Showing 1–50 of 163 results for author: Hou, Y

Reactive polar mesogenic self-assembly approach enables domain-programmable polymer ferroelectrics

Authors: Fan Ye, Minghui Deng, Yuyang Zheng, Xiujuan Liu, Xiuhu Zhao, Haowei Jiang, Yanyun Hou, Bingyu Zou, Neng-Ang Peng, Shuo Zhao, Kutay Sağdıç, Danqing Liu, Yang Shen, Yan-Qing Lu, Satoshi Aya, Mingjun Huang

Abstract: Ferroelectric polymers combine switchable polarization with the processability of soft materials, but their development has been dominated by poly(vinylidene fluoride) and related fluoropolymers, whose crystalline polar phases restrict mechanical compliance and domain design with spatial precision. Here we establish a generic design principle for creating intrinsically flexible ferroelectric liqui… ▽ More Ferroelectric polymers combine switchable polarization with the processability of soft materials, but their development has been dominated by poly(vinylidene fluoride) and related fluoropolymers, whose crystalline polar phases restrict mechanical compliance and domain design with spatial precision. Here we establish a generic design principle for creating intrinsically flexible ferroelectric liquid-crystal polymers through reactive polar mesogenic self-assembly. The approach creates polyfluoroalkyl-free polymer films in which robust ferroelectric order arises from liquid-crystalline molecular organization rather than crystalline phase formation. By transferring ferroelectric order from fluid mesogenic states into polymer networks, the resulting materials combine mechanical adaptability with programmable polar architectures. Especially, the photoalignment technology enables these polar states to be organized into pixelated domain architectures. This work establishes a design space towards soft ferroelectric polymers that integrate molecularly programmed polar order, mechanical tunability and environmentally conscious chemistry, expanding the design space of adaptive materials for flexible electronics, wearable systems and soft robotics. △ Less

Submitted 8 August, 2026; originally announced August 2026.

Quantum oscillation fingerprints of altermagnetism in hole-doped RuO2

Authors: Yuchi Yang, Yusheng Hou

Abstract: Altermagnetism, characterized by its ferromagnetism-like spin-splitting band structure and antiferromagnetism-like magnetic order, has garnered considerable attention recently. Although hole doping may promote magnetism in the debated altermagnet candidate RuO2, the evolution of its electronic and magnetic properties under hole doping remains poorly understood. Based on first-principles calculatio… ▽ More Altermagnetism, characterized by its ferromagnetism-like spin-splitting band structure and antiferromagnetism-like magnetic order, has garnered considerable attention recently. Although hole doping may promote magnetism in the debated altermagnet candidate RuO2, the evolution of its electronic and magnetic properties under hole doping remains poorly understood. Based on first-principles calculations, we employ quantum oscillations to study hole-doped RuO2. We find that hole doping can enhance spin splitting and reconstruct the Fermi surface in RuO2, which is revealed by the angle-dependent quantum oscillation frequency. By tracking a pair of closed Fermi-surface pockets, we identify a meaningful correlation between the magnetic moment of Ru and a quantum-oscillation-based signature of spin splitting. This correlation follows a quasi-linear trend over a broad doping range, which can be captured by a minimal two-dimensional d-wave altermagnetic model. In addition, the hole-doped RuO2 exhibits a transition from a nonmagnetic to an altermagnetic state via an intermediate state. The quasi-linear correlation through quantum oscillation and the distinct quantum oscillation frequency of the stable altermagnetic state can serve as useful signatures for identifying the altermagnetic state in RuO2. Our results provide a comprehensive framework for understanding hole-doped RuO2, offering new insights into altermagnetic transitions and their identification. △ Less

Submitted 27 July, 2026; originally announced July 2026.

Comments: Accepted for publication in Physical Review B. Main text: 9 pages, 5 figures; Supplemental Material: 7 pages, 8 figures

Journal ref: Phys. Rev. B 114, 123456 (2026)

A critical consideration of X-ray detectors based on Ga2O3: excitation, carrier transport mechanisms and performance standardization

Authors: Alfred Moore, Daniel A Lamb, Lijie Li, Oliver Fox, Kawal Sawhney, Ciaran Llewelyn, Jon E Evans, Saqib Rafique, Tiantian Chai, John Harrington, Zabeada Aslam, Andrew P Brown, Rik Drummond-Brydson, Yaonan Hou

Abstract: X-ray detection underpins a wide range of applications in medicine, security, industrial inspection, scientific research for non-destructive imaging and material analysis. The rapid development of Ga2O3-based X-ray detectors offers a promising pathway toward next-generation detectors with high sensitivity, low noise, and harsh environment applications, benefiting from its intrinsic material proper… ▽ More X-ray detection underpins a wide range of applications in medicine, security, industrial inspection, scientific research for non-destructive imaging and material analysis. The rapid development of Ga2O3-based X-ray detectors offers a promising pathway toward next-generation detectors with high sensitivity, low noise, and harsh environment applications, benefiting from its intrinsic material properties such as high density, wide band gap energy, and high thermal-chemical stability. However, the underlying device operating mechanisms, including both carrier excitation and transport processes, have not yet been adequately studied, largely due to the misuse of X-ray sources in previous studies. Besides, benchmarking of device characteristics has been problematic due to experimental or data analysis issues, as well as misunderstandings of the applied equations associated with parameter definitions. In this work, we have designed and performed an instructive research work based on epitaxial beta-Ga2O3:Si and its planar Schottky detectors, measured with energy-tuneable monochromatic X-ray beams on a synchrotron beamline, clarifying the device excitation and carrier transport mechanisms with properly benchmarked device performance. In the end, we propose a set of protocols for correctly measuring and analysing the device performance. The proposed protocols are broadly applicable and can be readily extended to other semiconductor X-ray detectors. △ Less

Submitted 14 July, 2026; originally announced July 2026.

Comments: 21 pages, 6 figures

From stable periodic orbits to many-body chaos: doubly tunable prethermalization via engineering of an emergent band structure

Authors: Jianan Wang, Yang Hou, Andrea Pizzi, Johannes Knolle, Roderich Moessner, Hongzheng Zhao

Abstract: We uncover a family of many-body periodic orbits in a periodically driven (Floquet) spin system away from the high-frequency limit. While linear stability analysis predicts that perturbed many-body trajectories remain close to stable periodic orbits, thermodynamic principles dictate that Floquet heating will ultimately set in. Our work aims to resolve the tension between these two expectations. In… ▽ More We uncover a family of many-body periodic orbits in a periodically driven (Floquet) spin system away from the high-frequency limit. While linear stability analysis predicts that perturbed many-body trajectories remain close to stable periodic orbits, thermodynamic principles dictate that Floquet heating will ultimately set in. Our work aims to resolve the tension between these two expectations. In particular, we show that perturbations away from the stable periodic orbits feature a description akin to a quasiparticle band structure. A long-lived prethermal regime appears when modes around the gapless point are slowly populated. The dispersion determines the prethermal lifetime, and we show how band engineering leads to a "doubly tunable" parametric dependence of the prethermal lifetime $R^{-W}$, with $R$ the width in momentum space of the quasiparticle distribution and $W$ the exponent of the dispersion around the gapless point. Our results not only establish a powerful route toward stabilizing non-equilibrium phases of matter in driven many-body systems but also establish a conceptual bridge between periodic orbits in 'low-dimensional' nonlinear systems and many-body chaos. △ Less

Submitted 14 July, 2026; originally announced July 2026.

Vortex Transport in Ni/Bi Bilayer Superconductor with Strong Spin-Orbit and Exchange Interaction

Authors: Laxmipriya Nanda, Sohini Guin, Yasen Hou, Rajib Sarkar, Naresh Shyaga, Souvik Banerjee, A. Sundaresan, N. S. Vidhyadhiraja, Jagadeesh S. Moodera, Dhavala Suri

Abstract: Nickel/bismuth (Ni/Bi) bilayers are a promising platform for exploring unconventional superconductivity. Ferromagnetic Ni is coupled to Bi, a strong spin orbit metal that only becomes superconducting below approx 10 mK, forming a bilayer exhibits superconductivity at a much higher temperatures, a Tc of 3 to 4 K. Such a bilayer thus makes an ideal system to probe Cooper pairing in strong spin orbit… ▽ More Nickel/bismuth (Ni/Bi) bilayers are a promising platform for exploring unconventional superconductivity. Ferromagnetic Ni is coupled to Bi, a strong spin orbit metal that only becomes superconducting below approx 10 mK, forming a bilayer exhibits superconductivity at a much higher temperatures, a Tc of 3 to 4 K. Such a bilayer thus makes an ideal system to probe Cooper pairing in strong spin orbit coupled magnetic environments. Magneto transport studies near Tc reveal the behavior of vortex dynamics and exchange proximity effects. It is seen that isolated vortices of the bilayers respond sensitively to out of plane fields, producing antisymmetric transverse resistance peaks attributable to competing Magnus and viscous forces. Control experiments using a ferromagnetic insulator confirm that superconductivity extends throughout the bilayer, not just confined at the interface. Overall, the results provide a unified picture of transport dominated by vortex dynamics and show that a conventional s wave order parameter accounts for the observations, with any likely unconventional contributions being only subtle. △ Less

Submitted 4 May, 2026; originally announced May 2026.

Evolution of the Saddle Point in Antimony Telluride Homologous Superlattices

Authors: Yi-Hsin Shen, Shane Smolenski, Ming Wen, Yimo Hou, Eoghan Downey, Jakob Hammond-Renfro, Katharine Moncrieffe, Chun Lin, Makoto Hashimoto, Donghui Lu, Kai Sun, Dominika Zgid, Emanuel Gull, Pierre Ferdinand P. Poudeu, Na Hyun Jo, Rachel S. Goldman

Abstract: Combining topological insulators with topological semimetals in the form of homologous superlattices is a promising approach for generating correlated quantum matter based upon Fermi level alignment with band extrema. For antimony telluride, a saddle point is predicted to occur at the M-point, while antimonene layering is predicted to move the M-point valence band towards the Fermi level. To date,… ▽ More Combining topological insulators with topological semimetals in the form of homologous superlattices is a promising approach for generating correlated quantum matter based upon Fermi level alignment with band extrema. For antimony telluride, a saddle point is predicted to occur at the M-point, while antimonene layering is predicted to move the M-point valence band towards the Fermi level. To date, the predicted saddle point at the M-point has not yet been demonstrated, and studies of antimony telluride homologous superlattices have been limited to one or two layers of antimonene added to antimony telluride. Here, we present scanning tunneling spectroscopy and angle-resolved photoemission spectroscopy studies of a series of antimony telluride homologous superlattices with two to four layers of antimonene. In addition to demonstrating the presence of a saddle point and associated van Hove singularity near the M-point, we identify the key role of Sb and Te $p_z$ orbital hybridization in driving the van Hove singularity toward the Fermi level. △ Less

Submitted 22 April, 2026; originally announced April 2026.

Proximity Magnetism in Mn(Bi,Sb)2Te4-(Bi,Sb)2Te3/MnTe Natural Heterostructures

Authors: Owen A. Vail, Shu-Wei Wang, Yasen Hou, Dinura Hettiarachchi, Jean-Felix Milette, Tim B. Eldred, Wenpei Gao, Wendy Sarney, Haile Ambaye, Jong Keum, Valeria Lauter, George J. de Coster, Matthew J. Gilbert, Don Heiman, Jagadeesh S. Moodera, Hang Chi

Abstract: Magnetic topological insulators and their heterostructures provide great opportunities in coupling band topology with nontrivial spin configuration for enhanced spintronic device performance as well as designing totally new magnetoelectric systems and functionalities. We find that Mn interdiffusion from MnTe when interfaced with (Bi,Sb)2Te3 stabilizes as self-organized Mn(Bi,Sb)2Te4 septuple lamel… ▽ More Magnetic topological insulators and their heterostructures provide great opportunities in coupling band topology with nontrivial spin configuration for enhanced spintronic device performance as well as designing totally new magnetoelectric systems and functionalities. We find that Mn interdiffusion from MnTe when interfaced with (Bi,Sb)2Te3 stabilizes as self-organized Mn(Bi,Sb)2Te4 septuple lamellae amongst alternating (Bi,Sb)2Te3 quintuple layers, as observed using scanning transmission electron microscopy and depth-sensitive polarized neutron reflectometry. We further demonstrate a valuable combination of magnetic and topological orders in these naturally formed Mn(Bi,Sb)2Te4-(Bi,Sb)2Te3 heterostructures that are exchange coupled with MnTe. Magnetotransport experiments and quantum magnetism simulations reveal that, above its own Neel temperature TN of 20 K, Mn(Bi,Sb)2Te4 mediates the exchange field leading to an anomalous Hall effect at the (Bi,Sb)2Te3/MnTe interface, with an enhanced interfacial TN exceeding 200 K. This novel magnetic interface in turn allows a robust and deterministic spin-orbit torque switching without an external magnetic field at a low critical current density of 300 kA cm-2. The antiferromagnetically coupled architecture of Mn(Bi,Sb)2Te4-(Bi,Sb)2Te3/MnTe, featuring unique magnetic and topological proximity effects across a chalcogenide backbone, is rich in fundamental interface physics and holds potential for practical applications in spintronics. △ Less

Submitted 20 April, 2026; originally announced April 2026.

Nonmagnetic-magnetic Transitions in Rutile RuO2

Authors: Yue-Fei Hou, Siyuan Liu, Wanxiang Fen, Jiajun Lu, Xinfeng Chen, Gui-Bin Liu, Ping Zhang

Abstract: Rutile RuO$_2$ has recently attracted great interest, as its magnetic ground state remains controversial. Experimental studies have reported either nonmagnetic (NM) or altermagnetic (AM) ground states in different crystalline samples of RuO$_2$, highlighting the need for a reasonable explanation to resolve this contradiction. In this study, density functional theory calculations are performed to r… ▽ More Rutile RuO$_2$ has recently attracted great interest, as its magnetic ground state remains controversial. Experimental studies have reported either nonmagnetic (NM) or altermagnetic (AM) ground states in different crystalline samples of RuO$_2$, highlighting the need for a reasonable explanation to resolve this contradiction. In this study, density functional theory calculations are performed to reveal the correlation-sensitive and strain-dependent magnetism of bulk RuO$_2$. On one hand, multiple AM phases with different magnitudes of the spin magnetic moment are identified in the Hubbard parameter space for RuO$_2$. On the other hand, when appropriate strains that significantly change the crystal cell volume are applied, the ground state of RuO$_2$ can undergo transitions between the NM state (with no spin splitting) and the magnetic states (with spin splitting in the band structure). These findings not only demonstrate intriguing physics in 4\textit{\textit{d}}-electron-correlated RuO$_2$, but also retain its potential for spintronic applications. △ Less

Submitted 4 June, 2026; v1 submitted 16 April, 2026; originally announced April 2026.

Comments: 20 pages, 6 figures

Nonmonotonic Evolution of the Superconducting Transition Temperature and Robust Multigap Extended s-wave + s-wave Pairing in Zn-Substituted FeSe Single Crystals

Authors: Han-Shu Xu, Changhao Ding, Guanyin Gao, Xin Zhang, Xinyu Yin, Xucai Kan, Jiaping Hu, Wen Xie, Wensen Wei, Yuxiao Hou, Keyu An, Haoxiang Li, Kaibin Tang, Yu-Yan Han

Abstract: We report a systematic study of superconductivity on Fe1-xZnxSe single crystals synthesized over a broad Zn doping range (x = 0-0.023). High-quality single crystals across all compositions range exhibit superconducting transitions, while the transition temperature Tc shows a pronounced nonmonotonic dependence on Zn doping concentration, indicating that the underlying mechanism govering Tc its evol… ▽ More We report a systematic study of superconductivity on Fe1-xZnxSe single crystals synthesized over a broad Zn doping range (x = 0-0.023). High-quality single crystals across all compositions range exhibit superconducting transitions, while the transition temperature Tc shows a pronounced nonmonotonic dependence on Zn doping concentration, indicating that the underlying mechanism govering Tc its evolution cannot be explained solely by simple impurity pair breaking alone. Magnetization and transport measurements confirm the bulk behavior of superconductivity and reveal enhanced scattering effects with Zn doping. Low-temperature specific heat is consistently described by a two-gap scenario composed of an isotropic s-wave gap and an anisotropic extended s-wave gap, whereas single-gap and alternative pairing symmetries fail to describe the data. The nearly unchanged relative weights of the two gap components suggest the weak interband scattering induced by Zn substitution, thereby preserving multiband superconductivity. These results demonstrate the robustness of multigap superconductivity in FeSe and impose stringent constraints on candidate pairing mechanisms, highlighting the role of multiband electronic structure and anisotropic gap formation. △ Less

Submitted 10 April, 2026; originally announced April 2026.

Comments: 16 pages,6 figures

Gate-tunable anisotropic Josephson diode effect in topological Dirac semimetal Cd$_3$As$_2$ nanowires

Authors: Yan-Liang Hou, An-Qi Wang, Na Li, Chun-Guang Chu, Alexander Brinkman, Zhi-Min Liao, Chuan Li

Abstract: The intrinsic Josephson diode effect (JDE) has recently attracted considerable attention due to its sensitivity to broken symmetries in Josephson junctions, offering a powerful probe for uncovering hidden symmetry-breaking mechanisms in materials. The presence of higher-harmonic components in the current-phase relation, together with spin-orbital coupling, makes topological materials ideal platfor… ▽ More The intrinsic Josephson diode effect (JDE) has recently attracted considerable attention due to its sensitivity to broken symmetries in Josephson junctions, offering a powerful probe for uncovering hidden symmetry-breaking mechanisms in materials. The presence of higher-harmonic components in the current-phase relation, together with spin-orbital coupling, makes topological materials ideal platforms to explore this effect. In this work, we present a systematic study of the JDE in type-I topological Dirac semimetal Cd$_3$As$_2$ nanowire-based Josephson junctions. We observe a pronounced gate-tunable and highly anisotropic diode response under different magnetic-field orientations. By developing a comprehensive phenomenological model, we capture the angular dependence of the diode effect and, through temperature-dependent measurements, disentangle the respective contributions from bulk and topological surface states. Notably, anomalies in the temperature dependence of the diode efficiency reveal the coexistence of multiple transport channels, highlighting the Josephson diode effect as a sensitive probe of hidden topological superconducting states. △ Less

Submitted 10 March, 2026; originally announced March 2026.

Magnetic anisotropic pinning and symmetric breaking induced by interfacial coupling in topological-like ruthenate superlattices

Authors: Zhongyuan Jiang, Zhiwei Zhang, Kesen Zhao, Wenjie Meng, Yuanyuan Zhao, Yubin Hou, Zhangzhang Cui, Jian Zhang, Zheling Shan, Haoliang Huang, Qingyou Lu, Yalin Lu

Abstract: Interfacial engineering enables various emergent effects such as spin reorientations and transport anisotropy. Noncollinear spin textures are essential for realizing many emergent quantum transport phenomena. However, driving such spin structures requires precise control of the interfacial magnetic coupling in complex oxide heterostructures. Here, by utilizing competing exchange interactions at th… ▽ More Interfacial engineering enables various emergent effects such as spin reorientations and transport anisotropy. Noncollinear spin textures are essential for realizing many emergent quantum transport phenomena. However, driving such spin structures requires precise control of the interfacial magnetic coupling in complex oxide heterostructures. Here, by utilizing competing exchange interactions at the interface between ferromagnetic metal SrRuO3 and ferromagnetic insulator LaCoO3, we discovered a noncollinear spin configuration in SrRuO3 sublayers. Magnetic stripes were induced by out-of-plane rather than in-plane magnetic fields, indicating strong anisotropy pinning in our superlattices. The observed magneto-transport anisotropy is well explained by our proposed spin configurations, accounting for contributions from both bulk and interface of the SrRuO3 layers. More interestingly, magnetic skymionic textures were absent even at high magnetic fields. The interfacial exchange interaction overwhelms the Dzyaloshinskii-Moriya interaction (DMI) that stabilizes skyrmions, featuring a higher exchange coupling energy than that for the topological spin textures. Our work highlights the potential of interfacial engineering in tuning the spintronic properties by designing proper interfacial interactions. △ Less

Submitted 25 February, 2026; originally announced February 2026.

Comments: 14 pages, 5 figures

Efficient and tunable narrowband second-harmonic generation by a large-area etchless lithium niobate metasurface

Authors: Yaping Hou, Yigong Luan, Yu Fan, Alfonso Nardi, Attilio Zilli, Bobo Du, Jinyou Shao, Marco Finazzi, Chunhui Wang, Lei Zhang, Michele Celebrano

Abstract: Optical resonances in nanostructures enable strong enhancement of nonlinear processes at the nanoscale, such as second-harmonic generation (SHG), with high-$Q$ modes providing intensified light--matter interactions and sharp spectral selectivity for applications in filtering, sensing, and nonlinear spectroscopy. Thanks to the recent advances in thin-film lithium niobate (TFLN) technology, these ke… ▽ More Optical resonances in nanostructures enable strong enhancement of nonlinear processes at the nanoscale, such as second-harmonic generation (SHG), with high-$Q$ modes providing intensified light--matter interactions and sharp spectral selectivity for applications in filtering, sensing, and nonlinear spectroscopy. Thanks to the recent advances in thin-film lithium niobate (TFLN) technology, these key features can be now translated to lithium niobate for realizing novel nanoscale nonlinear optical platforms. Here, we demonstrate a large-area metasurface, realized by scalable nanoimprint lithography, comprising a slanted titanium dioxide (TiO$_2$) nanograting on etchless TFLN for efficient narrowband SHG. This is enabled by the optimal coupling of quasi-bound state in the continuum (q-BIC) modes with a narrowband pulsed laser pump. The demonstrated normalized SHG efficiency is $0.15\%\,\mathrm{cm}^2/\mathrm{GW}$, which is among the largest reported for LN metasurfaces. The low pump peak intensity ($3.64~\mathrm{kW}/\mathrm{cm}^2$) employed, which enables SHG even by continuous-wave pumping, allows envisioning integrated and portable photonic applications. SHG wavelength tuning from $870$ to $920~\mathrm{nm}$ with stable output power as well as polarization control is also achieved by off-normal pump illumination. This versatile platform opens new opportunities for sensing, THz generation and detection, and ultrafast electro-optic modulation of nonlinear optical signals. △ Less

Submitted 3 February, 2026; v1 submitted 31 January, 2026; originally announced February 2026.

Comments: 17 pages, 5 figures

Topological-transition-driven Giant Enhancement of Second-harmonic Generation in Ferroelectric Bismuth Monolayer

Authors: Wen-Zheng Chen, Hongjun Xiang, Yusheng Hou

Abstract: The interplay between band topology and light in condensed materials could unlock intriguing nonlinear optical phenomena, enabling modern photonic technologies such as quantum light sources and sub-wavelength topological lasers. Here, we unveil that a buckling-tuned topological transition in ferroelectric bismuth monolayer unleashes a giant second-harmonic generation. Using first-principles calcul… ▽ More The interplay between band topology and light in condensed materials could unlock intriguing nonlinear optical phenomena, enabling modern photonic technologies such as quantum light sources and sub-wavelength topological lasers. Here, we unveil that a buckling-tuned topological transition in ferroelectric bismuth monolayer unleashes a giant second-harmonic generation. Using first-principles calculations, we surprisingly find that ferroelectric bismuth monolayer with a buckling parameter, $Δh$, has a large susceptibility $χ^{(2)}$ on the order of $10^{7}$ $\mathrm{pm}^2/\mathrm{V}$, exceeding monolayer MoS$_2$ by about two orders of magnitude. When $Δh$ is engineered to the critical window where Dirac electrons emerge, a low-frequency resonance appears, boosting $χ^{(2)}$ by an additional order of magnitude. We show that this enhancement is localized on the Dirac cones and dominated by intraband modification contributions. Based on an extended Dirac model, we establish that this enhancement physically originates from the ultralight effective masses $m^{*}$ of Dirac electrons through scaling with the Fermi velocity $v_F$ and band gap $E_g$. Our findings provide a general paradigm for achieving exceptional second-harmonic generation via engineering topological criticality, and could serve as an experimental signature of Dirac electrons in topological materials. △ Less

Submitted 6 March, 2026; v1 submitted 28 January, 2026; originally announced January 2026.

Comments: 18 pages; 4 figures; Added references in section 1;

Magnetic field-induced non-trivial Lifshitz transition in TaCo2Te2

Authors: Suman Kalyan Pradhan, Xiaoming Ma, Jicheng Wang, Weiqi Liu, Yue Dai, Wenxing Chen, Xiaobai Ma, Wenyun Yang, Yu Wu, Zhaochu Luo, Raktim Datta, Arnab Bera, Samik DuttaGupta, Jinbo Yang, Yanglong Hou, Chang Liu, Rui Wu

Abstract: Magnetic-field-driven Lifshitz transitions are typically considered zero-temperature phenomena involving Fermi-surface reconstruction without symmetry breaking. Here, we report an unconventional Lifshitz transition in TaCo2Te2 that emerges exclusively within a narrow finite-temperature window under cooperative tuning by both temperature and magnetic field. Bulk-sensitive transport and thermoelectr… ▽ More Magnetic-field-driven Lifshitz transitions are typically considered zero-temperature phenomena involving Fermi-surface reconstruction without symmetry breaking. Here, we report an unconventional Lifshitz transition in TaCo2Te2 that emerges exclusively within a narrow finite-temperature window under cooperative tuning by both temperature and magnetic field. Bulk-sensitive transport and thermoelectric measurements demonstrate continuous Fermi-surface renormalization at low temperatures, where the transition is sharply triggered by a critical magnetic field. Crucially, neutron diffraction reveals the absence of structural or magnetic phase transitions, while angle-resolved photoemission spectroscopy shows no spectral anomalies in electronic structure without magnetic field. These observations constrain the mechanism to a Zeeman-driven process invisible to equilibrium probes, establishing a paradigm where Fermi-surface topology is jointly controlled by temperature and magnetic field. △ Less

Submitted 26 January, 2026; originally announced January 2026.

Comments: 4 figures

Magnetic exchange coupled nonreciprocal devices for cryogenic memory

Authors: Josep Ingla-Aynés, Lina Johnsen Kamra, Franklin Dai, Yasen Hou, Shouzhuo Yang, Peng Chen, Oleg A. Mukhanov, Jagadeesh S. Moodera

Abstract: As computing power demands continue to grow, superconducting electronics present an opportunity to reduce power consumption by increasing the energy efficiency of digital logic and memory. A key milestone for scaling this technology is the development of efficient superconducting memories. Such devices should be nonvolatile, scalable to high integration density and memory capacity, enable fast and… ▽ More As computing power demands continue to grow, superconducting electronics present an opportunity to reduce power consumption by increasing the energy efficiency of digital logic and memory. A key milestone for scaling this technology is the development of efficient superconducting memories. Such devices should be nonvolatile, scalable to high integration density and memory capacity, enable fast and low-power reading and writing operations, and be compatible with the digital logic. We present a versatile device platform to develop such nonvolatile memory devices consisting of an exchange-coupled ultra-thin superconductor encapsulated between two ferromagnetic insulators (FIs). The superconducting exchange coupling, which is tuneable by the relative alignment between the FI magnetizations, enables the switching of superconductivity on and off. We exploit this mechanism to create a superconducting nonvolatile memory where single-cell writing is realized using heat-assisted magnetic recording, and explain how it can become a contender for state-of-the-art superconducting memories. Furthermore, below their critical temperatures, the memory elements show a marked nonreciprocity, with zero magnetic field superconducting diode efficiencies exceeding $\pm$60%, showing the versatility of the proposed devices for superconducting computing. △ Less

Submitted 10 January, 2026; originally announced January 2026.

Comments: 8 pages, 4 figures

High-Performance KV$_3$Sb$_5$/WSe$_2$ van der Waals Photodetectors

Authors: Yang Yang, Shaofeng Rao, Yuxuan Hou, Jiabo Liu, Deng Hu, Yufei Guo, Jianzhou Zhao, Hechen Ren, Zhiwei Wang, Fan Yang

Abstract: Kagome metals AV$_3$Sb$_5$ (A = K, Rb, Cs) have recently emerged as a promising platform for exploring correlated and topological quantum states, yet their potential for optoelectronic applications remains largely unexplored. Here, we report high-performance photodetectors based on van der Waals KV$_3$Sb$_5$/WSe$_2$ heterojunctions. A high-quality Schottky interface readily forms between KV$_3$Sb… ▽ More Kagome metals AV$_3$Sb$_5$ (A = K, Rb, Cs) have recently emerged as a promising platform for exploring correlated and topological quantum states, yet their potential for optoelectronic applications remains largely unexplored. Here, we report high-performance photodetectors based on van der Waals KV$_3$Sb$_5$/WSe$_2$ heterojunctions. A high-quality Schottky interface readily forms between KV$_3$Sb$_5$ and WSe$_2$, enabling efficient separation and transport of photoinduced carriers. Under 520 nm illumination, the device achieves an open-circuit voltage up to 0.6 V, a responsivity of 809 mA/W, and a fast response time of 18.3 us. This work demonstrates the promising optoelectronic applications of Kagome metals and highlights the potential of KV$_3$Sb$_5$-based van der Waals heterostructures for high-performance photodetection. △ Less

Submitted 5 January, 2026; v1 submitted 30 December, 2025; originally announced December 2025.

Comments: 16 pages including Supporting Information

Deciphering the lattice vibrational behaviors of CuInP2S6 by angle-resolved polarized Raman scattering

Authors: Yiqi Hu, Jun-Jie Zhang, Zhou Zhou, Shun Wang, Qiankun Li, Yanfei Hou, Tianhao Ying, Lingling Yang, Jingyao Zhang, Shuzhong Yin, Yuyan Weng, Shuai Dong, Jianlin Yao, Liang Fang, Lu You

Abstract: The layered van der Waals (vdW) ferroelectric CuInP2S6 (CIPS) exhibits unique cation hopping-driven phenomena that bring about unconventional properties with intriguing mechanisms and hold promises for advanced applications in nanoelectronics. However, an explicit analysis of its lattice dynamics and vibrational symmetries, pivotal for understanding the material's peculiar ferroelectric and ferroi… ▽ More The layered van der Waals (vdW) ferroelectric CuInP2S6 (CIPS) exhibits unique cation hopping-driven phenomena that bring about unconventional properties with intriguing mechanisms and hold promises for advanced applications in nanoelectronics. However, an explicit analysis of its lattice dynamics and vibrational symmetries, pivotal for understanding the material's peculiar ferroelectric and ferroionic behaviors, remains incomplete. Here, we employ angle-resolved polarized Raman spectroscopy in concert with first-principles calculations to systematically unravel the anisotropic lattice vibrations of CIPS single crystals. By analyzing the polarization-dependent Raman intensities, we determine the symmetry assignments and Raman tensors of all major vibrational modes, revealing good agreement with theoretical predictions. Furthermore, we demonstrate the utility of Raman spectroscopy as a sensitive and non-invasive probe for structural and ferroelectric order evolution, by examining temperature-driven phase transitions and thickness-dependent polarization suppression in CIPS. Our findings establish a foundational framework for correlating lattice dynamics with functional properties in CIPS and provide a methodological blueprint for studying other vdW ferroelectrics. △ Less

Submitted 23 December, 2025; originally announced December 2025.

Comments: Supplementary Table S2 with detialed displacement patterns of major vibrational modes (gif figures) can be found in Figshare (10.6084/m9.figshare.30944357)

Journal ref: Chinese Phys. Lett. 42 120805 (2025)

Electronic Phonons in a Moiré Electron Crystal

Authors: Yan Zhao, Yuhang Hou, Xiangbin Cai, Shihao Ru, Shunshun Yang, Yan Zhang, Xuran Dai, Qiuyu Shang, Abdullah Rasmita, Haiyang Pan, Kenji Watanabe, Takashi Taniguchi, Hongbin Cai, Hongyi Yu, Weibo Gao

Abstract: Collective quantum phenomena, such as the excitation of composite fermions1, spin waves2, and exciton condensation3,4, can emerge in strongly correlated systems like the fractional quantum Hall states5, spin liquids6, or excitonic insulators7. Two-dimensional (2D) moiré superlattices have emerged as a powerful platform for exploring such correlated phases and their associated collective excitation… ▽ More Collective quantum phenomena, such as the excitation of composite fermions1, spin waves2, and exciton condensation3,4, can emerge in strongly correlated systems like the fractional quantum Hall states5, spin liquids6, or excitonic insulators7. Two-dimensional (2D) moiré superlattices have emerged as a powerful platform for exploring such correlated phases and their associated collective excitations8,9. Specifically, electron crystals stabilized by longrange Coulomb interactions may host collective vibrational excitations emerging from electron correlations10, termed electronic phonons, which are fundamentally distinct from atomic lattice phonons. Despite theoretical prediction of their existence in moiré electron crystals11, direct experimental evidence has remained elusive. Here we report the observation of electronic phonons in the Mott insulating and stripe phases of a WS2/WSe2 moiré superlattice, achieved through light scattering measurements. The phonon energies, temperature and filling factor dependencies, along with theoretical modeling, corroborate their origin as collective vibrations of a correlated electron crystal. Polarization-resolved measurements further indicate rotational symmetry breaking in the Mott state. Notably, these electronic phonons exhibit strong tunability in energy, intensity, and polarization under external electric or magnetic fields, highlighting rich and controllable lattice dynamics of the electron crystal. These findings provide direct spectroscopic evidence for the electronic crystalline nature of correlated phases, opening avenues for probing and manipulating collective excitations in correlated electron systems. △ Less

Submitted 20 December, 2025; originally announced December 2025.

Comments: 31 pages, 4 main figures, 9 extended data figures

Unidirectional magnetoresistance driven by nonequilibrium antiferromagnetic magnons

Authors: Xue He, Hans Gløckner Giil, Caiqiong Xu, Jicheng Wang, Arne Brataas, Jinbo Yang, Yanglong Hou, Rui Wu, Shilei Ding

Abstract: Magnetoresistive effects are typically symmetric under magnetization reversal. However, nonlinear spin transport can give rise to unidirectional magnetoresistance in systems with strong spin-orbit interaction and broken inversion symmetry. Here, we demonstrate that the nonequilibrium magnon accumulation characterized by a finite magnon chemical potential can lead to a large and robust magnonic uni… ▽ More Magnetoresistive effects are typically symmetric under magnetization reversal. However, nonlinear spin transport can give rise to unidirectional magnetoresistance in systems with strong spin-orbit interaction and broken inversion symmetry. Here, we demonstrate that the nonequilibrium magnon accumulation characterized by a finite magnon chemical potential can lead to a large and robust magnonic unidirectional spin Hall magnetoresistance (USMR) in the weakly coupled van der Waals antiferromagnet CrPS4 in contact with Pt. Unlike conventional magnonic USMR driven by magnetization fluctuations, this effect persists under strong magnetic fields and low temperatures, with a pronounced peak near the spin-flip transition. The magnitude of magnonic USMR in CrPS4/Pt exceeds that of YIG/Pt by more than two orders of magnitude and surpasses the electrical USMR in metallic Ta/Co bilayers by a factor of two. The observed field and temperature dependence indicates that spin transport is dominated by magnon chemical potential gradients rather than thermal- or fluctuation-driven magnon generation. These findings establish a new mechanism for nonlinear magnetoresistance in antiferromagnetic van der Waals heterostructures and open a route to magnon-based antiferromagnetic spintronic functionalities in two-terminal device geometries. △ Less

Submitted 28 January, 2026; v1 submitted 12 December, 2025; originally announced December 2025.

Comments: 21 pages, 4 figures

Learning Thermoelectric Transport from Crystal Structures via Multiscale Graph Neural Network

Authors: Yuxuan Zeng, Wei Cao, Yijing Zuo, Fang Lyu, Wenhao Xie, Tan Peng, Yue Hou, Ling Miao, Ziyu Wang, Jing Shi

Abstract: Graph neural networks (GNNs) are designed to extract latent patterns from graph-structured data, making them particularly well suited for crystal representation learning. Here, we propose a GNN model tailored for estimating electronic transport coefficients in inorganic thermoelectric crystals. The model encodes crystal structures and physicochemical properties in a multiscale manner, encompassing… ▽ More Graph neural networks (GNNs) are designed to extract latent patterns from graph-structured data, making them particularly well suited for crystal representation learning. Here, we propose a GNN model tailored for estimating electronic transport coefficients in inorganic thermoelectric crystals. The model encodes crystal structures and physicochemical properties in a multiscale manner, encompassing global, atomic, bond, and angular levels. It achieves state-of-the-art performance on benchmark datasets with remarkable extrapolative capability. By combining the proposed GNN with \textit{ab initio} calculations, we successfully identify compounds exhibiting outstanding electronic transport properties and further perform interpretability analyses from both global and atomic perspectives, tracing the origins of their distinct transport behaviors. Interestingly, the decision process of the model naturally reveals underlying physical patterns, offering new insights into computer-assisted materials design. △ Less

Submitted 5 June, 2026; v1 submitted 7 December, 2025; originally announced December 2025.

Floquet Superheating

Authors: Yang Hou, Andrea Pizzi, Huike Jin, Johannes Knolle, Roderich Moessner, Hongzheng Zhao

Abstract: Periodically driven many-body systems generally heat towards a featureless 'infinite-temperature' state. As an alternative to uniform heating in a clean system, here we establish a Floquet superheating regime, where fast heating nucleates at ''hot spots" generated by rare fluctuations in the local energy with respect to an appropriate effective Hamiltonian. Striking macroscopic consequences includ… ▽ More Periodically driven many-body systems generally heat towards a featureless 'infinite-temperature' state. As an alternative to uniform heating in a clean system, here we establish a Floquet superheating regime, where fast heating nucleates at ''hot spots" generated by rare fluctuations in the local energy with respect to an appropriate effective Hamiltonian. Striking macroscopic consequences include exceptionally long-lived prethermalization and non-ergodic bimodal distributions of macroscopic observables. Superheating is predicated on a heating rate depending strongly on the local fluctuation; in our example, this is supplied by a sharp state-selective spin-echo, where the energy absorption is strongly suppressed for low-energy states, while thermal fluctuations open up excessive heating channels. A simple phenomenological theory is developed to show the existence of a critical droplet size, which incorporates heating by the driving field as well as the heat current out of the droplet. Our results shine light on a new heating mechanism and suggest new routes towards stabilizing non-equilibrium phases of matter in driven systems. △ Less

Submitted 16 November, 2025; originally announced November 2025.

Signatures of a high-temperature collective electronic phase with superconductivity-like characteristics and a giant pressure effect in networks of boron-doped ultrathin carbon nanotubes

Authors: Y. Wang, T. H. Koo, R. Huang, Y. H. Ng, T. T. Lortz, T. Zhang, W. M. Chan, Y. Hou, J. Pan, S. Krämer, A. Demuer, R. Lortz, N. Wang, P. Sheng

Abstract: We present data consistent with a high-temperature collective electronic phase with superconductivity-like characteristics in three dimensional networks of boron doped, ultrathin carbon nanotubes (CNTs) grown inside the 5 Angstrom channels of ZSM-5 zeolite. Confinement stabilizes (2,1) CNTs that are otherwise dynamically unstable, while boron doping shifts the Fermi level towards a van Hove singul… ▽ More We present data consistent with a high-temperature collective electronic phase with superconductivity-like characteristics in three dimensional networks of boron doped, ultrathin carbon nanotubes (CNTs) grown inside the 5 Angstrom channels of ZSM-5 zeolite. Confinement stabilizes (2,1) CNTs that are otherwise dynamically unstable, while boron doping shifts the Fermi level towards a van Hove singularity, as supported by ab-initio calculations. The resulting CNT network exhibits multiple, mutually consistent signatures of an electronic condensate with the typical characteristics of a high temperature superconductor at ambient pressure. DC magnetization and AC susceptibility measurements reveal the onset of a Meissner response between 220 and 250K, with compacted samples achieving up to 93 percent of full diamagnetic screening. Electrical transport shows a sharp resistive transition with extrapolated Tc = 239K and vanishing resistance in optimized samples. Specific heat measurements display a reproducible anomaly at 233 to 236 K that broadens under magnetic field, consistent with strong fluctuations. Point contact spectroscopy identifies three energy gaps, including a leading gap of 30 meV whose temperature dependence follows BCS expectations for Tc = 224K, and exhibits particle-hole symmetry and Andreev reflection. Remarkably, applying pressures below 0.1 kbar enhances Tc by nearly 100K and modulates the room temperature resistance by more than three orders of magnitude, suggesting a pressure driven 1D to 3D crossover in the CNT network. These results identify boron doped ultrathin CNT networks as a promising carbon-based platform for near ambient temperature superconductivity and reveal an unusually large pressure sensitivity with potential technological relevance. △ Less

Submitted 21 June, 2026; v1 submitted 23 September, 2025; originally announced September 2025.

Highly tunable Gilbert damping in two-dimensional van der Waals ferromagnet Fe3GaTe2: From bilayer to the twisted bilayer

Authors: Jie Wang, Shi-Bo Zhao, Jia-wan Li, Lin Zhuang, Yusheng Hou

Abstract: Van der Waals ferromagnet Fe3GaTe2 possesses both a high Curie temperature and robust perpendicular magnetic anisotropy, holding promise for practical spintronic applications. In particular, understanding and engineering its Gilbert damping which determines magnetization dynamics are crucial for its applications. Here, we investigate the Gilbert damping of bilayer and the twisted bilayer Fe3GaTe2… ▽ More Van der Waals ferromagnet Fe3GaTe2 possesses both a high Curie temperature and robust perpendicular magnetic anisotropy, holding promise for practical spintronic applications. In particular, understanding and engineering its Gilbert damping which determines magnetization dynamics are crucial for its applications. Here, we investigate the Gilbert damping of bilayer and the twisted bilayer Fe3GaTe2 through first-principles calculations. For the bilayer Fe3GaTe2, we obtain a quite low Gilbert damping when its magnetization is along the z axis at room temperature. In addition, the bilayer Fe3GaTe2 exhibits a large orientational anisotropy of Gilbert damping when its magnetization is rotated from the magnetic easy axis to the hard one. Such anisotropy is attributed to the distinct band structures caused by the anisotropic spin-orbit coupling. Surprisingly, we find that twisting the bilayer Fe3GaTe2 can effectively reduce the Gilbert damping for the perpendicular magnetization, and enhance the orientational anisotropy of Gilbert damping up to 635% when rotating the magnetization from the magnetic easy axis to the hard one. These findings open up an entirely new avenue for the manipulation of Gilbert damping and its anisotropy in two-dimensional van der Waals ferromagnets. △ Less

Submitted 9 September, 2025; originally announced September 2025.

Comments: 5 Figures, accepted by Physical Review B

Giant Anomalous Hall Conductivity and Gilbert Damping in Room-temperature Ferromagnetic Half-Heusler Alloys PtMnBi

Authors: Hong-Xue Jiang, Jia-wan Li, Shi-Bo Zhao, Jie Wang, Yusheng Hou

Abstract: Half-Heusler alloys have emerged as promising candidates for novel spintronic applications due to their exceptional properties including the high Curie temperature (TC) above room temperature and large anomalous Hall conductivity (AHC). In this work, we systematically study the magnetic and electronic properties of PtMnBi in α-, \{beta}-, and γ-phase using first-principles calculations and Monte C… ▽ More Half-Heusler alloys have emerged as promising candidates for novel spintronic applications due to their exceptional properties including the high Curie temperature (TC) above room temperature and large anomalous Hall conductivity (AHC). In this work, we systematically study the magnetic and electronic properties of PtMnBi in α-, \{beta}-, and γ-phase using first-principles calculations and Monte Carlo simulations. The three phases are found to be ferromagnetic metals. In particular, the α-phase PtMnBi shows a high TC up to 802 K and a relatively large Gilbert damping of 0.085. Additionally, the γ-phase PtMnBi possesses a non-negligible AHC, reaching 203 Ω-1cm-1 at the Fermi level. To evaluate its potential in nanoscale devices, we further investigate the α-phase PtMnBi thin films. The Gilbert dampings of α-phase PtMnBi thin films varies with film thickness and we attribute this variation to the distinct band structures at the high-symmetry point Γ, which arise from differences in film thickness. Moreover, the 1-layer (1L) α-phase thin film retains robust ferromagnetism (TC = 688 K) and shows enhanced Gilbert damping (0.14) and AHC (1116 Ω-1cm-1) compared to the bulk. Intriguingly, under a 2% in-plane biaxial compressive strain, the Gilbert damping of 1L α-phase PtMnBi thin film increases to 0.17 and the AHC reaches 2386 Ω-1cm-1. The coexistence of giant Gilbert damping and large AHC makes α-phase PtMnBi a compelling platform for practical spintronic applications, and highlights the potential of half-Heusler alloys in spintronic device design. △ Less

Submitted 26 August, 2025; originally announced August 2025.

Comments: 16 pages, 5 figures, accepted by Frontiers of Physics

Magnetic Anisotropy in Two-dimensional van der Waals Magnetic Materials and Their Heterostructures: Importance, Mechanisms, and Opportunities

Authors: Yusheng Hou, Ruqian Wu

Abstract: Two-dimensional (2D) magnetism in atomically thin van der Waals (vdW) monolayers and heterostructures has attracted significant attention due to its promising potential for next-generation spintronic and quantum technologies. A key factor in stabilizing long-range magnetic order in these systems is magnetic anisotropy, which plays a crucial role in overcoming the limitations imposed by the Mermin-… ▽ More Two-dimensional (2D) magnetism in atomically thin van der Waals (vdW) monolayers and heterostructures has attracted significant attention due to its promising potential for next-generation spintronic and quantum technologies. A key factor in stabilizing long-range magnetic order in these systems is magnetic anisotropy, which plays a crucial role in overcoming the limitations imposed by the Mermin-Wagner theorem. This review provides a comprehensive theoretical and experimental overview of the importance of magnetic anisotropy in enabling intrinsic 2D magnetism and shaping the electronic, magnetic, and topological properties of 2D vdW materials. We begin by summarizing the fundamental mechanisms that determine magnetic anisotropy, emphasizing the contributions from strong ligand spin-orbit coupling of ligand atoms and unquenched orbital magnetic moments. We then examine a range of material engineering approaches, including alloying, doping, electrostatic gating, strain, and pressure, that have been employed to effectively tune magnetic anisotropy in these materials. Finally, we discuss open challenges and promising future directions in this rapidly advancing field. By presenting a broad perspective on the role of magnetic anisotropy in 2D magnetism, this review aims to stimulate ongoing efforts and new ideas toward the realization of robust, room-temperature applications based on 2D vdW magnetic materials and their heterostructures. △ Less

Submitted 6 August, 2025; originally announced August 2025.

Comments: A topic review of magnetic anisotropy of 2D magnetic materials

Journal ref: Advanced Functional Materials (2025)

Anomalous magnetoresistance in an antiferromagnetic Kagome semimetal heterostructures

Authors: Xionghua Liu, Qiyuan Feng, Weibin Cui, Hanjie Guo, Yubin Hou, Xiaomin Zhang, Yongcheng Deng, Dong Zhang, Jing Zhang, Qingyou Lu, Kaiyou Wang

Abstract: Antiferromagnetic Kagome semimetals have attracted tremendous attentions for their potential application in antiferromagnetic topological spintronics. Effectively manipulating Kagome antiferromagnetic states could reveal abundant physical phenomena induced from quantum interactions between topology, spin, and correlation. Here, we achieved tunable spin textures of FeSn thin films via introducing i… ▽ More Antiferromagnetic Kagome semimetals have attracted tremendous attentions for their potential application in antiferromagnetic topological spintronics. Effectively manipulating Kagome antiferromagnetic states could reveal abundant physical phenomena induced from quantum interactions between topology, spin, and correlation. Here, we achieved tunable spin textures of FeSn thin films via introducing interfacial Dzyaloshinskii Moriya interaction from heavy-metal Pt overlayer. With increasing FeSn thickness, the variable spin textures result in gradual change in Hall resistivity and magnetoresistance. Importantly, an unconventional damped oscillatory-like behavior of magnetoresistance at relatively low magnetic field can be observed in thin FeSn-Pt samples. This oscillatory like magnetoresistance feature was confirmed to be related to the special topological spin textures revealed by magnetic force microscopy measurements. The formation of rich variety of topological spin textures in association with exotic magneto-transport properties in antiferromagnetic Kagome FeSn heterostructures offers new perspectives for understanding the novel emergent phenomena in Kagome antiferromagnets. △ Less

Submitted 23 July, 2025; originally announced July 2025.

Comments: 15 pages, 4 figures

Unconventional Superconductivity in $\mathrm{La_{3}Ni_{2}O_{7}}$ from the Perspective of Symmetry

Authors: Guan-Hao Feng, Jun Quan, Yusheng Hou

Abstract: The recently discovered superconductor $\mathrm{La_{3}Ni_{2}O_{7}}$ has attracted significant attention due to its remarkably high transition temperature ($T_{c}$) under high pressure. Shortly after this discovery, thin-film $\mathrm{La_{3}Ni_{2}O_{7}}$ was demonstrated to exhibit ambient-pressure superconductivity; however, the corresponding $T_c$ is only about half that of the pressurized bulk m… ▽ More The recently discovered superconductor $\mathrm{La_{3}Ni_{2}O_{7}}$ has attracted significant attention due to its remarkably high transition temperature ($T_{c}$) under high pressure. Shortly after this discovery, thin-film $\mathrm{La_{3}Ni_{2}O_{7}}$ was demonstrated to exhibit ambient-pressure superconductivity; however, the corresponding $T_c$ is only about half that of the pressurized bulk material. This striking difference raises questions about the underlying mechanisms governing superconductivity in these two structures. To address this issue, we develop a phenomenological symmetry-based method to investigate the superconducting gap structure in $\mathrm{La_{3}Ni_{2}O_{7}}$. Using density-functional theory methods (DFT+$U$), together with the experimentally determined $T_c$ and structural symmetry, we find that both pressurized bulk and thin-film $\mathrm{La_{3}Ni_{2}O_{7}}$ exhibit $s_{\pm}$-wave pairing symmetry and two-gap superconductivity, yet their dominant microscopic pairing configurations are distinct. In the pressurized bulk, superconductivity is dominated by the out-of-plane pairing of the Ni-$d_{z^2}$ orbitals, while in the thin film, the in-plane pairing of the Ni-$d_{x^2-y^2}$ orbitals prevails. Furthermore, the observed reduction in $T_c$ can be attributed to this transition of the dominant pairing type, driven by the decreased ratio of inter-layer to intra-layer hoppings in the thin film. Our result sheds lights on the microscopic pairing in $\mathrm{La_{3}Ni_{2}O_{7}}$ and reveals the significance of the symmetry. This method can potentially be generalized to a broader range of unconventional superconductors. △ Less

Submitted 4 May, 2026; v1 submitted 2 June, 2025; originally announced June 2025.

Ambient-pressure superconductivity onset at 10 K and robust Tc under high pressure in TiNbTaN3 medium-entropy nitride

Authors: Lingyong Zeng, Jie Wang, Hongyu Liu, Longfu Li, Jinjun Qin, Yucheng Li, Rui Chen, Jing Song, Yusheng Hou, Huixia Luo

Abstract: Superconductivity has been one of the focal points in medium and high-entropy alloys (MEAs-HEAs) since the first discovery of the HEA superconductor in 2014. Until now, most HEAs' superconducting transition temperature (Tc) has not exceeded 10 K. Here we report the first observation of superconductivity in a bulk medium-entropy nitride (MEN), TiNbTaN3, which shows a Tc of 10 K at ambient pressure.… ▽ More Superconductivity has been one of the focal points in medium and high-entropy alloys (MEAs-HEAs) since the first discovery of the HEA superconductor in 2014. Until now, most HEAs' superconducting transition temperature (Tc) has not exceeded 10 K. Here we report the first observation of superconductivity in a bulk medium-entropy nitride (MEN), TiNbTaN3, which shows a Tc of 10 K at ambient pressure. Notably, the electronic specific heat coefficient γ(H) exhibits nonlinear H-dependence behavior, which is similar to other well-studied multigap superconductors. Furthermore, TiNbTaN3 exhibits extraordinary pressure resilience, maintaining robust superconductivity under high-pressure conditions. Density functional theory (DFT) calculations indicate that pressure exerts a negligible impact on the electronic structures of TiNbTaN3, thereby corroborating the experimental observations. These findings not only advance our understanding of emergent phenomena in entropy-stabilized nitrides but also establish a new material platform for finding more high-Tc superconductors with combinations of 4d/5d transition metal elements and light elements, motivating further investigations into high-entropy functional ceramics for extreme environment applications. △ Less

Submitted 21 May, 2025; originally announced May 2025.

Comments: 21 pages, 7 figures. The manuscript with the same title will be published by Advanced Science

Journal ref: Advanced Science 2025

Reconfigurable Room Temperature Exchange Bias through Néel Order Switching in van der Waals Heterostructures

Authors: Jicheng Wang, Shilei Ding, Bei Ding, Zhipeng Hou, Licong Peng, Yilan Jiang, Fengshan Zheng, Zhaochu Luo, Yu Ye, Jinbo Yang, Yanglong Hou, Rui Wu

Abstract: Exchange bias effect plays a crucial role in modern magnetic memory technology. Recently, van der Waals magnetic materials have emerged and shown potential in spintronic devices at atomic scale. Owing to their tunable physical properties and the flexibility in fabrication, the van der Waals heterostructures offer more possibilities for investigating potential mechanisms of the exchange bias effect… ▽ More Exchange bias effect plays a crucial role in modern magnetic memory technology. Recently, van der Waals magnetic materials have emerged and shown potential in spintronic devices at atomic scale. Owing to their tunable physical properties and the flexibility in fabrication, the van der Waals heterostructures offer more possibilities for investigating potential mechanisms of the exchange bias effect. However, due to low magnetic ordering temperatures for most van der Waals magnets, to establish exchange bias in van der Waals antiferromagnet/ferromagnet heterostructures at room temperature is challenging. In this study, we fabricate (Fe$_{0.56}$Co$_{0.44}$)$_{5}$GeTe$_{2}$(FCGT)/Fe$_{3}$GaTe$_{2}$(FGaT) heterostructures with magnetic ordering temperatures of each component well above room temperature to achieve a room temperature exchange bias effect. It is found that the sign and magnitude of the exchange bias field can be efficiently controlled by manipulating the Néel order of FCGT with magnetic field. The manipulation of Néel order shows significant magnetic field dependence. A strong pre-set field induces a switch in the Néel order of FCGT, which aligns the interfacial magnetization at the FCGT/FGaT interface, leading to robust exchange bias, as revealed by both transport measurements and macro-spin model calculations. Our findings demonstrate the intrinsic manipulation and switchable of room-temperature exchange bias in all-van der Waals heterostructures and further promote the development of novel two-dimensional spintronic devices. △ Less

Submitted 7 May, 2025; originally announced May 2025.

Comments: 24 pages, 4 figures

Accelerating Multi-Objective Collaborative Optimization of Doped Thermoelectric Materials via Artificial Intelligence

Authors: Yuxuan Zeng, Wenhao Xie, Wei Cao, Tan Peng, Yue Hou, Ziyu Wang, Jing Shi

Abstract: The thermoelectric performance of materials exhibits complex nonlinear dependencies on both elemental types and their proportions, rendering traditional trial-and-error approaches inefficient and time-consuming for material discovery. In this work, we present a deep learning model capable of accurately predicting thermoelectric properties of doped materials directly from their chemical formulas, a… ▽ More The thermoelectric performance of materials exhibits complex nonlinear dependencies on both elemental types and their proportions, rendering traditional trial-and-error approaches inefficient and time-consuming for material discovery. In this work, we present a deep learning model capable of accurately predicting thermoelectric properties of doped materials directly from their chemical formulas, achieving state-of-the-art performance. To enhance interpretability, we further incorporate sensitivity analysis techniques to elucidate how physical descriptors affect the thermoelectric figure of merit (zT). Moreover, we establish a coupled framework that integrates a surrogate model with a multi-objective genetic algorithm to efficiently explore the vast compositional space for high-performance candidates. Experimental validation confirms the discovery of a novel thermoelectric material with superior $zT$ values in the medium-temperature regime. △ Less

Submitted 11 April, 2025; originally announced April 2025.

Layer-dependent field-free switching of Néel vector in a van der Waals antiferromagnet

Authors: Haoran Guo, Zhongchong Lin, Jinhao Lu, Chao Yun, Guanghui Han, Shoutong Sun, Yu Wu, Wenyun Yang, Dongdong Xiao, Zhifeng Zhu, Licong Peng, Yu Ye, Yanglong Hou, Jinbo Yang, Zhaochu Luo

Abstract: Two-dimensional antiferromagnets, combining the dual advantages of van der Waals (vdW) and antiferromagnetic materials, provide an unprecedented platform for exploring emergent spin-related phenomena. However, electrical manipulation of Néel vectors in vdW antiferromagnets - the cornerstone of antiferromagnetic spintronics - remains challenging. Here, we report layer-dependent electrical switching… ▽ More Two-dimensional antiferromagnets, combining the dual advantages of van der Waals (vdW) and antiferromagnetic materials, provide an unprecedented platform for exploring emergent spin-related phenomena. However, electrical manipulation of Néel vectors in vdW antiferromagnets - the cornerstone of antiferromagnetic spintronics - remains challenging. Here, we report layer-dependent electrical switching of the Néel vector in an A-type vdW antiferromagnet $(Fe,Co)_3$$GaTe_2$ (FCGT) with perpendicular magnetic anisotropy. The Néel vector of FCGT with odd-number vdW layers can be 180° reversed via spin-orbit torques. Furthermore, we achieve field-free switching in an all-vdW, all-antiferromagnet heterostructure of FCGT/CrSBr in which the noncollinear interfacial spin texture breaks the mirror symmetry. Our results establish layer-controlled spin symmetries and interfacial spin engineering as universal paradigms for manipulating antiferromagnetic order, paving the way for realising reliable and efficient vdW antiferromagnetic devices. △ Less

Submitted 9 April, 2025; originally announced April 2025.

Giant Self Spin-Valve Effect in the Kagome Helimagnet

Authors: Xitong Xu, Yonglai Liu, Kesen Zhao, Che-Min Lin, Miao He, Haitian Zhao, Qingqi Zeng, Yubin Hou, Qingyou Lu, Ding-Fu Shao, Shuang Jia, Haifeng Du, Wenjie Meng, Tay-Rong Chang, Zhe Qu

Abstract: Kagome magnets can combine non-trivial band topology and electron correlations, offering a versatile playground for various quantum phenomena. In this work we propose that kagome magnets with frustrated interlayer interactions can intrinsically support a self spin-valve effect, and experimentally confirm this in the kagome helimagnet TmMn$_6$Sn$_6$. Under a magnetic field perpendicular to the heli… ▽ More Kagome magnets can combine non-trivial band topology and electron correlations, offering a versatile playground for various quantum phenomena. In this work we propose that kagome magnets with frustrated interlayer interactions can intrinsically support a self spin-valve effect, and experimentally confirm this in the kagome helimagnet TmMn$_6$Sn$_6$. Under a magnetic field perpendicular to the helical axis, using magnetic force microscopy we observed stripe domains that stack strictly along the helical axis, which we attribute to the stability loss of the kagome helimagnetic state. Such a domain pattern spontaneously mimics the artificial multilayered structure in traditional spin valves, which, combined with the high spin polarization, leads to a giant magnetoresistance (GMR) ratio over 160%. This discovery opens an avenue to realize inherent spin valves in a variety of quantum magnets, and can hold promise in future spintronics. △ Less

Submitted 20 March, 2025; originally announced March 2025.

Comments: Accepted version

Journal ref: Nat. Commun. 16, 2630 (2025)

Colossal magnetoresistance in a quasi-two-dimensional cluster glass semiconductor

Authors: Suman Kalyan Pradhan, Weiqi Liu, Jicheng Wang, Yongli Yu, Wenxing Chen, Jinbo Yang, Yanglong Hou, Rui Wu

Abstract: With a surge of interest in spintronics, the manipulation and detection of colossal magnetoresistance in quasi-two-dimensional layered magnetic materials have become a key focus, driven by their relatively scarce occurrence compared to giant magnetoresistance and tunneling magnetoresistance. This study presents an investigation into the desired colossal magnetoresistance, achieved by introducing m… ▽ More With a surge of interest in spintronics, the manipulation and detection of colossal magnetoresistance in quasi-two-dimensional layered magnetic materials have become a key focus, driven by their relatively scarce occurrence compared to giant magnetoresistance and tunneling magnetoresistance. This study presents an investigation into the desired colossal magnetoresistance, achieved by introducing magnetic frustration through Te doping in quasi-two-dimensional antiferromagnet Cr2Se3 matrix. The resulting Cr0.98SeTe0.27 exhibits cluster glass-like behavior with a freezing temperature of 28 K. Magnetotransport studies reveal a significant negative magnetoresistance of up to 32%. Additionally, angle-dependent transport measurements demonstrate a magnetic field-induced transition from positive to negative resistance anisotropy, suggesting a magnetic field-driven alteration in the electronic structure of this narrow band gap semiconductor, a characteristic feature of the colossal magnetoresistance effect. This behavior is further corroborated by density functional theory calculations. This systematic investigation provides a crucial understanding of the control of colossal magnetoresistance in quasi-two-dimensional materials via competing exchange interactions. △ Less

Submitted 25 February, 2025; originally announced February 2025.

A Versatile Three Dimensional Traction Force Microscopy Framework for Uncovering the Mechanics of Bio-Adhesion

Authors: Yingwei Hou, Fusheng Wang, Tao Liu

Abstract: This study presents a novel, versatile traction force microscopy framework for quantifying three-dimensional (3D) interfacial forces during bio-adhesion by integrating in situ stereo digital image correlation with finite element (FE) simulation. The method enables accurate measurement of microscale displacements and force distributions at the interfaces in both dry and wet environments, addressing… ▽ More This study presents a novel, versatile traction force microscopy framework for quantifying three-dimensional (3D) interfacial forces during bio-adhesion by integrating in situ stereo digital image correlation with finite element (FE) simulation. The method enables accurate measurement of microscale displacements and force distributions at the interfaces in both dry and wet environments, addressing limitations of conventional microscopy techniques related to limited measurement scales, restricted fields of view, and surface disturbance from contact or fluorescence. An analytical model was developed to guide the design of a deformable substrate, supporting selection of substrate material and thickness of the substrate. System accuracy was examined through steel ball compression experiments, which were validated against FE simulations. The framework was applied to marine mussel plaque adhesion under 15 directional tension to characterize interfacial traction force distributions. Sensitivity analyses examined the effects of Poisson's ratio, Young's modulus, and constitutive models on the results. This approach offers a versatile platform for investigating interfacial mechanics in adhesives, with broad relevance to bioengineering applications. △ Less

Submitted 8 January, 2026; v1 submitted 17 February, 2025; originally announced February 2025.

Journal ref: Advanced Science, December 2025

Strong and Tunable Electrical-Anisotropy in Type-II Weyl Semimetal Candidate WP2 with Broken Inversion Symmetry

Authors: Bo Su, Yanpeng Song, Yanhui Hou, Xu Chen, Jianzhou Zhao, Yongchang Ma, Yang Yang, Jiangang Guo, Jianlin Luo, Zhi-Guo Chen

Abstract: A transition metal diphosphide WP2 is a candidate for type-II Weyl semimetals (WSMs) in which spatial inversion symmetry is broken and Lorentz invariance is violated. As one of the key prerequisites for the presence of the WSM state in WP2, spatial inversion symmetry breaking in this compound has rarely been investigated by experiments. Furthermore, how much anisotropy the electrical properties of… ▽ More A transition metal diphosphide WP2 is a candidate for type-II Weyl semimetals (WSMs) in which spatial inversion symmetry is broken and Lorentz invariance is violated. As one of the key prerequisites for the presence of the WSM state in WP2, spatial inversion symmetry breaking in this compound has rarely been investigated by experiments. Furthermore, how much anisotropy the electrical properties of WP2 have and whether its electrical anisotropy can be tuned remain elusive. Here, we report angle-resolved polarized Raman spectroscopy, electrical transport, optical spectroscopy and first-principle studies of WP2. The energies of the observed Raman-active phonons and the angle dependences of the phonon intensities are well consistent with the results obtained by first-principle calculations and the analysis of the proposed crystal symmetry without spatial inversion, providing evidence that spatial inversion symmetry is broken in WP2. Moreover, the measured ratio (Rc/Ra) between the crystalline c-axis and a-axis electrical resistivities exhibits a weak dependence on temperature from 100 to 250 K, but increases abruptly below 100 K, and then reaches the value of 8.0 at 10 K, which is by far the strongest in-plane electrical resistivity anisotropy among the reported type-II WSM candidates with comparable carrier concentrations. Our optical-spectroscopy and calculation studies reveal that the abrupt enhancement of the Rc/Ra below 100 K mainly arises from a sharp increase in the scattering rate anisotropy at low temperatures. More interestingly, the Rc/Ra at 10 K can be tuned from 8.0 to 10.6 as the magnetic field increases from 0 to 9 T. The stronge and tunable electrical resistivity anisotropy found in WP2 can serve as a degree of freedom for tuning the electrical properties of type-II WSMs, which paves the way for developing novel electronic applications based on type-II WSMs. △ Less

Submitted 12 February, 2025; originally announced February 2025.

Comments: Published in Advanced Materials

Journal ref: Advanced Materials 31, 1903498 (2019)

Nonmagnetic ground state of marcasite FeTe$_{2}$: The competition between crystal field splitting and on-site Coulomb repulsion

Authors: Yue-Fei Hou, Zhibin Shao, Minghu Pan, Shiyang Wu, Fawei Zheng, Zhen-Guo Fu, Ping Zhang

Abstract: The magnetic ground states in crystalline systems are significant for both fundamental condensed matter physics and practical materials engineering. Marcasite FeTe$_{2}$, characterized as a small-gap semiconductor, exhibits anomalous magnetic behaviors in low-temperature experiments. In this study, first-principles density functional theory calculations combined with scanning tunneling microscopy/… ▽ More The magnetic ground states in crystalline systems are significant for both fundamental condensed matter physics and practical materials engineering. Marcasite FeTe$_{2}$, characterized as a small-gap semiconductor, exhibits anomalous magnetic behaviors in low-temperature experiments. In this study, first-principles density functional theory calculations combined with scanning tunneling microscopy/spectroscopy are employed to investigate the magnetic ground state of marcasite FeTe$_{2}$. It is revealed that the competition between crystal field splitting and on-site Coulomb repulsion plays the key role in the formation of localized magnetic moments in FeTe$_{2}$. The ground state of FeTe$_{2}$ bulk is confirmed to be nonmagnetic, while the magnetic responses of FeTe$_{2}$ observed at low temperature are suggested to be related to the magnetic Fe atoms on the crystal surfaces. Our work proposes a straightforward competing mechanism for determining ground-state magnetism of various localized-moment crystalline systems. △ Less

Submitted 17 June, 2025; v1 submitted 7 February, 2025; originally announced February 2025.

Comments: 5 figures, 10 pages. Some revisions were performed. Comments are welcome

First-principles study of electronic and magnetic properties of self-intercalated van der Waals magnet Cr$_3$Ge$_2$Te$_6$

Authors: Jia-wan Li, Shi-Bo Zhao, Lin Zhuang, Yusheng Hou

Abstract: Self-intercalated van der Waals magnets, characterized by self-intercalating native atoms into van der Waals layered structures with intrinsic magnetism, exhibit a variety of novel physical properties. Here, using first-principles calculations and Monte Carlo simulations, we report a self-intercalated van der Waals ferromagnet, Cr$_3$Ge$_2$Te$_6$, which has a high Curie temperature of 492 K. We fi… ▽ More Self-intercalated van der Waals magnets, characterized by self-intercalating native atoms into van der Waals layered structures with intrinsic magnetism, exhibit a variety of novel physical properties. Here, using first-principles calculations and Monte Carlo simulations, we report a self-intercalated van der Waals ferromagnet, Cr$_3$Ge$_2$Te$_6$, which has a high Curie temperature of 492 K. We find that Cr$_3$Ge$_2$Te$_6$ is nearly half-metallic with a spin polarization reaching up to 90.9%. Due to the ferromagnetism and strong spin-orbit coupling effect in Cr$_3$Ge$_2$Te$_6$, a large anomalous Hall conductivity of 138 $Ω^{-1}$ cm$^{-1}$ and 305 $Ω^{-1}$ cm$^{-1}$ can be realized when its magnetization is along its magnetic easy axis and hard axis, respectively. By doping electrons (holes) into Cr$_3$Ge$_2$Te$_6$, these anomalous Hall conductivities can be increased up to 318 $Ω^{-1}$ cm$^{-1}$ (648 $Ω^{-1}$ cm$^{-1}$). Interestingly, a 5-layer Cr$_3$Ge$_2$Te$_6$ thin film retains the room-temperature ferromagnetism with a higher spin polarization and larger anomalous Hall conductivity. Our work demonstrates that Cr$_3$Ge$_2$Te$_6$ is a novel room-temperature self-intercalated ferromagnet with high spin polarization and large anomalous Hall conductivity, offering great opportunities for designing nano-scale electronic devices. △ Less

Submitted 17 January, 2025; originally announced January 2025.

Comments: 16 pages, 6 figures, accepted by Chinese Physics B

Non-Hermitian quasicrystalline topological insulators

Authors: Xiaolu Zhu, Tan Peng, Fang Lyu, Wei Cao, Yue Hou, Rui Xiong, Ziyu Wang

Abstract: In recent years, the interplay between non-Hermiticity and band topology is expected to uncover numerous novel physical phenomena. However, the majority of research has focused on periodic crystalline structures, with comparatively fewer studies exploring quasicrystalline systems. In this paper, we delve into the influence of asymmetric hopping on the topological insulators, specifically focusing… ▽ More In recent years, the interplay between non-Hermiticity and band topology is expected to uncover numerous novel physical phenomena. However, the majority of research has focused on periodic crystalline structures, with comparatively fewer studies exploring quasicrystalline systems. In this paper, we delve into the influence of asymmetric hopping on the topological insulators, specifically focusing on quantum spin Hall insulators and higher-order topological insulators in an octagonal Ammann-Beenker quasicrystalline lattice. We demonstrate that asymmetric hopping can significantly alter the distribution of edge states, leading to a uniform distribution across all boundaries or localizing them at a single edge, depending on the symmetry adjustments. Furthermore, we explore the robustness of higher-order topological corner states under perturbations, showing that these states can maintain their distribution even in the presence of non-Hermiticity. Our findings not only expand the current understanding of topological states in quasicrystals under non-Hermitian conditions, but also provide valuable theoretical guidance for manipulating corner state distributions in non-Hermitian quasicrystalline higher-order topological insulators. △ Less

Submitted 21 December, 2024; originally announced December 2024.

Comments: 10 pages,10 figures

Accelerating the Discovery of Materials with Expected Thermal Conductivity via a Synergistic Strategy of DFT and Interpretable Deep Learning

Authors: Yuxuan Zeng, Wei Cao, Yijing Zuo, Tan Peng, Yue Hou, Ling Miao, Ziyu Wang, Jing Shi

Abstract: Lattice thermal conductivity (LTC) is a critical parameter for thermal transport properties, playing a pivotal role in advancing thermoelectric materials and thermal management technologies. Traditional computational methods, such as Density Functional Theory (DFT) and Molecular Dynamics (MD), are resource-intensive, limiting their applicability for high-throughput LTC prediction. While AI-driven… ▽ More Lattice thermal conductivity (LTC) is a critical parameter for thermal transport properties, playing a pivotal role in advancing thermoelectric materials and thermal management technologies. Traditional computational methods, such as Density Functional Theory (DFT) and Molecular Dynamics (MD), are resource-intensive, limiting their applicability for high-throughput LTC prediction. While AI-driven approaches have made significant strides in material science, the trade-off between accuracy and interpretability remains a major bottleneck. In this study, we introduce an interpretable deep learning framework that enables rapid and accurate LTC prediction, effectively bridging the gap between interpretability and precision. Leveraging this framework, we identify and validate four promising thermal conductors/insulators using DFT and MD. Moreover, by combining sensitivity analysis with DFT calculations, we uncover novel insights into phonon thermal transport mechanisms, providing a deeper understanding of the underlying physics. This work not only accelerates the discovery of thermal materials but also sets a new benchmark for interpretable AI in material science. △ Less

Submitted 19 September, 2025; v1 submitted 8 December, 2024; originally announced December 2024.

Simultaneous Topology Optimization of Differentiable and Non-Differentiable Objectives via Morphology Learning: Stiffness and Cell Growth on Scaffold

Authors: Weiming Wang, Yanhao Hou, Renbo Su, Weiguang Wang, Charlie C. L. Wang

Abstract: Topology optimization of microstructures plays a critical role in optimizing functional performance across diverse engineering applications. While metamaterials with enhanced mechanical properties -- such as hyperelasticity, energy absorption, and thermal efficiency -- are commonly designed using complex microstructural geometries and multi-physics simulations, achieving the simultaneous optimizat… ▽ More Topology optimization of microstructures plays a critical role in optimizing functional performance across diverse engineering applications. While metamaterials with enhanced mechanical properties -- such as hyperelasticity, energy absorption, and thermal efficiency -- are commonly designed using complex microstructural geometries and multi-physics simulations, achieving the simultaneous optimization of mechanical performance and non-differentiable objectives remains a significant challenge. In this work, we propose a novel framework for simultaneous topology optimization of differentiable and non-differentiable objectives via a data-driven morphology learning approach. The framework extracts shape patterns from a curated dataset of microstructures recognized for their superior performance in specific functional applications. To showcase the versatility of the approach, we apply it to the optimization of scaffolds for bone tissue engineering, with cell growth as a representative functional objective. By integrating learned morphology patterns into a topology optimization process, the method generates microstructures that effectively balance mechanical stiffness and biological performance, such as enhanced cell proliferation. As a case study, we demonstrate a scaffold design that improves mechanical stiffness by 29.69% and cell growth by 37.05% on Day 7 and 33.30% on Day 14. This approach highlights the general applicability of the proposed framework for optimizing a broad range of engineering challenges, beyond the specific case of cell growth. △ Less

Submitted 24 January, 2025; v1 submitted 15 October, 2024; originally announced October 2024.

Wave function forms of interlayer excitons in bilayer transition metal dichalcogenides

Authors: Jianju Tang, Songlei Wang, Yuhang Hou, Hongyi Yu

Abstract: We numerically solve the electron-hole relative wave function of interlayer excitons in bilayer transition metal dichalcogenides, taking into account the screening effects from both the constituent transition metal dichalcogenides layers and the surrounding dielectric environment. We find that the wave function of the 1s ground state is close to the gaussian form, rather than the well-known expone… ▽ More We numerically solve the electron-hole relative wave function of interlayer excitons in bilayer transition metal dichalcogenides, taking into account the screening effects from both the constituent transition metal dichalcogenides layers and the surrounding dielectric environment. We find that the wave function of the 1s ground state is close to the gaussian form, rather than the well-known exponential decay form of the two-dimensional hydrogen model. Meanwhile, the 2s state has an energy $E_{2s}$ significantly higher than $E_{2p}$ of the 2p state, but becomes close to $E_{3d}$ of the 3d state with $E_{2s}-E_{2p} \approx E_{3d}-E_{2p} \approx E_{2p}-E_{1s}$ under a large interlayer separation and weak environmental screening. Under general conditions, the solved 1s, 2p and 3d wave functions can be fit nearly perfectly by simple analytic forms which smoothly cross from gaussian to exponential decay. These analytic forms can facilitate the accurate evaluation of various exciton quantities for device applications. △ Less

Submitted 22 October, 2024; originally announced October 2024.

Thickness-dependent anisotropic Gilbert damping in heterostructures of ferromagnets and two-dimensional ferroelectric bismuth monolayer

Authors: Shi-Bo Zhao, Xiang-Fan Huang, Ze-quan Wang Ruqian Wu, Yusheng Hou

Abstract: The Gilbert damping parameter, which describes magnetization dynamics, is crucial for the performance of modern spintronic devices, affecting factors such as the switching speed and critical current density of magnetoresistive random access memory. Thus, the ability to engineer it on demand is pivotal for developing novel spintronic applications. In this work, we systematically examine the Gilbert… ▽ More The Gilbert damping parameter, which describes magnetization dynamics, is crucial for the performance of modern spintronic devices, affecting factors such as the switching speed and critical current density of magnetoresistive random access memory. Thus, the ability to engineer it on demand is pivotal for developing novel spintronic applications. In this work, we systematically examine the Gilbert damping parameter of Fe films in contact with a black phosphorus-like bismuth monolayer using first-principles calculations. In these Bi/Fe heterostructures, we obtain a significantly enhanced Gilbert damping owing to strong interfacial spin-orbit couplings (SOCs). Interestingly, we find non-monotonic thickness-dependent Gilbert damping anisotropy and attribute that to the competition between the interfacial SOC and the intrinsically anisotropic SOC of Fe films. We further demonstrate that these SOC effects lead to anisotropic band structures, which are responsible for the anisotropic Gilbert damping. Our work provides a deep understanding of the anisotropic Gilbert damping and opens avenues for exploring it in ferromagnetic heterostructures. △ Less

Submitted 24 September, 2024; originally announced September 2024.

Comments: 22 Pages, 5 Figures, accepted by PRB

Journal ref: Phys. Rev. B 110, 094435 (2024)

Topological Surface State Evolution in Bi$_2$Se$_3$ via Surface Etching

Authors: Ziqin Yue, Jianwei Huang, Ruohan Wang, Jia-Wan Li, Hongtao Rong, Yucheng Guo, Han Wu, Yichen Zhang, Junichiro Kono, Xingjiang Zhou, Yusheng Hou, Ruqian Wu, Ming Yi

Abstract: Topological insulators are materials with an insulating bulk interior while maintaining gapless boundary states against back scattering. Bi$_2$Se$_3$ is a prototypical topological insulator with a Dirac-cone surface state around $Γ$. Here, we present a controlled methodology to gradually remove Se atoms from the surface Se-Bi-Se-Bi-Se quintuple layers, eventually forming bilayer-Bi on top of the q… ▽ More Topological insulators are materials with an insulating bulk interior while maintaining gapless boundary states against back scattering. Bi$_2$Se$_3$ is a prototypical topological insulator with a Dirac-cone surface state around $Γ$. Here, we present a controlled methodology to gradually remove Se atoms from the surface Se-Bi-Se-Bi-Se quintuple layers, eventually forming bilayer-Bi on top of the quintuple bulk. Our method allows us to track the topological surface state and confirm its robustness throughout the surface modification. Importantly, we report a relocation of the topological Dirac cone in both real space and momentum space, as the top surface layer transitions from quintuple Se-Bi-Se-Bi-Se to bilayer-Bi. Additionally, charge transfer among different surface layers is identified. Our study provides a precise method to manipulate surface configurations, allowing for the fine-tuning of the topological surface states in Bi$_2$Se$_3$, which represents a significant advancement towards nano-engineering of topological states. △ Less

Submitted 18 September, 2024; originally announced September 2024.

Comments: 21 pages, 5 figures, accepted for publication in Nano Letters

Floquet-engineered Emergent Massive Nambu-Goldstone Modes

Authors: Yang Hou, Zhanpeng Fu, Roderich Moessner, Marin Bukov, Hongzheng Zhao

Abstract: We present a general framework to implement massive Nambu-Goldstone quasi-particles in driven many-body systems. The underlying mechanism leverages an explicit Lie group structure imprinted into an effective Hamiltonian that governs the dynamics of slow degrees of freedom; the resulting emergent continuous symmetry is weakly explicitly broken, giving rise to a massive Nambu-Goldstone mode, with a… ▽ More We present a general framework to implement massive Nambu-Goldstone quasi-particles in driven many-body systems. The underlying mechanism leverages an explicit Lie group structure imprinted into an effective Hamiltonian that governs the dynamics of slow degrees of freedom; the resulting emergent continuous symmetry is weakly explicitly broken, giving rise to a massive Nambu-Goldstone mode, with a spectral mass gap scaling linearly with the drive period. We discuss explicit and experimentally implementable realizations, such as Heisenberg-like spin models that support gapped spin-wave excitations. We provide a protocol to certify the existence of the massive Nambu-Goldstone mode from the dynamics of specific observables, and analyse the dispersion spectrum and their lifetime in the presence of weak explicit symmetry breaking. △ Less

Submitted 27 July, 2025; v1 submitted 3 September, 2024; originally announced September 2024.

Journal ref: Phys. Rev. B 112, L020305 (2025)

Signatures of a Spin-Active Interface and Locally Enhanced Zeeman field in a Superconductor-Chiral Material Heterostructure

Authors: Cliff Chen, Jason Tran, Anthony McFadden, Raymond Simmonds, Keisuke Saito, En-De Chu, Daniel Morales, Varrick Suezaki, Yasen Hou, Joe Aumentado, Patrick A. Lee, Jagadeesh S. Moodera, Peng Wei

Abstract: A localized Zeeman field, intensified at heterostructure interfaces, could play a crucial role in a broad area including spintronics and unconventional superconductors. Conventionally, the generation of a local Zeeman field is achieved through magnetic exchange coupling with a magnetic material. However, magnetic elements often introduce defects, which could weaken or destroy superconductivity. Al… ▽ More A localized Zeeman field, intensified at heterostructure interfaces, could play a crucial role in a broad area including spintronics and unconventional superconductors. Conventionally, the generation of a local Zeeman field is achieved through magnetic exchange coupling with a magnetic material. However, magnetic elements often introduce defects, which could weaken or destroy superconductivity. Alternatively, the coupling between a superconductor with strong spin-orbit coupling and a non-magnetic chiral material could serve as a promising approach to generate a spin active interface. In this study, we leverage an interface superconductor, namely induced superconductivity in noble metal surface states, to probe the spin active interface. Our results unveil an enhanced interface Zeeman field, which selectively closes the surface superconducting gap while preserving the bulk superconducting pairing. The chiral material, i.e. trigonal tellurium, also induces Andreev bound states (ABS) exhibiting spin polarization. The field dependence of ABS manifests a substantially enhanced interface Landé g-factor (g_eff ~ 12), thereby corroborating the enhanced interface Zeeman energy. △ Less

Submitted 28 August, 2024; originally announced August 2024.

Comments: 27 pages, 11 figures

Journal ref: Science Advances 10, eado4875 (2024)

Robust Room-Temperature Polariton Condensation and Lasing in Scalable FAPbBr$_3$ Perovskite Microcavities

Authors: Mateusz Król, Mitko Oldfield, Matthias Wurdack, Eliezer Estrecho, Gary Beane, Yihui Hou, Andrew G. Truscott, Agustin Schiffrin, Elena A. Ostrovskaya

Abstract: Exciton-polariton condensation in direct bandgap semiconductors strongly coupled to light enables a broad range of fundamental studies and applications like low-threshold and electrically driven lasing. Yet, materials hosting exciton-polariton condensation in ambient conditions are rare, with fabrication protocols that are often inefficient and non-scalable. Here, room-temperature exciton-polarito… ▽ More Exciton-polariton condensation in direct bandgap semiconductors strongly coupled to light enables a broad range of fundamental studies and applications like low-threshold and electrically driven lasing. Yet, materials hosting exciton-polariton condensation in ambient conditions are rare, with fabrication protocols that are often inefficient and non-scalable. Here, room-temperature exciton-polariton condensation and lasing is observed in a microcavity with embedded formamidiniumlead bromide (FAPbBr$_3$) perovskite film. This optically active material is spin-coated onto the microcavity mirror, which makes the whole device scalable up to large lateral sizes. The sub-$μ$m granulation of the polycrystalline FAPbBr$_3$ film allows for observation of polariton lasing in a single quantum-confined mode of a polaritonic 'quantum dot'. Compared to random photon lasing, observed in bare FAPbBr$_3$ films, polariton lasing exhibits a lower threshold, narrower linewidth, and an order of magnitude longer coherence time. Both polariton and random photon lasing are observed under the conditions of pulsed optical pumping, and persist without significant degradation for up to 6 and 17 hours of a continuous experimental run, respectively. This study demonstrates the excellent potential of the FAPbBr$_3$ perovskite as a new material for room-temperature polaritonics, with the added value of efficient and scalable fabrication offered by the solution-based spin-coating process. △ Less

Submitted 24 July, 2024; originally announced July 2024.

Unusual charge density wave introduced by Janus structure in monolayer vanadium dichalcogenides

Authors: Ziqiang Xu, Yan Shao, Chun Huang, Genyu Hu, Shihao Hu, Zhi-Lin Li, Xiaoyu Hao, Yanhui Hou, Teng Zhang, Jin-An Shi, Chen Liu, Jia-Ou Wang, Wu Zhou, Jiadong Zhou, Wei Ji, Jingsi Qiao, Xu Wu, Hong-Jun Gao, Yeliang Wang

Abstract: As a fundamental structural feature, the symmetry of materials determines the exotic quantum properties in transition metal dichalcogenides (TMDs) with charge density wave (CDW). Breaking the inversion symmetry, the Janus structure, an artificially constructed lattice, provides an opportunity to tune the CDW states and the related properties. However, limited by the difficulties in atomic-level fa… ▽ More As a fundamental structural feature, the symmetry of materials determines the exotic quantum properties in transition metal dichalcogenides (TMDs) with charge density wave (CDW). Breaking the inversion symmetry, the Janus structure, an artificially constructed lattice, provides an opportunity to tune the CDW states and the related properties. However, limited by the difficulties in atomic-level fabrication and material stability, the experimental visualization of the CDW states in 2D TMDs with Janus structure is still rare. Here, using surface selenization of VTe2, we fabricated monolayer Janus VTeSe. With scanning tunneling microscopy, an unusual root13-root13 CDW state with threefold rotational symmetry breaking was observed and characterized. Combined with theoretical calculations, we find this CDW state can be attributed to the charge modulation in the Janus VTeSe, beyond the conventional electron-phonon coupling. Our findings provide a promising platform for studying the CDW states and artificially tuning the electronic properties toward the applications. △ Less

Submitted 17 June, 2024; originally announced June 2024.

Highly Efficient Superconducting Diodes and Rectifiers for Quantum Circuitry

Authors: Josep Ingla-Aynés, Yasen Hou, Sarah Wang, En-De Chu, Oleg A. Mukhanov, Peng Wei, Jagadeesh S. Moodera

Abstract: Superconducting electronics is essential for energy-efficient quantum and classical high-end computing applications. Towards this goal, non-reciprocal superconducting circuit elements, such as superconducting diodes (SDs) can fulfill many critical needs. SDs have been the subject of multiple studies, but integrating several SDs in a superconducting circuit remains a challenge. Here we implement th… ▽ More Superconducting electronics is essential for energy-efficient quantum and classical high-end computing applications. Towards this goal, non-reciprocal superconducting circuit elements, such as superconducting diodes (SDs) can fulfill many critical needs. SDs have been the subject of multiple studies, but integrating several SDs in a superconducting circuit remains a challenge. Here we implement the first SD bridge with multiple SDs exhibiting reproducible characteristics operating at temperatures of a few Kelvin. We demonstrate its functionality as a full wave rectifier using elemental superconductors and insulating ferromagnets, with efficiency up to 43%, and ac to dc signal conversion capabilities at frequencies up to 40 kHz. Our results show a pathway with a highly scalable thin film platform for nonreciprocal superconducting circuits. They could significantly reduce energy consumption as well as decohering thermal and electromagnetic noise in quantum computing. △ Less

Submitted 21 June, 2024; v1 submitted 17 June, 2024; originally announced June 2024.

Comments: 6 pages, 3 figures

Journal ref: Nat Electron 8, 411 (2025)

Above room-temperature two-dimensional ferromagnetic half-metals in Mn-based Janus magnets

Authors: Xiang-Fan Huang, Kang-Jie Li, Zequan Wang, Shi-Bo Zhao, Bing Shen, Zu-Xin Chen, Yusheng Hou

Abstract: Two-dimensional (2D) ferromagnets and their heterostructures offer fertile grounds for designing fascinating functionalities in ultra-thin spintronic devices. Here, by first-principles calculations, we report the discovery of energetically and thermodynamically stable 2D ferromagnets with very strong inplane magnetic anisotropy in MnXY (X = S, and Se; Y = Cl, Br and I) monolayers. Remarkably, we f… ▽ More Two-dimensional (2D) ferromagnets and their heterostructures offer fertile grounds for designing fascinating functionalities in ultra-thin spintronic devices. Here, by first-principles calculations, we report the discovery of energetically and thermodynamically stable 2D ferromagnets with very strong inplane magnetic anisotropy in MnXY (X = S, and Se; Y = Cl, Br and I) monolayers. Remarkably, we find that the Curie temperatures of the ferromagnetic MnSBr, MnSI, MnSeCl, and MnSeI monolayers are as high as 271, 273, 231 and 418 K, respectively. In addition, we demonstrate that these ferromagnetic monolayers are intrinsic half-metals with large spin band gaps ranging from 2.5 eV to 3.2 eV. When spin-orbit coupling is considered in these ferromagnetic monolayers, the nature of their half-metal is almost unaffected. Finally, the strong inplane magnetic anisotropy of MnSY (Y = Br, I) and MnSeY (Y = Cl, I) monolayers originate mainly from halogen and chalcogen atoms, respectively. Our work shows 2D Janus Mn-based ferromagnetic half-metals may have appealing functionalities in high-performance spintronic applications. △ Less

Submitted 9 June, 2024; originally announced June 2024.

Comments: 16 pages, 4 figures, accepted by Applied Physics Letters

Journal ref: Appl. Phys. Lett. 124, 252402 (2024)

Magnetic ground state of monolayer CeI$_{2}$: occupation matrix control and DFT+U calculations

Authors: Yue-Fei Hou, Shujing Li, Xinlong Yang, Wei Jiang, Qiuhao Wang, Fawei Zheng, Zhen-Guo Fu, Ping Zhang

Abstract: The magnetic ground state is crucial for the applications of the two-dimension magnets as it decides fundamental magnetic properties of the material, such as magnetic order, magnetic transition temperature, and low-energy excitation of the spin waves. However, the simulations for magnetism of local-electron systems are challenging due to the existence of metastable states. In this study, occupatio… ▽ More The magnetic ground state is crucial for the applications of the two-dimension magnets as it decides fundamental magnetic properties of the material, such as magnetic order, magnetic transition temperature, and low-energy excitation of the spin waves. However, the simulations for magnetism of local-electron systems are challenging due to the existence of metastable states. In this study, occupation matrix control (OMC) and density functional theory plus Hubbard $U$ calculations are applied to investigate the magnetic ground state of monolayer CeI$_{2}$. Following the predicted ferromagnetic (FM) order, the FM ground state and the FM metastable states are identified and found to have different values of the magnetic parameters. Based on the calculated magnetic parameters of the FM ground state, the Curie temperature is estimated to be $128$ K for monolayer CeI$_{2}$. When spin-orbit coupling (SOC) is considered, the FM ground state is further confirmed to contain both off-plane and in-plane components of magnetization. SOC is shown to be essential for reasonably describing not only magnetic anisotropy but also local electronic orbital state of monolayer CeI$_{2}$. △ Less

Submitted 5 December, 2024; v1 submitted 1 June, 2024; originally announced June 2024.

Comments: 4 figures. Accepted by Phys. Rev. B