'$ and $β''$ polymorphs. This work not only unveils diverse polymorphs in van der Waals In$_2$Se$_3$, but also provides crucial atomic insights into their phase transitions, opening new avenues for the design of novel functional electronic devices. △ Less

Submitted 26 June, 2025; originally announced June 2025.

Comments: 32 pages, 20 figures (including Supplementary Information)

Resonances of recurrence time of monitored quantum walks

Authors: Ruoyu Yin, Qingyuan Wang, Sabine Tornow, Eli Barkai

Abstract: The recurrence time is the time a process first returns to its initial state. Using quantum walks on a graph, the recurrence time is defined through stroboscopic monitoring of the arrival of the particle to a node of the system. When the time interval between repeated measurements is tuned in such a way that eigenvalues of the unitary become degenerate, the mean recurrence time exhibits resonances… ▽ More The recurrence time is the time a process first returns to its initial state. Using quantum walks on a graph, the recurrence time is defined through stroboscopic monitoring of the arrival of the particle to a node of the system. When the time interval between repeated measurements is tuned in such a way that eigenvalues of the unitary become degenerate, the mean recurrence time exhibits resonances. These resonances imply faster mean recurrence times, which were recorded on quantum computers. The resonance broadening is captured by a restart uncertainty relation [R. Yin, Q. Wang, S. Tornow, E. Barkai, Proc. Natl. Acad. Sci. U.S.A. 122, e2402912121 (2025)]. To ensure a comprehensive analysis, we extend our investigation to include the impact of system size on the widened resonances, showing how the connectivity and energy spectrum structure of a system influence the restart uncertainty relation. Breaking the symmetry of the system, for example time-reversal symmetry breaking with a magnetic flux applied to a ring, removes the degeneracy of the eigenvalues of the unitary, hence modifying the mean recurrence time and the widening of the transitions, and this effect is studied in detail. The width of resonances studied here is related to the finite time resolution of relevant experiments on quantum computers, and to the restart paradigm. △ Less

Submitted 25 June, 2025; v1 submitted 24 June, 2025; originally announced June 2025.

Comments: 19 pages, 11 figures. Invited contribution for the Special Topic: Festschrift for Abraham Nitzan, of the Journal of Chemical Physics. Dedicated to the 80-th Brithday of Abraham Nitzan

Journal ref: J. Chem. Phys. 162, 244114 (2025)

Field-Free Superconducting Diode Enabled by Geometric Asymmetry and Perpendicular Magnetization

Authors: Jiaxu Li, Zijian Zhang, Shiqi Wang, Yu He, Haochang Lyu, Qiusha Wang, Bowen Dong, Daoqian Zhu, Hisakazu Matsuki, Dapeng Zhu, Guang Yang, Weisheng Zhao

Abstract: The superconducting diode effect (SDE)- manifested as directional, dissipationless supercurrents - is pivotal for realizing energy-efficient superconducting logic and memory technologies. Achieving high-efficiency SDE without external magnetic fields, however, remains a fundamental challenge. Here, we report a strongly enhanced, field-free SDE in Pt/Co/Nb heterostructures, enabled by the interplay… ▽ More The superconducting diode effect (SDE)- manifested as directional, dissipationless supercurrents - is pivotal for realizing energy-efficient superconducting logic and memory technologies. Achieving high-efficiency SDE without external magnetic fields, however, remains a fundamental challenge. Here, we report a strongly enhanced, field-free SDE in Pt/Co/Nb heterostructures, enabled by the interplay of engineered geometric asymmetry and stray fields from a perpendicularly magnetized Co layer. This configuration promotes directional vortex entry and spatially selective pinning, yielding diode efficiencies that exceed all previously reported field-free values. Temperature- and field-dependent transport measurements, supported by micromagnetic simulations, reveal that the enhanced nonreciprocity stems from three cooperative mechanisms: asymmetric vortex entry, localized magnetic pinning, and Lorentz-force imbalance. These findings establish a scalable, CMOS-compatible platform for high-performance superconducting rectifiers, offering new opportunities for cryogenic spintronics and quantum electronics. △ Less

Submitted 21 October, 2025; v1 submitted 21 June, 2025; originally announced June 2025.

1D YIG hole-based magnonic nanocrystal

Authors: K. O. Levchenko, K. Davídková, R. O. Serha, M. Moalic, A. A. Voronov, C. Dubs, O. Surzhenko, M. Lindner, J. Panda, Q. Wang, O. Wojewoda, B. Heinz, M. Urbánek, M. Krawczyk, A. V. Chumak

Abstract: Magnetic media with artificial periodic modulation-magnonic crystals (MCs) - enable tunable spin-wave dynamics and band structure engineering. Nanoscaling enhances these capabilities, making magnonic nanocrystals promising for both fundamental studies and applications. Here, we report on the design, fabrication, and characterization of one-dimensional YIG MCs with nanoholes ($d \approx $ 150 nm) s… ▽ More Magnetic media with artificial periodic modulation-magnonic crystals (MCs) - enable tunable spin-wave dynamics and band structure engineering. Nanoscaling enhances these capabilities, making magnonic nanocrystals promising for both fundamental studies and applications. Here, we report on the design, fabrication, and characterization of one-dimensional YIG MCs with nanoholes ($d \approx $ 150 nm) spaced $a \approx 1 μ$m apart. Micro-focused Brillouin light scattering and propagating spin-wave spectroscopy, supported by TetraX and MuMax$^3$ simulations, reveal spin-wave transmission over 5 $μ$m in the Damon-Eshbach configuration, and the formation of pronounced band gaps with rejection levels up to 26 dB. Detailed analysis of the spin-wave dispersion uncovered complex mode interactions, including two prominent anticrossings at 3.1 and 18.7 rad/$μ$m, between which the spin-wave energy is predominantly carried by the $n$ = 2 mode, enabling efficient transmission. The results advance the development of functional MCs and open pathways toward 2D magnonic nanoarrays and magnonic RF nanodevices. △ Less

Submitted 12 June, 2025; originally announced June 2025.

Comments: Manuscript: 6 pages, 4 figures; Supplementary materials: 12 pages, 11 figures

Evidence of Memory Effects in the Dynamics of Two-Level System Defect Ensembles Using Broadband, Cryogenic Transient Dielectric Spectroscopy

Authors: Qianxu Wang, Sara Magdalena Gómez, Juan S. Salcedo-Gallo, Roy Leibovitz, Jake Freeman, Simon A. Agnew, Salil Bedkihal, William J. Scheideler, Mattias Fitzpatrick

Abstract: Two-level system (TLS) defects in dielectrics cause decoherence in superconducting circuits, yet their origin, frequency distribution, and dipole moments remain poorly understood. Current probes, primarily based on qubits or resonators, require complex fabrication and measure defects only within narrow frequency bands and limited mode volumes, restricting insight into TLS behavior in isolated mate… ▽ More Two-level system (TLS) defects in dielectrics cause decoherence in superconducting circuits, yet their origin, frequency distribution, and dipole moments remain poorly understood. Current probes, primarily based on qubits or resonators, require complex fabrication and measure defects only within narrow frequency bands and limited mode volumes, restricting insight into TLS behavior in isolated materials and interfaces. We introduce Broadband Cryogenic Transient Dielectric Spectroscopy (BCTDS), a broadband 3D waveguide technique that enables probing of TLS ensembles at cryogenic temperatures. Complementary to the dielectric dipper method, this approach probes a broader spectrum and reveals interference of drive-induced sidebands in TLS ensembles. The broadband, power-tunable nature of BCTDS makes it well suited for studying dressed-state physics in driven TLS ensembles, including multi-photon processes and sideband-resolved dynamics. By analyzing Fourier-transformed time-domain signals, BCTDS reveals eigen-mode frequencies of undriven TLS ensembles through characteristic V-shaped features and uncovers memory effects arising from interactions and broadband excitation. The modular method can be applied throughout device fabrication, informing mitigation strategies and advancing the design of low-loss materials with broad implications for quantum technologies and materials science. △ Less

Submitted 18 November, 2025; v1 submitted 23 May, 2025; originally announced May 2025.

Comments: 18 pages, 13 figures

Pressure tuning of competing interactions on a honeycomb lattice

Authors: Piyush Sakrikar, Bin Shen, Eduardo H. T. Poldi, Faranak Bahrami, Xiaodong Hu, Eric M. Kenney, Qiaochu Wang, Kyle W. Fruhling, Chennan Wang, Ritu Gupta, Rustem Khasanov, Hubertus Luetkens, Stuart A. Calder, Adam A. Aczel, Gilberto Fabbris, Russell J. Hemley, Kemp W. Plumb, Ying Ran, Philipp Gegenwart, Alexander A. Tsirlin, Daniel Haskel, Michael J. Graf, Fazel Tafti

Abstract: Magnetic exchange interactions are mediated via orbital overlaps across chemical bonds. Thus, modifying the bond angles by physical pressure or strain can tune the relative strength of competing interactions. Here we present a remarkable case of such tuning between the Heisenberg (J) and Kitaev (K) exchange, which respectively establish magnetically ordered and spin liquid phases on a honeycomb la… ▽ More Magnetic exchange interactions are mediated via orbital overlaps across chemical bonds. Thus, modifying the bond angles by physical pressure or strain can tune the relative strength of competing interactions. Here we present a remarkable case of such tuning between the Heisenberg (J) and Kitaev (K) exchange, which respectively establish magnetically ordered and spin liquid phases on a honeycomb lattice. We observe a rapid suppression of the Neel temperature (TN) with pressure in Ag3LiRh2O6, a spin-1/2 honeycomb lattice with both J and K couplings. Using a combined analysis of x-ray data and first-principles calculations, we find that pressure modifies the bond angles in a way that increases the |K/J| ratio and thereby suppresses TN. Consistent with this picture, we observe a spontaneous onset of muon spin relaxation (muSR) oscillations below TN at low pressure, whereas in the high-pressure phase, oscillations appear only when T < TN/2. Unlike other candidate Kitaev materials, Ag3LiRh2O6 is tuned toward a quantum critical point by pressure while avoiding a structural dimerization in the relevant pressure range. △ Less

Submitted 23 May, 2025; originally announced May 2025.

Comments: 1 pdf, 3 figures, 1 table, published

Journal ref: Nature Communications 16, 4712 (2025)

Deeply Nonlinear Magnonic Directional Coupler

Authors: Xu Ge, Roman Verba, Philipp Pirro, Andrii V. Chumak, Qi Wang

Abstract: Dipolar coupling between closely spaced magnetic waveguides enables the design of magnonic directional couplers - universal devices capable of functioning as signal combiners, power splitters, demultiplexers, and more. The wavelength-dependent coupling, combined with the weak nonlinear variation of a spin wave's wavelength at constant-frequency, introduces power-dependent characteristics of direct… ▽ More Dipolar coupling between closely spaced magnetic waveguides enables the design of magnonic directional couplers - universal devices capable of functioning as signal combiners, power splitters, demultiplexers, and more. The wavelength-dependent coupling, combined with the weak nonlinear variation of a spin wave's wavelength at constant-frequency, introduces power-dependent characteristics of directional couplers. This property has been leveraged in the development of magnonic logic elements and other applications. Here, we explore another nonlinear phenomenon in a directional coupler arising purely from the nonlinear frequency shift of spin waves. We show that a strong nonlinear frequency shift causes the coupler to behave as if composed of nonidentical waveguides, suppressing the energy transfer between the waveguides. The transition from complete to negligible energy transfer exhibits a sharp threshold behavior, where the critical power is determined by the coupling strength and nonlinear frequency shift parameter. Based on these findings, a switchable directional coupler as a critical component for future integrated magnonic circuits is designed and validated by micromagnetic simulations. △ Less

Submitted 19 May, 2025; originally announced May 2025.

Comments: 14 pages, 4 figures

Active-Spin-State-Derived Descriptor for Hydrogen Evolution Reaction Catalysis

Authors: Yu Tan, Lei Li, Zi-Xuan Yang, Tao Huang, Qiao-Ling Wang, Tao Zhang, Jing-Chun Luo, Gui-Fang Huang, Wangyu Hu, Wei-Qing Huang

Abstract: Spin states are pivotal in modulating the electrocatalytic activity of transition-metal (TM)-based compounds, yet quantitatively evaluating the activity-spin state correlation remains a formidable challenge. Here, we propose an 'activity index n' as a descriptor, to assess the activity of the spin states for the hydrogen evolution reaction (HER). n descriptor integrates three key electronic parame… ▽ More Spin states are pivotal in modulating the electrocatalytic activity of transition-metal (TM)-based compounds, yet quantitatively evaluating the activity-spin state correlation remains a formidable challenge. Here, we propose an 'activity index n' as a descriptor, to assess the activity of the spin states for the hydrogen evolution reaction (HER). n descriptor integrates three key electronic parameters: the proportion (P), broadening range (R) and center cc of active spin state, which collectively account for the electronic structure modulation induced by both the intrinsic active site and its local coordination environment. Using 1T-phase ZrSe2-anchored TM atoms (TM=Sc to Ni) as prototypes, we reveal that the correlation between Gibbs free energy and the n value follows a linear relation, namely, the vGH reduces as the n decreases. Notably, ZrSe2-Mn exhibits the optimal n value (-0.56), corresponding the best HER activity with a vGH of 0.04 eV closer to the thermoneutral ideal value (0 eV) than even Pt (vGH = -0.09 eV). This relationship suggests that n is the effective descriptor of active spin state for HER of TM-based catalysts. Our study brings fundamental insights into the HER activity-spin state correlation, offering new strategies for HER catalyst design. △ Less

Submitted 19 May, 2025; originally announced May 2025.

Comments: 17 pages, 5 figures

Nonreciprocal spin waves in out-of-plane magnetized waveguides reconfigured by domain wall displacements

Authors: H. Mortada, R. Verba, Q. Wang, P. Pirro, A. Hamadeh

Abstract: Wave-based platforms for novel unconventional computing approaches like neuromorphic computing require a well-defined, but adjustable flow of wave information combined with non-volatile data storage elements to implement weights which allow for training and learning. Due to their inherent nonreciprocal properties and their direct physical interaction with magnetic data storage, spin waves are idea… ▽ More Wave-based platforms for novel unconventional computing approaches like neuromorphic computing require a well-defined, but adjustable flow of wave information combined with non-volatile data storage elements to implement weights which allow for training and learning. Due to their inherent nonreciprocal properties and their direct physical interaction with magnetic data storage, spin waves are ideal candidates to realize such platforms. In the present study, we show how spin-wave nonreciprocity induced by dipolar interactions of nanowaveguides with antiparallel, out-of-plane magnetization orientations can be used to create a spin-wave circulator allowing for unidirectional information transport and complex signal routing. In addition, the device can be reconfigured by a magnetic domain wall with adjustable position, which allows for a non-volatile tuning of the nonreciprocity and signal propagation. These properties are demonstrated for a spin-wave directional coupler through a combination of micromagnetic simulations and analytical modeling also showing that it functions as a waveguide crossing element, tunable power splitter, isolator, and frequency multiplexer. As magnetic material, out-of-plane magnetized Bismuth-doped Yttrium Iron Garnet has been considered. For this material, the motion of domain walls by magnonic spin transfer torque has been recently experimentally demonstrated which enables to store results from spin-wave computation. In combination with the presented concept of domain wall based reconfiguration and nonlinear spin-wave dynamics, this enables for the creation of a nano-scaled nonlinear wave computing platform with the capability for self-learning. △ Less

Submitted 15 May, 2025; originally announced May 2025.

Variational Quantum Monte Carlo investigations of the superconducting pairing in La$_3$Ni$_2$O$_7$

Authors: Yi-Qun Liu, Da Wang, Qiang-Hua Wang

Abstract: We investigate the pairing symmetry in the novel superconductor La$_3$Ni$_2$O$_7$ under pressure by the non-perturbative variational quantum Monte Carlo. Within the bilayer Hubbard model and extended $t-J$ model with two orbitals in the $E_g$ doublet, we find the local strong correlation triggers $s_\pm$-wave Cooper pairing, with sign change of the gap function among the various Fermi pockets, whi… ▽ More We investigate the pairing symmetry in the novel superconductor La$_3$Ni$_2$O$_7$ under pressure by the non-perturbative variational quantum Monte Carlo. Within the bilayer Hubbard model and extended $t-J$ model with two orbitals in the $E_g$ doublet, we find the local strong correlation triggers $s_\pm$-wave Cooper pairing, with sign change of the gap function among the various Fermi pockets, while the $d_{x^2-y^2}$-wave pairing is generically disfavored. This is in agreement with the results from functional renormalization group applied in the weak up to moderate correlation limit. We find the 3d$_{3z^2-r^2}$ orbital plays a leading role in the superconducting pairing. We also demonstrate the finite intra-orbital double occupancy even in the strong correlation limit, shedding light on the itinerant versus local moment picture of the electrons in this material. △ Less

Submitted 12 May, 2025; originally announced May 2025.

Comments: 9 pages, 7 figures

Journal ref: Phys. Rev. B 112, 014511 (2025)