Showing 1–50 of 435 results for author: Lu, X

Memory-dependent electronic friction for nonadiabatic dynamics at metal surfaces

Authors: Xuexun Lu, Connor L. Box, Nils Hertl, Reinhard J. Maurer

Abstract: Electronic excitation induced by nuclear motion is a key energy dissipation channel in chemical dynamics at metal surfaces. Here, nonadiabatic effects can be treated via molecular dynamics with electronic friction, where they act as frictional drag and fluctuation force contributions. Commonly, the Markov approximation is imposed, so memory effects are ignored. A theoretical formalism is presented… ▽ More Electronic excitation induced by nuclear motion is a key energy dissipation channel in chemical dynamics at metal surfaces. Here, nonadiabatic effects can be treated via molecular dynamics with electronic friction, where they act as frictional drag and fluctuation force contributions. Commonly, the Markov approximation is imposed, so memory effects are ignored. A theoretical formalism is presented to evaluate tensorial and configuration-dependent electronic friction memory kernels from first principles. We evaluate friction kernels for Newns--Anderson Hamiltonian models as well as within Kohn--Sham density functional theory and analyse their mathematical properties and configuration dependence. For hyperthermal atomic and diatomic scattering, memory effects arising from frequency and configuration dependence of electronic friction affect energy exchange between adsorbate and metal electrons. Memory effects lead to an increase of vibrational and a reduction of translational energy loss in the case of nitric oxide scattering on Au(111), leading to an increase of directional anisotropy of friction. Importantly, memory-dependent evaluation of electronic friction removes the need to define a single effective Markovian friction coefficient from the structured frequency-dependent electronic response. △ Less

Submitted 12 August, 2026; originally announced August 2026.

Comments: 22 pages, 7 figures

Emergent trans-moiré orbitals and topology in rhombohedral graphene

Authors: Yuqin Wang, Jian Xie, Yi-Jie Wang, Jiajun Zhang, Yiting Gao, Zaizhe Zhang, Da Yi, Yan Xie, Jingjing Shi, Guanqin Zhao, Chengyu Xiong, Kenji Watanabe, Takashi Taniguchi, Zhi-Da Song, Xiaobo Lu, Yi Chen

Abstract: The fractional quantum anomalous Hall effect (FQAHE) exhibited in fractional Chern insulators has recently been demonstrated in twisted MoTe2 and rhombohedral graphene/hBN moiré superlattices, promising new routes toward topological quantum computation. Central to realizing this promise is the understanding of the underlying microscopic mechanism. This, however, remains elusive in the case of rhom… ▽ More The fractional quantum anomalous Hall effect (FQAHE) exhibited in fractional Chern insulators has recently been demonstrated in twisted MoTe2 and rhombohedral graphene/hBN moiré superlattices, promising new routes toward topological quantum computation. Central to realizing this promise is the understanding of the underlying microscopic mechanism. This, however, remains elusive in the case of rhombohedral graphene, with the crux being its two seemingly paradoxical conditions: a pronounced small-twist-angle (θ) moiré interface, yet only when electrons are kept distant from it. Here, by scanning tunnelling microscopic imaging with both conditions fulfilled, we capture dramatic electronic structure reshaping in rhombohedral hexalayer graphene by unforeseen 'trans-moiré orbitals', which emerge on the other, distant side of the moiré interface but nevertheless enforce the moiré periodicity at all measured fillings. We visualize a hierarchy of spatially and energetically distinct trans-moiré orbitals which doped electrons must sequentially occupy--the lowest-energy orbital, expectedly responsible for the FQAHE at small fillings, carries a hollow-cage-like shape. Remarkably, these trans-moiré orbitals vanish at θ {\gtrsim} 1°, and so do QAHE plateaus in similar devices. Simulations reveal an interaction-driven charge-redistribution mechanism which shapes the trans-moiré orbitals and corresponding Chern minibands. With our findings providing the missing microscopic link, the paradoxical conditions find a natural explanation: electrons are not simply kept distant from a small-θ moiré interface; they are forced into topological trans-moiré orbitals, forged precisely under such conditions. Our microscopic diagnostics unlocks a wide range of possible 'synthetic' FQAHE platforms. △ Less

Submitted 19 August, 2026; v1 submitted 12 August, 2026; originally announced August 2026.

Gradient-based optimization of non-Abelian fractional quantum states in patterned superlattices

Authors: Yifei Guan, Lichen Yu, Zizhuang Liu, Xin Lu, Jianpeng Liu

Abstract: The realization of fractional Chern insulator (FCI) states in moiré heterostructures has attracted intense interest in the study of correlated states emerging from topological flat bands. So far, most experimentally realized FCI states may be interpreted as lattice analogues of fractional quantum Hall (FQH) states hosting Abelian anyonic excitations. Realizing non-Abelian FCI states is an importan… ▽ More The realization of fractional Chern insulator (FCI) states in moiré heterostructures has attracted intense interest in the study of correlated states emerging from topological flat bands. So far, most experimentally realized FCI states may be interpreted as lattice analogues of fractional quantum Hall (FQH) states hosting Abelian anyonic excitations. Realizing non-Abelian FCI states is an important challenge in the field. Patterned dielectric superlattices provide a versatile platform for engineering topological flat bands. Such systems offer substantial structural flexibility and tunability, because their lattice patterns, periods, and other structural parameters can all be designed and fabricated. Here we propose to realize non-Abelian FCI states in patterned dielectric superlattices coupled to bilayer graphene. Specifically, we provide a realistic workflow based on a gradient-descent algorithm to design non-Abelian fractional states in bilayer graphene superlattices. The experimentally relevant structural parameters of the superlattices are gradient-optimized to favor a flat Chern band with quantum-geometric properties reminiscent of those of the first excited Landau level. Exact diagonalization calculations at 1/2 filling of the optimized flat Chern band naturally yield non-Abelian FCI states. We apply this workflow to triangular, honeycomb, and kagome patterned superlattices and find robust non-Abelian FCI states over a large region of the parameter space spanned by the superlattice constant and vertical potential drop. Our work thus establishes an experimentally feasible framework for exploring non-Abelian FCIs in realistic patterned-superlattice devices. It also demonstrates the potential of device-level inverse design to engineer correlated topological matter beyond the Abelian paradigm. △ Less

Submitted 10 August, 2026; originally announced August 2026.

Pressure induced magnetic-field-free superconducting diode effect in NbSe2 flake

Authors: Shihao Zhu, Tian Le, Cuiying Pei, Changhua Li, Yi Liao, Yi Zhao, Lingxiao Zhao, Qi Wang, Juefei Wu, Qilian Zhang, Yueshen Wu, Tonghuan Fu, Xujie Lü, Wenge Yang, Jie Shen, Jun Li, Yulin Chen, Xiao Lin, Wen-Yu He, Yanpeng Qi

Abstract: The superconducting diode effect (SDE) is a fascinating nonreciprocal phenomenon where the critical current is different for opposite current directions. It is widely believed that realizing SDE requires breaking both inversion symmetry (IS) and time-reversal symmetry (TRS), which are usually achieved via heterostructure engineering and applying external magnetic fields. Here, we report a pressure… ▽ More The superconducting diode effect (SDE) is a fascinating nonreciprocal phenomenon where the critical current is different for opposite current directions. It is widely believed that realizing SDE requires breaking both inversion symmetry (IS) and time-reversal symmetry (TRS), which are usually achieved via heterostructure engineering and applying external magnetic fields. Here, we report a pressure-induced magnetic-field-free SDE in NbSe2 flakes without any heterostructures. We show that pressure alone breaks the IS, as confirmed by the second harmonic generation. Crucially, upon applying an out-of-plane magnetic field (B), the SDE exhibits even-in-B behavior, implying the absence of explicit TRS breaking. This finding challenges the prevailing theoretical paradigm and demonstrates that a magnetic-field-free SDE can emerge without explicitly breaking TRS. Thereby, our work establishes pressure engineering as a powerful tool for inducing nonreciprocal superconductivity and designing versatile, magnetic-field-free superconducting devices. △ Less

Submitted 3 August, 2026; originally announced August 2026.

Comments: 10 pages,4 figues

Journal ref: Phys. Rev. Lett. 137, 076003 (2026)

$d$-spacing distributions as a probe of nematoelastic response in iron-based superconductors

Authors: Wenting Zhang, Ruixian Liu, Tingjun Zhang, Weiliang Yao, Xüe Fu, Hanqing Xie, Ziye Mo, Ting Guo, Kuo-Feng Tseng, Thomas Keller, Jitae T. Park, Fankang Li, Masaaki Matsuda, Avishek Maity, Long Tian, Pengcheng Dai, Xingye Lu

Abstract: Electronic nematicity in iron-based superconductors (FeSCs) couples bilinearly to orthorhombic strain, allowing nematic correlations to appear in the lattice response. Here we use neutron Larmor diffraction to measure the temperature-dependent distribution of relative $d$ spacings in electron-doped Ba(Fe$_{1-x}$Co$_x$)$_2$As$_2$, hole-doped Ba$_{0.83}$K$_{0.17}$Fe$_2$As$_2$, FeSe, and Fe$_{1.07}$T… ▽ More Electronic nematicity in iron-based superconductors (FeSCs) couples bilinearly to orthorhombic strain, allowing nematic correlations to appear in the lattice response. Here we use neutron Larmor diffraction to measure the temperature-dependent distribution of relative $d$ spacings in electron-doped Ba(Fe$_{1-x}$Co$_x$)$_2$As$_2$, hole-doped Ba$_{0.83}$K$_{0.17}$Fe$_2$As$_2$, FeSe, and Fe$_{1.07}$Te. In Ba(Fe$_{1-x}$Co$_x$)$_2$As$_2$ crystals without intentionally applied uniaxial stress, the in-plane distribution width, $\varepsilon_{\rm FWHM}$, increases on cooling in the tetragonal phase and can be described phenomenologically by a Curie--Weiss-like form. The fitted scale $T^*$ decreases with Co doping and evolves similarly to the nematic phase diagram inferred from elastoresistance, although the two experiments probe different response functions. Related broadening in Ba$_{0.83}$K$_{0.17}$Fe$_2$As$_2$ and FeSe supports extending this interpretation beyond electron-doped BaFe$_2$As$_2$. By contrast, Fe$_{1.07}$Te shows no extended Curie--Weiss-like regime without applied stress, whereas uniaxial pressure produces a strongly anisotropic broadening that can contain contributions from both the field-biased lattice response and inhomogeneous loading. A mean-field model with bilinear nematoelastic coupling and spatially varying symmetry-breaking stress explains the Curie--Weiss-like broadening in terms of the renormalized orthorhombic compliance. Neutron Larmor diffraction therefore provides a bulk-sensitive probe of nematic-related lattice broadening that complements electronic and elastic measurements. △ Less

Submitted 2 August, 2026; originally announced August 2026.

Comments: 9 pages, 4 figures

"Anomalous Solid Solution" in Ultra-High Melting Point Oxides: A New Strategy for Developing Ultra-High Temperature Thermal Protection Coatings

Authors: Yubo Wang, Hong Meng, Pengfei He, Shujun Hu, Chuan Sun, Ximing Duan, Xiaopeng Lu, Dingwang Yuan, Wangyu Hu, Xiubing Liang

Abstract: The high-temperature performance of ultra-high temperature ceramics (UHTCs) in atmospheric environment is fundamentally governed by their melting points of oxidation products. Typical high-melting-point oxides, such as ZrO2, undergo phase transformations at elevated temperatures, leading to structural instability. Although doping with rare-earth or transition-metal cations can suppress these trans… ▽ More The high-temperature performance of ultra-high temperature ceramics (UHTCs) in atmospheric environment is fundamentally governed by their melting points of oxidation products. Typical high-melting-point oxides, such as ZrO2, undergo phase transformations at elevated temperatures, leading to structural instability. Although doping with rare-earth or transition-metal cations can suppress these transformations, it often results in a reduction in melting point, thereby limiting practical service temperature. Here, ytterbia-stabilized zirconia (YbSZ) coatings are prepared via atmospheric plasma spraying, achieving a remarkable increase in the melting point of ZrO2 to approximately 2850 $^\circ\mathrm{C}$ and raising the ultimate plasma and oxyacetylene ablation temperature up to nearly 2780 $^\circ\mathrm{C}$ and 3200 $^\circ\mathrm{C}$, which is the highest temperature resistance property as reported. Notably, this performance enhancement originates from a synergistic mechanism of strengthened ionic-covalent mixed bonding and improved oxygen vacancy stability. Based on these findings, the concept of "anomalous solid solution" is firstly proposed to be used in the area of ultra-high temperature protection, which provides new insights into the compositional design of UHTC systems. △ Less

Submitted 30 July, 2026; originally announced July 2026.

Unconventional and Fragile Magnetic Exciton in a van der Waals Quantum Magnet

Authors: Kai-Xuan Zhang, Min Zhang, Minjae Kim, Yong-Hyun Kim, Junghyun Kim, Heejun Yang, Pyeongjae Park, Chaebin Kim, Mangesh Diware, Junik Hwang, Youjin Lee, Byeong-Gwan Cho, Hyeong-Do Kim, Tae-Yeong Koo, Chunhua Chen, Mingtao Li, Xujie Lü, Wenge Yang, Kee-Hoon Kim, Seung-Ho Baek, Hyeonsik Cheong, Sung-Keun Lee, Beom Hyun Kim, Christopher Lane, Jian-Xin Zhu , et al. (3 additional authors not shown)

Abstract: The recently discovered magnetic exciton in the van der Waals (vdW) antiferromagnet NiPS3 exemplifies these phenomena, exhibiting several distinctive characteristics. Despite extensive investigation, much of its physics remains unresolved, with key questions about why the NiPS3 magnetic exciton is so sharp and optically bright despite the nominally spin-forbidden transition, posing significant cha… ▽ More The recently discovered magnetic exciton in the van der Waals (vdW) antiferromagnet NiPS3 exemplifies these phenomena, exhibiting several distinctive characteristics. Despite extensive investigation, much of its physics remains unresolved, with key questions about why the NiPS3 magnetic exciton is so sharp and optically bright despite the nominally spin-forbidden transition, posing significant challenges to a proper understanding and practical manipulation of the exciton. An urgent question is to what extent it is due to chemical disorder, magnetic weakening, lattice modification, or intrinsic instability of the bright exciton itself: answers to which will put stringent constraints on possible theoretical models. Here we address these questions using hydrostatic pressure as a clean, continuous, reversible, and in-situ tuning parameter. We find that the sharp photoluminescence peak is drastically suppressed by as little as 0.4 GPa and completely quenched by 1.5 GPa, with demonstrating its reversibility. Crucially, this bright-to-dark conversion occurs without magnetic, crystallographic, or electronic reconstruction despite an increase in the Neel temperature, as established by Raman, X-ray absorption, nuclear magnetic resonance spectroscopy, and first-principles many-body calculations. Our results demonstrate that the optical brightness of the magnetic exciton is independent of chemical disorder, lattice expansion, and weakening of magnetic order, indicating that a higher-order correlated mechanism governs the bright exciton. We further propose experimentally constrained microscopic scenarios involving exciton pairing, crystal-field-controlled spin-orbit mixing, and symmetry breaking, providing a framework for future tests of entangled magnetic exciton in correlated quantum magnets. △ Less

Submitted 30 July, 2026; originally announced July 2026.

Comments: Our findings indicate that the sharp coherence of the entangled magnetic exciton benefits from its delicate quantum nature, and its optical brightness can be activated by exciton pairing or spin-orbit coupling, while its fragility under external control is achievable through a high-order perturbation rather than a first-order transition

$c$-axis strain tuning of superconductivity and symmetric elastoresistivity in CsV$_3$Sb$_5$

Authors: Xiaoran Yang, Yutong Li, Chunyi Li, Qi Tang, Jiawen Zhang, Yu Song, Huiqiu Yuan, Xingye Lu

Abstract: The kagome metal CsV$_{3}$Sb$_{5}$ hosts an intriguing interplay between charge-density-wave (CDW) order and superconductivity that is highly sensitive to lattice distortions. However, determining the specific roles of the in-plane ($A_{1g,1}$) and out-of-plane ($A_{1g,2}$) symmetric strain channels has been hindered by their intrinsic mixing in conventional piezo-based experiments. Here, we combi… ▽ More The kagome metal CsV$_{3}$Sb$_{5}$ hosts an intriguing interplay between charge-density-wave (CDW) order and superconductivity that is highly sensitive to lattice distortions. However, determining the specific roles of the in-plane ($A_{1g,1}$) and out-of-plane ($A_{1g,2}$) symmetric strain channels has been hindered by their intrinsic mixing in conventional piezo-based experiments. Here, we combine in-plane uniaxial strain with direct $c$-axis compression to independently access and disentangle these symmetry-resolved responses in CsV$_{3}$Sb$_{5}$. We reveal that $c$-axis compression drives a massive, linear enhancement of the superconducting transition temperature ($T_c$) alongside a suppression of $T_{\rm CDW}$. The tuning efficiency of this out-of-plane deformation acts with an opposite sign and far exceeds that of in-plane strain, demonstrating that $c$-axis lattice control dictates the phase competition. Furthermore, by isolating the pure elastoresistivity coefficients, we find that the out-of-plane cross-coupling coefficient ($m_{13}$) is comparable in magnitude but opposite in sign to the in-plane response ($m_{11}+m_{12}$). Unlike the sharply peaked in-plane response, $m_{13}$ exhibits a distinct, order-parameter-like onset across the CDW transition. Our results establish that out-of-plane lattice control plays a dominant role in tuning the intertwined states in CsV$_{3}$Sb$_{5}$ and provide a general pathway for resolving strain-coupled electronic responses in layered quantum materials. △ Less

Submitted 16 July, 2026; originally announced July 2026.

Comments: 8 pages, 4 figures

Iron-Based Superconductors: A Decade of Materials, Magnetism, and Mechanisms

Authors: Xingye Lu, Hechang Lei, Jun Zhao, Hideo Hosono, Pengcheng Dai

Abstract: Since its discovery in 2008, iron-based superconductors (FeSCs) have become a central platform for exploring high-temperature superconductivity in multiband, electron-correlated materials. This review focuses on major developments over the past decade or so, emphasizing experimental advances, pairing mechanisms, and emerging applications. Structural tuning through chemical substitution, pressure,… ▽ More Since its discovery in 2008, iron-based superconductors (FeSCs) have become a central platform for exploring high-temperature superconductivity in multiband, electron-correlated materials. This review focuses on major developments over the past decade or so, emphasizing experimental advances, pairing mechanisms, and emerging applications. Structural tuning through chemical substitution, pressure, and epitaxial growth enables precise control of the electronic, magnetic, and superconducting ground states, thereby revealing their interplay. In particular, the electronic nematic phase and stripe-type antiferromagnetic order-often coexisting or competing-are central to understanding the phase diagrams. Spin waves in magnetically ordered parent compounds and spin excitations (fluctuations) in doped superconductors are extensively characterized by inelastic neutron scattering. While high-energy spin excitations in doped superconductors retain substantial spectral weight across a wide energy range reminiscent of spin waves in their undoped parents, the low-energy response reveals a collective spin excitation termed "resonance" coupled to superconductivity. The momentum structure of superconductivity-induced resonance provides strong evidence for sign-changing pairing in many FeSCs, while disorder effects, orbital-fluctuation scenarios, quasiparticle damping, and compound-dependent gap structures indicate that $s_{\pm}$, $s_{++}$, nodal $s$, $d$-wave, and multicomponent states must be discussed in a material-specific framework. Advances in thin-film growth, intercalation chemistry, and interface engineering-particularly in FeSe-based systems-have enabled enhanced $T_{c}$ and novel device geometries. With high upper critical fields, moderate anisotropy, and improving current densities, FeSCs continue to drive both fundamental insight and technological applications in superconductivity. △ Less

Submitted 15 July, 2026; v1 submitted 13 July, 2026; originally announced July 2026.

Comments: 73 pages, 43 figures, 3 tables

Soft point-contact Andreev reflection spectroscopy in a palm-type cubic anvil-pressure cell

Authors: Qingxin Dong, Fengrui Shi, Yan Zhang, Tong Shi, Yi Liu, Shaoheng Ruan, Zhongjin Wu, Jianping Sun, Zhaoming Tian, Yoshiya Uwatoko, Guanghan Cao, Xin Lu, Bosen Wang, Jin-Guang Cheng

Abstract: We have implemented soft point-contact Andreev reflection spectroscopy (PCARS) in a palm-type cubic anvil pressure cell by combining a substrate anchoring strategy with an external wire-splitting technique. This design enables the stable formation of multiple point contact junctions under hydrostatic pressures up to 15 GPa. Benchmark measurements on the elemental superconductor Nb demonstrate high… ▽ More We have implemented soft point-contact Andreev reflection spectroscopy (PCARS) in a palm-type cubic anvil pressure cell by combining a substrate anchoring strategy with an external wire-splitting technique. This design enables the stable formation of multiple point contact junctions under hydrostatic pressures up to 15 GPa. Benchmark measurements on the elemental superconductor Nb demonstrate high reproducibility and yield a zero-temperature superconducting gap with a gap ratio of 3.3. We further apply this technique to the Kagome metal superconductor CsCr3Sb5 and the bilayer nickelate superconductor La2PrNi2O7. Pronounced zero-bias conductance peaks are observed, and their evolution with temperature, magnetic field and applied pressure is investigated, together with the superconducting gap magnitude and possible pairing symmetries. These measurements provide spectroscopic evidence consistent with unconventional superconductivity in these materials. Our work establishes a robust experimental platform that bridges macroscopic electrical transport and microscopic spectroscopic probes, opening a new avenue for investigating pairing symmetry in a wide range of pressure-induced unconventional superconductors. △ Less

Submitted 12 July, 2026; originally announced July 2026.

Comments: 16 pages, 4 figures

Electric-Field Switchable Magnetic Spin Hall Effect

Authors: Mingbo Dou, Xu Chen, Qin Zhang, Xianjie Wang, Xue-Zeng Lu, Jia Zhang, L. L. Tao

Abstract: It is established that the polarity of a time-reversal-odd ($\mathcal{T}$-odd) physical quantity can be reversed under the $\mathcal{T}$ operation. Here, we use the spin-group analysis to directly demonstrate that the $\mathcal{T}$-odd magnetic spin Hall effect in ferroelectric altermagnets can be switchable by electric fields beyond the $\mathcal{T}$ operation. This arises from the ferroelectric… ▽ More It is established that the polarity of a time-reversal-odd ($\mathcal{T}$-odd) physical quantity can be reversed under the $\mathcal{T}$ operation. Here, we use the spin-group analysis to directly demonstrate that the $\mathcal{T}$-odd magnetic spin Hall effect in ferroelectric altermagnets can be switchable by electric fields beyond the $\mathcal{T}$ operation. This arises from the ferroelectric switching of the nonrelativistic spin splitting, which swaps the roles of spin up and down channels in the reciprocal space. As a result, the $\mathcal{T}$-odd spin conductivity that are proportional to the spin-polarized conductivity difference reverses its polarity upon polarization switching. We identify spin-group operations to switch both the polarization and the magnetic spin Hall effect simultaneously for non-centrosymmetric spin point groups. Then, we exemplify those phenomena in the ferroelectric altermagnet VOI$_2$ monolayer based on density functional theory calculations and an effective Hamiltonian analysis. Our findings not only provide novel strategies to switch the magnetic spin Hall effect using the dissipation-free electric field but also open a promising avenue for electrically programmable spintronic devices. △ Less

Submitted 25 June, 2026; originally announced June 2026.

Charge imprinting biases topology of correlated insulator in hBN-aligned rhombohedral multilayer graphene

Authors: Lei Qiao, Xin Lu, Fu-Chun Zhang, Jianpeng Liu

Abstract: Rhombohedral multilayer graphene aligned with hexagonal boron nitride (RMG-hBN) hosts correlated Chern phases, but the microscopic role of hBN stacking remains unclear, especially when the active carriers are displaced away from the moiré interface. Using Hartree-Fock calculations over layer numbers, twist angles, displacement fields, fillings, and hBN alignments, we show that correlated insulator… ▽ More Rhombohedral multilayer graphene aligned with hexagonal boron nitride (RMG-hBN) hosts correlated Chern phases, but the microscopic role of hBN stacking remains unclear, especially when the active carriers are displaced away from the moiré interface. Using Hartree-Fock calculations over layer numbers, twist angles, displacement fields, fillings, and hBN alignments, we show that correlated insulators are most robust at small twist angles and intermediate layer number ($N\simeq 6$), where bandwidth suppression is balanced by layer delocalization of the wavefunctions of the active carriers. Under moiré-distant conditions at filling $ν=1$, the topology of the insulating state is strongly biased by charge imprinting: the hBN alignment shapes the occupied valence-band charge texture near the interface via moiré potential, which acts through long-range Coulomb interactions as a remote electrostatic template for doped conduction electrons. Depending on the alignment, this template favors either triangular charge localization associated with trivial insulators or honeycomb-like charge networks compatible with Chern insulators. Our results identify valence-band charge textures as a microscopic route by which a remote moiré interface controls correlated topology in multilayer graphene. △ Less

Submitted 18 June, 2026; originally announced June 2026.

Tunable Flat Bands and magnetism in Triangulene-based Superatomic Graphene

Authors: Wenya Zhai, Tingfeng Zhang, Fengkun Chen, Xiuqin Lu, Yunlong Xia, Zengfu Ou, Ye Chen, Donghui Guo, Meifang Zhu, Zhengfei Wang, Jingcheng Li

Abstract: Superatomic graphene platforms host a rich portfolio of flat-band-driven exotic quantum properties, yet their experimental realization remains challenging. Here, we report the bottom-up on-surface synthesis of superatomic graphene using phosphorus-doped triangulene as building blocks. Scanning tunneling microscopy and spectroscopy measurements resolve the well-defined honeycomb lattice of as-fabri… ▽ More Superatomic graphene platforms host a rich portfolio of flat-band-driven exotic quantum properties, yet their experimental realization remains challenging. Here, we report the bottom-up on-surface synthesis of superatomic graphene using phosphorus-doped triangulene as building blocks. Scanning tunneling microscopy and spectroscopy measurements resolve the well-defined honeycomb lattice of as-fabricated superatomic graphene and demonstrate the characteristic Dirac band and flat band electronic structures. Density functional theory calculations reveal that the flat bands originate from the in-plane p$_x,_y$-like frontier orbitals of the phosphorus-doped triangulene units, leading to intrinsic half-metallic behavior. Furthermore, oxygen functionalization of the molecular precursor enables deterministic modulation of the electronic structure and magnetic ordering. This work establishes a general platform for designing correlated quantum materials with tunable flat band properties. △ Less

Submitted 18 June, 2026; originally announced June 2026.

Comments: arXiv admin note: substantial text overlap with arXiv:2411.01108

Enhanced electronic correlations and altermagnetic ground state of two-dimensional CsCr3Sb5 monolayers

Authors: Z. H. Guan, Z. L. Peng, W. Z. Zhuo, G. Tian, Z. P. Hou, D. Y. Chen, Z. Fan, X. B. Lu, X. S. Gao, M. H. Qin, J. M. Liu

Abstract: Recently, layered corrected kagome metal CsCr3Sb5 have garnered significant attention attributed to its flat bands near the Fermi level (EF) and altermagnetic ground state [ Yi Liu et al., Nature 632, 1032 (2024)]. However, the van Hove singularities (vHSs) in bulk CsCr3Sb5 are far away from the EF, while an effective modulation of VHS toward the EF is essential for exploring intriguing electron t… ▽ More Recently, layered corrected kagome metal CsCr3Sb5 have garnered significant attention attributed to its flat bands near the Fermi level (EF) and altermagnetic ground state [ Yi Liu et al., Nature 632, 1032 (2024)]. However, the van Hove singularities (vHSs) in bulk CsCr3Sb5 are far away from the EF, while an effective modulation of VHS toward the EF is essential for exploring intriguing electron transport properties. In this work, using first-principles calculations, we investigate electronic structures of two-dimensional (2D) Cr3Sb5 and CsCr3Sb5 monolayers which may be mechanically exfoliated from bulk materials. Notably, it is revealed that both flat bands and vHSs simultaneously reside in close proximity to the EF in Cr3Sb5 monolayer, signifying enhanced electronic correlations. Importantly, a tensile strain further shifts the incipient flat bands and vHSs of two monolayers simultaneously to the vicinity of the EF, suggesting strain tunable electronic correlations and concomitant quantum effects. Furthermore, altermagnetic ground state is also revealed due to retained mirror symmetry between two sublattices in these two monolayers. Thus, this work advances understanding and modulations of electronic properties of 2D CsCr3Sb5 monolayers, strengthening their great potential for exploring unconventional quantum phenomena and altermagnetism. △ Less

Submitted 17 June, 2026; originally announced June 2026.

Comments: 22 pages, 5 figures

Andreev Reflection to Probe Momentum-Dependent Spin Polarization in Altermagnet CrSb

Authors: Yan Zhang, Yixuan Luo, Yue Yang, Zilong Li, Weilong Qiu, Lunhui Hu, Yuanfeng Xu, Yanfeng Guo, Chao Cao, Xin Lu

Abstract: Altermagnetic materials have recently emerged as promising candidates for next-generation spintronic applications, characterized by the k-dependent spin-splitted band structure and a simultaneous zero-net-magnetization. Among them, altermagnetic candidate CrSb has attracted considerable attention, owing to its g-wave spin splitting and high Néel temperature. In this article, we employed mechanical… ▽ More Altermagnetic materials have recently emerged as promising candidates for next-generation spintronic applications, characterized by the k-dependent spin-splitted band structure and a simultaneous zero-net-magnetization. Among them, altermagnetic candidate CrSb has attracted considerable attention, owing to its g-wave spin splitting and high Néel temperature. In this article, we employed mechanical point-contact spectroscopy (MPCS) with superconducting Nb tips to probe the Andreev reflection on CrSb single crystals along three principal crystallographic orientations. The extracted momentum-dependent spin polarizations are approximately 73.4% for the (0001) plane, 67.9% for the (-1-120) plane, and 61.9% for the (10-10) plane, respectively, distinct from conventional antiferromagnets. Furthermore, conductance spectra from spatial line-scans on the sample surface support the existence of altermagnetic domains with a characteristic size of 250-500 nm separated by domain-walls with width about 250 nm. These results strongly support the momentum-dependent spin polarization in altermagnetic CrSb and establish Andreev reflection as a new paradigm to probe k-dependent spin textures. △ Less

Submitted 11 June, 2026; originally announced June 2026.

Comments: 7 pages, 5 figures

Journal ref: PRL(2026)

Many-Body Non-Hermitian Physics in the Generalized Brillouin Zone

Authors: Chaoze Lu, Chuanshu Xu, Zhenghao Yang, Xiancong Lu

Abstract: The breakdown of conventional bulk-boundary correspondence (BBC) in non-Hermitian system can be resolved by the generalized Brillouin zone (GBZ) theory. However, extending the GBZ theory to interacting many-body systems remains an open problem. Here, we consider an interacting non-Hermitian model characterized by a circular GBZ. We show that, based on a GBZ transformation, a quasi-recipr… ▽ More The breakdown of conventional bulk-boundary correspondence (BBC) in non-Hermitian system can be resolved by the generalized Brillouin zone (GBZ) theory. However, extending the GBZ theory to interacting many-body systems remains an open problem. Here, we consider an interacting non-Hermitian model characterized by a circular GBZ. We show that, based on a GBZ transformation, a quasi-reciprocal many-body Hamiltonian can be constructed which, under periodic boundary conditions (PBC), captures the physics of the original non-Hermitian model under open boundary conditions (OBC). Using exact diagonalization (ED), we determine the phase diagram for the quasi-reciprocal many-body Hamiltonian by computing the Zak phase and the structure factor of the charge-density-wave (CDW) phase. We further investigate the entanglement properties and find that the degeneracy of the low-lying entanglement spectrum characterizes each phase in the phase diagram. These findings demonstrate that the topological properties in interacting non-Hermitian system is encoded in the entanglement spectrum of the quasi-reciprocal model. Our work establishes a route to studying many-body non-Hermitian physics within the GBZ formalism. △ Less

Submitted 2 June, 2026; originally announced June 2026.

Comments: 5 pages, 4 figures

Negative temperature coefficient of Gilbert damping in magnetic bilayers

Authors: Lulu Cao, Yuting Gong, Xianyang Lu, Yongbing Xu, Ya Zhai, Jing Wu, Roy W. Chantrell, Richard F. L. Evans

Abstract: The Gilbert damping of magnetic materials is an important magnetic parameter that determines the switching speed and energy dissipation of spintronic devices. In simple metals, the intrinsic Gilbert damping increases with temperature and diverges near the Curie temperature as a result of spin fluctuations. Here we present atomistic simulations and experimental measurements showing surprising and o… ▽ More The Gilbert damping of magnetic materials is an important magnetic parameter that determines the switching speed and energy dissipation of spintronic devices. In simple metals, the intrinsic Gilbert damping increases with temperature and diverges near the Curie temperature as a result of spin fluctuations. Here we present atomistic simulations and experimental measurements showing surprising and opposite behavior in Py/Nd bilayers, where the Gilbert damping decreases with increasing temperature. The effect arises because of the enhanced damping at the interface as a result of spin pumping, where elevated temperatures cause a dynamic separation of the interfacial and bulk magnetization during relaxation. Furthermore, the temperature dependence of the damping can be controlled by varying the thickness of the Nd capping layer. Our findings present a new spintronic effect that can be used to modify the dynamic properties of nanoscale materials and devices for enhanced energy efficiency or with improved switching dynamics. △ Less

Submitted 1 June, 2026; originally announced June 2026.

Winding feature and thermal evolution of the Dirac magnons in CrI$_3$

Authors: Weiliang Yao, Matthew B. Stone, Colin L. Sarkis, Yi Li, Ruixian Liu, Xingye Lu, Pengcheng Dai

Abstract: Two-dimensional honeycomb lattice ferromagnet chromium tri-iodide (CrI$_3$) has attracted tremendous interest because it retains ferromagnetism down to the monolayer limit and hosts intriguing topological magnons. As a prototypical van der Waals magnet, CrI$_3$ provides an ideal platform for exploring the interplay between reduced dimensionality, magnetic order, and nontrivial spin excitations. He… ▽ More Two-dimensional honeycomb lattice ferromagnet chromium tri-iodide (CrI$_3$) has attracted tremendous interest because it retains ferromagnetism down to the monolayer limit and hosts intriguing topological magnons. As a prototypical van der Waals magnet, CrI$_3$ provides an ideal platform for exploring the interplay between reduced dimensionality, magnetic order, and nontrivial spin excitations. Here, using inelastic neutron scattering together with improved sample quality, we uncover the magnon winding feature around the $K$-point of the hexagonal Brillouin zone, a key signature of Dirac magnons. In addition, we find that the magnon energy follows a $T^2$-renormalization behavior at elevated temperatures, consistent with magnon-magnon interactions. These results provide previously missing information on the magnon spectrum of CrI$_3$ and further consolidate the topological nature of its spin excitations. △ Less

Submitted 7 May, 2026; originally announced May 2026.

Universal Design Principles for High-Quality Persistent Spin Textures

Authors: Cheng-Ao Ji, Lingling Tao, James M. Rondinelli, Xue-Zeng Lu

Abstract: Persistent spin texture (PST) describes a unique spin-momentum locking in momentum space that maintains a uniform spin orientation through portions of the Brillouin zone (BZ), enabling exceptionally long spin lifetimes which are essential for applications in spintronics. However, materials exhibiting large BZ regions of high-quality PST, characterized by minimal spin deviation and long spin lifeti… ▽ More Persistent spin texture (PST) describes a unique spin-momentum locking in momentum space that maintains a uniform spin orientation through portions of the Brillouin zone (BZ), enabling exceptionally long spin lifetimes which are essential for applications in spintronics. However, materials exhibiting large BZ regions of high-quality PST, characterized by minimal spin deviation and long spin lifetimes, remain scarce. Here a universal model is introduced to capture the formation of superior PST regions arising from the interplay of spin-orbit fields at different k points. Within this framework, high-quality PSTs are identified in several systems belonging to various point groups. Notably, the nonpolar-chiral compound Na2Sn2O3 exhibits ~0.02 Å-2 high-quality PST region, which can be reversed by the switching of geometric chirality, while AgClO4 (D2d symmetry) exhibits a 0.016 Å-2 PST region. Significantly, Na2Sn2O3 and AgClO4 host persistent spin helices with spin lifetimes of 0.5-7.4 ns and 0.9-2.5 ns, respectively, among the longest reported for PST materials. In addition, both chemical substitutions and the application of pressure are demonstrated as effective routes for engineering high-quality PST. Our findings not only establish a universal principle for high-quality PST, but also provide promising materials across various point groups for the next-generation spintronic devices. △ Less

Submitted 3 May, 2026; originally announced May 2026.

Experimental measurements and modeling of characteristic time scales in single iron particle ignition

Authors: Liulin Cen, Yong Qian, XiaoCheng Mi, Xingcai Lu

Abstract: Recyclable metal fuels such as iron are promising carbon-free energy carriers for heat and power. In such systems, particle ignition characteristics strongly affect combustion efficiency and combustor stability, making them critical for burner and reactor design. However, predictive ignition modelling remains limited by the lack of time-resolved data for single-particle solid-phase oxidation and p… ▽ More Recyclable metal fuels such as iron are promising carbon-free energy carriers for heat and power. In such systems, particle ignition characteristics strongly affect combustion efficiency and combustor stability, making them critical for burner and reactor design. However, predictive ignition modelling remains limited by the lack of time-resolved data for single-particle solid-phase oxidation and phase transitions. In this work, digital in-line holography combined with ultra-high-speed single-color pyrometry is used to resolve characteristic solid-phase oxidation times of spherical micron-sized iron particles burning in well-defined hot oxidizing environments. Three temperature plateaus are identified, corresponding to FeO melting, the γ-Fe to δ-Fe transition, and Fe melting, from which pre-melting oxidation times and melting durations are extracted. An ignition model based on solid-phase iron oxidation kinetics following a parabolic rate law, coupled with external-oxygen-transport-limited description, is used to simulate these characteristic times. The model accurately captures the FeO-scale pre-melting oxidation time, which is nearly independent of oxygen concentration, while the FeO, γ-Fe to δ-Fe, and Fe melting stages show strong oxygen-concentration dependence consistent with external-oxygen-transport-limited reaction rates. These measurements and simulations provide the first diameter-resolved dataset for FeO and Fe melting processes and show that this modelling framework can quantitatively predict characteristic times for single iron particles in metal-fuel applications. △ Less

Submitted 6 April, 2026; originally announced April 2026.

Comments: 14 pages, 19 figures

GHz control of THz QCL band structure and gain by standing acoustic strain

Authors: Alexander S. Kuznetsov, Valentino Pistore, Lutz Schrottke, Klaus Biermann, Xiang Lü

Abstract: Active frequency comb generation and waveform control are central challenges in the terahertz (THz) domain. In THz quantum cascade lasers (QCLs), these functions have typically been achieved through active bias modulation, which alters the operating point of the device and imposes severe limitations on its flexibility. To address these challenges, we propose an approach based on the direct modulat… ▽ More Active frequency comb generation and waveform control are central challenges in the terahertz (THz) domain. In THz quantum cascade lasers (QCLs), these functions have typically been achieved through active bias modulation, which alters the operating point of the device and imposes severe limitations on its flexibility. To address these challenges, we propose an approach based on the direct modulation of the QCL bandstructure using GHz-frequency standing bulk acoustic waves (BAWs), promising direct and localized control of the optical gain and chromatic dispersion. To this end, we fabricated a bulk acoustic transducer on top of a THz QCL in order to excite GHz standing BAWs within its active region. We demonstrate that radio-frequency driving of the transducer leads to the tunable generation of standing BAWs in 5-12 GHz frequency range with wavelengths commensurate to the QCL period length. The effect of the BAW on the QCL bandstructure is revealed by measuring photoluminescence (PL) of the active region, where the BAW strain leads to a considerable modulation of the PL energy up to a few meV around its non-modulated value. We also develop a model and perform bandstructure simulations to predict the effect of the BAW on the QCL subband structure and gain. These results mark the first demonstration of dynamic bandstructure modulation in a THz QCL using GHz acoustic strain, introducing a fundamentally new paradigm that establishes a powerful synergy between QCLs and BAWs towards coherent control and frequency comb engineering in the THz domain. △ Less

Submitted 24 March, 2026; originally announced March 2026.

Observation of a Reconstructed Chern Insulator in Twisted Bilayer MoTe2

Authors: Min Wu, Lingxiao Li, Yunze Ouyang, Yifan Jiang, Wenxuan Qiu, Zaizhe Zhang, Zihao Huo, Qiu Yang, Ming Tian, Neng Wan, Kenji Watanabe, Takashi Taniguchi, Shiming Lei, Fengcheng Wu, Xiaobo Lu

Abstract: Twisted bilayer MoTe2 is a prototypical moire material in which long-wavelength superlattices amplify electron correlations, enabling a wealth of emergent quantum phases. To date, experimental efforts have focused primarily on small twist angles (typically smaller than 4deg ), whereas the larger-angle regime-where moire bands become more dispersive and correlations are reduced-has remained largely… ▽ More Twisted bilayer MoTe2 is a prototypical moire material in which long-wavelength superlattices amplify electron correlations, enabling a wealth of emergent quantum phases. To date, experimental efforts have focused primarily on small twist angles (typically smaller than 4deg ), whereas the larger-angle regime-where moire bands become more dispersive and correlations are reduced-has remained largely unexplored. Here we chart the topological phase space of tMoTe2 at a relatively large twist angle of approximately 4.54deg, accessing a moderately correlated regime with enhanced bandwidth. In contrast to small-angle devices that predominantly host fractional quantum anomalous Hall or spin Hall responses, we uncover multiple Chern-insulating states with C = 1 at moire fillings v = -1, -0.53 and -1/2. Strikingly, at v = -2/3 a magnetic field induces a fractional Chern insulator accompanied by an insulator-metal transition. Our results broaden the topological phase diagram of tMoTe2 and establish large-angle moire superlattices as a versatile platform for engineering robust topological states beyond the strong-correlation limit. △ Less

Submitted 17 March, 2026; originally announced March 2026.

Offer of a reward does not always promote trust in spatial games

Authors: Haidong Zhang, Chaoqian Wang, Shuo Liu, Charo I. del Genio, Stefano Boccaletti, Xin Lu

Abstract: Trust is one of the cornerstones of human society. One of the evolutionary pressure mechanisms that may have led to its emergence is the presence of incentives for trustworthy behavior. However, this type of reward has received relatively little attention in the context of spatial trust games, which are often used to build models in evolutionary game theory. To fill this gap, we introduce an inter… ▽ More Trust is one of the cornerstones of human society. One of the evolutionary pressure mechanisms that may have led to its emergence is the presence of incentives for trustworthy behavior. However, this type of reward has received relatively little attention in the context of spatial trust games, which are often used to build models in evolutionary game theory. To fill this gap, we introduce an inter-role reward mechanism in the spatial trust game, so that an investing trustor can choose to pay an extra cost to reward a trustworthy trustee. With extensive numerical simulations, we find that this type of reward does not always promote trust. Rather, while moderate rewards break the dominance of mistrust, thereby favoring investment, excessive rewards eventually stimulate a nonreturn strategy, ultimately suppressing the evolution of trust. Additionally, lower reward costs do not necessarily promote trust. Instead, more costly, but not excessive, rewards enhance the advantage of the original investment, consolidating the clusters of rewarders and improving trust. Our model thus provides evidence about the counterintuitive nature of the relationship between trust and rewards in a complex society. △ Less

Submitted 7 March, 2026; originally announced March 2026.

Comments: 25 pages, 9 figures, accepted for publication in Physical Review Research

Percolation-driven $β$ -relaxation enables resonant acceleration of crystallization in amorphous phase-change materials

Authors: Yu-Yao Liu, Liang Gao, Jun-Ying Jiang, Yiming Zhou, Jan Luebben, Di Zhao, Xiaoling Lu, Maximilian J. Müller, Ulrich Boettger, Jiang-Jing Wang, Hai-Bin Yu, Shuai Wei

Abstract: Amorphous phase-change materials enable fast and reversible switching in optical and electronic devices, yet crystallization kinetics are still controlled primarily through empirical thermal protocols. Here we identify a microscopic picture governing crystallization in the prototypical phase-change material Ge2Sb2Te5, in which crystallization pathways are organized by the percolation of mobile ato… ▽ More Amorphous phase-change materials enable fast and reversible switching in optical and electronic devices, yet crystallization kinetics are still controlled primarily through empirical thermal protocols. Here we identify a microscopic picture governing crystallization in the prototypical phase-change material Ge2Sb2Te5, in which crystallization pathways are organized by the percolation of mobile atomic networks associated with $β$-relaxation. We show that this percolation transition distinguishes the dominance of diffusion-driven and diffusionless nucleation and growth during crystallization processes. We further demonstrate that frequency-selected ultrasonic excitation, applied in conjunction with heating, accelerates crystallization by enhancing percolation-mediated atomic dynamics. This acceleration is maximized near the $β$-relaxation frequency, consistent with resonant excitation of mobile atoms. Our results establish a direct link between glassy relaxation, atomic-scale percolation, and crystallization, and introduce a new route to modulating phase-change kinetics through targeted excitation of fundamental glassy dynamics. △ Less

Submitted 2 March, 2026; originally announced March 2026.

Comments: 17 pages,4 figures

Doping evolution of spin excitations in La$_{3-x}$Sr$_{x}$Ni$_2$O$_7$/SrLaAlO$_4$ superconducting thin films

Authors: Hengyang Zhong, Bo Hao, Anni Chen, Xinru Huang, Chunyi Li, Wenting Zhang, Chang Liu, Yuxun Zhu, Dao-Xin Yao, Kurt Kummer, Nicholas Brookes, Yuefeng Nie, Thorsten Schmitt, Xingye Lu

Abstract: Ambient-pressure superconductivity in compressively strained bilayer nickelate films provides a unique platform to test pairing scenarios, yet the evolution of magnetism with carrier doping remains largely unexplored. Here, we utilize Ni $L_3$-edge resonant inelastic x-ray scattering to systematically track the evolution of spin and electronic excitations in coherently strained La$_{3-x}$Sr$_x$Ni… ▽ More Ambient-pressure superconductivity in compressively strained bilayer nickelate films provides a unique platform to test pairing scenarios, yet the evolution of magnetism with carrier doping remains largely unexplored. Here, we utilize Ni $L_3$-edge resonant inelastic x-ray scattering to systematically track the evolution of spin and electronic excitations in coherently strained La$_{3-x}$Sr$_x$Ni$_2$O$_7$/SrLaAlO$_4$ thin films, spanning the superconducting ($x \le 0.21$) and overdoped non-superconducting ($x = 0.38$) regimes. We reveal that dispersive spin excitations, characterized by double-stripe correlations and nearly doping-independent exchange scales, persist robustly throughout the entire superconducting dome. In stark contrast, upon entering the overdoped non-superconducting state, this coherent magnetic framework undergoes an abrupt collapse, melting into a heavily damped, low-spectral-weight continuum. We show that this magnetic breakdown is fundamentally driven by a selective doping-induced orbital reconstruction. While the invariant $\sim\!1.0$~eV intra-atomic $dd$ peak confirms an intact local octahedral crystal field, the concurrent quenching of the $\sim\!0.4$~eV and $\sim\!1.6$~eV features signifies a severe degradation of the apical-oxygen-mediated $d_{z^2}$--$p_z$--$d_{z^2}$ singlet sector and bilayer charge-transfer coherence. The synchronized demise of coherent spin excitations and macroscopic pairing establishes a direct, doping-controlled link, underscoring that maintaining the localized $d_{z^2}$ magnetic framework and robust apical-oxygen coupling is the fundamental prerequisite for high-$T_c$ superconductivity in bilayer nickelates. △ Less

Submitted 9 June, 2026; v1 submitted 1 March, 2026; originally announced March 2026.

Comments: 9 pages, 4 figures, Supplemental material is available upon reasonable request

Mechanically Assisted Symmetry Reconstruction for Extraordinary Piezoelectricity

Authors: Jinhui Fan, Chonghe Wang, Xiaoyan Lu, Yunpeng Ma, Zijian Hong, Yuzhao Qi, Yanzhe Dong, Xiaoyue Zhang, Chuchu Yang, Yongchun Zou, Xu Zheng, Xiaolong Li, Qian Li, Xiang Xu, Si-Young Choi, Jiyan Dai, Wenwu Cao, Dragan Damjanovic, Hui Li

Abstract: Active symmetry control - a central challenge in materials science, particularly in ferroelectrics - is achieved via mechanically assisted poling (MAP) guided by thermodynamics and phase - field modeling. This approach yields extraordinary piezoelectric coefficients (about 5,000 pC/N at 24 degC; 11,700 pC/N at 58 degC) together with about 65% optical transmittance in a classic relaxor ferroelectri… ▽ More Active symmetry control - a central challenge in materials science, particularly in ferroelectrics - is achieved via mechanically assisted poling (MAP) guided by thermodynamics and phase - field modeling. This approach yields extraordinary piezoelectric coefficients (about 5,000 pC/N at 24 degC; 11,700 pC/N at 58 degC) together with about 65% optical transmittance in a classic relaxor ferroelectric, Pb(Mg1/3Nb2/3)O3-PbTiO3. Mechanical suppression of undesirable phases stabilizes a reconstructed symmetry with highly ordered domains, verified by multiple characterization techniques. The strategy is validated across several distinct ferroelectric systems. To demonstrate its practical utility, we fabricate a transparent dual-modal wearable sensor integrating continuous blood pressure monitoring via piezoelectricity with photoplethysmographic SpO2 detection, enabling high-fidelity physiological tracking. This work establishes mechanically assisted symmetry reconstruction as a pathway to multifunctional optoelectronic materials and compact wearable health technologies. △ Less

Submitted 28 February, 2026; originally announced March 2026.

Comments: 14 pages, 5 figures plus Supplementary Materials

Pressure-induced superconductivity beyond magnetic quantum criticality in a Kondo ferromagnet

Authors: Yanan Zhang, Yongjun Zhang, Jiawen Zhang, Kaixin Ye, Dajun Su, Yanen Huang, Zhaoyang Shan, Jiyuan Li, Rui Li, Ye Chen, Xin Lu, Lin Jiao, Yu Liu, Michael Smidman, Frank Steglich, Huiqiu Yuan

Abstract: Quantum phase transitions are an established setting for emergent phenomena driven by strong electronic correlations, including strange metals and unconventional superconductivity. These have been explored extensively in Kondo lattice materials tuned to an antiferromagnetic quantum critical point (QCP), but superconductivity emerging near ferromagnetic quantum criticality is not yet observed, and… ▽ More Quantum phase transitions are an established setting for emergent phenomena driven by strong electronic correlations, including strange metals and unconventional superconductivity. These have been explored extensively in Kondo lattice materials tuned to an antiferromagnetic quantum critical point (QCP), but superconductivity emerging near ferromagnetic quantum criticality is not yet observed, and the conditions under which it occurs in proximity to ferromagnetism are undetermined. Here, we report a new setting for superconductivity in the ferromagnetic Kondo-lattice material Ce5CoGe2, where there is a ferromagnetic ground state at ambient pressure, which evolves to antiferromagnetism under applied pressures. The antiferromagnetic transition is suppressed to a zero-temperature QCP, which is accompanied by strange-metal behavior. Superconductivity does not occur at the QCP, but instead appears at pressures beyond the magnetic instability. These findings suggest that Ce5CoGe2 represents a distinct class of correlated materials exhibiting a unique scenario for the emergence of superconductivity, likely associated with unconventional pairing mechanisms beyond spin-fluctuations. △ Less

Submitted 10 February, 2026; originally announced February 2026.

Infinite Magnetoresistance and Vortex Coupling in the Pb/BSCCO Heterostructure

Authors: Weifan Zhu, Jiamin Yao, Shuntianjiao Ling, Shanyin Fu, Yifu Xu, Pengyue Xiong, Jiawen Zhang, Mengwei Xie, Yanan Zhang, Ye Chen, Huiqiu Yuan, Xin Lu, Qing-Hu Chen, Yang Liu

Abstract: Combining superconductivity with spintronics provides exciting opportunities to realize low-dissipation quantum devices. Here we report the synthesis, characterization and magnetotransport measurements of the Pb/Bi$_2$Sr$_2$CaCu$_2$O$_{8+δ}$ (BSCCO) superconducting heterostructures, where an insulating PbO$_{x}$ layer spontaneously forms at the interface. Non-volatile switching between superconduc… ▽ More Combining superconductivity with spintronics provides exciting opportunities to realize low-dissipation quantum devices. Here we report the synthesis, characterization and magnetotransport measurements of the Pb/Bi$_2$Sr$_2$CaCu$_2$O$_{8+δ}$ (BSCCO) superconducting heterostructures, where an insulating PbO$_{x}$ layer spontaneously forms at the interface. Non-volatile switching between superconducting (logical "0") and normal ("1") states in Pb films by an external field, i.e., infinite magnetoresistance (IMR), can be realized and are attributed to the strong trapping and pinning of vortices in BSCCO. Furthermore, butterfly-shaped hysteresis loops in magnetoresistance, pronounced resistance dips/jumps and thermal reset to superconducting states can be observed and are direct manifestations of the peculiar vortex dynamics in BSCCO and vortex coupling across the Pb/BSCCO interface. Our work demonstrates a simple and effective way to realize IMR through superconducting vortices and opens up new opportunities to study the vortex interactions across the superconducting interfaces. △ Less

Submitted 30 January, 2026; originally announced January 2026.

Comments: 9 pages, 4 figures, accepted by PRB

Correlated states in charge-transfer heterostructures based on rhombohedral multilayer graphene

Authors: Yanran Shi, Min Li, Xin Lu, Jianpeng Liu

Abstract: Charge transfer is a common phenomenon in van der Waals heterostructures with proper work function mismatch, which enables electrostatic gating to control band alignment and interlayer charge distributions. This provides a tunable platform for studying coupled bilayer correlated electronic systems. Here, we theoretically investigate heterostructures of rhombohedral multilayer graphene (RMG) and an… ▽ More Charge transfer is a common phenomenon in van der Waals heterostructures with proper work function mismatch, which enables electrostatic gating to control band alignment and interlayer charge distributions. This provides a tunable platform for studying coupled bilayer correlated electronic systems. Here, we theoretically investigate heterostructures of rhombohedral multilayer graphene (RMG) and an insulating substrate with gate-tunable band alignment. We first develop a self-consistent electrostatic theory for layer charge densities incorporating charge transfer, which reproduces the experimentally observed broadened and bent charge neutrality region. When the substrate's band edge has a much larger effective mass than RMG, its carriers may form a Wigner crystal at low densities. This generates a quantum superlattice that induces topological flat bands in the RMG layer through interlayer Coulomb interactions, which may further lead to Chern insulators driven by Coulomb interactions within the RMG layers. Conversely, with comparable effective masses, we find an interlayer excitonic insulator state at charge neutrality stabilized by interlayer Coulomb coupling. Our work establishes these charge-transfer heterostructures as a rich platform for topological and excitonic correlated states. △ Less

Submitted 28 July, 2026; v1 submitted 15 January, 2026; originally announced January 2026.

Comments: 5 pages main text, 18 pages Supplemental Materials

Multigap nodeless superconductivity in Dirac semimetal PdTe

Authors: Fengrui Shi, Weilong Qiu, Chufan Chen, Chunqiang Xu, Yan Zhang, Hao Zheng, Yuwei Zhou, Dongting Zhang, Mengwei Xie, Huiqiu Yuan, Shiyan Li, Yang Liu, Chao Cao, Xiaofeng Xu, Xin Lu

Abstract: PdTe has recently been reported to be a type-II Dirac semimetal while a bulk nodal and surface nodeless superconductivity (SC) has been claimed to coexist. In this work, we applied point-contact spectroscopy (PCS) method to systematically study the superconducting gap in PdTe single crystals with a SC transition temperature $T_{c}=4.3$ K. The obtained differential conductance curves show a common… ▽ More PdTe has recently been reported to be a type-II Dirac semimetal while a bulk nodal and surface nodeless superconductivity (SC) has been claimed to coexist. In this work, we applied point-contact spectroscopy (PCS) method to systematically study the superconducting gap in PdTe single crystals with a SC transition temperature $T_{c}=4.3$ K. The obtained differential conductance curves show a common deviation from a single-gap superconducting behavior and can be better fitted by a two-gap Blonder-Tinkham-Klapwijk model, suggesting the larger gap $Δ_{L}$ with $2Δ_{L}$=3.7 $k_{B}T_{c}$ and the smaller gap $Δ_S$ yielding $2Δ_{S}$=1.1-2.2 $k_{B}T_{c}$ with a weak interband scattering. The variations of conductance spectra among different contacts are proposed to be caused by the anisotropy of Fermi surface topology associated with different gaps. △ Less

Submitted 8 January, 2026; originally announced January 2026.

Comments: 6 pages,5 figures

Journal ref: Phys. Rev. B 112, 224518 Published 23 December, 2025

Multiple nodal superconducting phases and order-parameter evolution in pressurized UTe$_2$

Authors: Shuo Zou, Fengrui Shi, Zhuolun Qiu, Jialong Zhang, Yan Zhang, Weilong Qiu, Zhuo Wang, Hai Zeng, Yinina Ma, Zheyu Wu, Andrej Cabala, Michal Valiska, Ning Li, Zihan Yang, Kaixin Ye, Jiawen Zhang, Yanan Zhang, Kangjian Luo, Binbin Zhang, Alexander G. Eaton, Chaofan Zhang, Gang Li, Jianlin Luo, Wen Huang, Huiqiu Yuan , et al. (2 additional authors not shown)

Abstract: Spin-triplet superconductivity (SC) offers a unique avenue for realizing non-Abelian Majorana zero modes and thus the fault-tolerant topological quantum computation, and has attracted a broad audience for both fundamental research and potential applications. The recently discovered heavy-fermion spin-triplet superconductor candidate UTe$_2$ has sparked great interest for its ultrahigh upper critic… ▽ More Spin-triplet superconductivity (SC) offers a unique avenue for realizing non-Abelian Majorana zero modes and thus the fault-tolerant topological quantum computation, and has attracted a broad audience for both fundamental research and potential applications. The recently discovered heavy-fermion spin-triplet superconductor candidate UTe$_2$ has sparked great interest for its ultrahigh upper critical field and reentrant SC phases in the proximity to a field-polarized magnetic state. Despite extensive studies on the phase diagrams and competing orders induced by pressure and magnetic field, limited has been known about its SC order parameters and their evolution with these control parameters, largely due to the lack of appropriate symmetry-sensitive detections. Here, we report comprehensive point-contact spectroscopy measurements of pressurized UTe$_2$ on the (0~0~1) surface. The observation of Andreev bound state strongly suggests the presence of a $p_z$ component in the SC order parameters. Quantitative analysis based on an extended Blonder-Tinkham-Klapwijk model unveils $B_{2u}$ or $B_{3u}$ as the most likely representation for both ambient and pressurized UTe$_2$, and remarkably, the multiple SC phases can be distinguished by a single parameter $\langle Δ_{z}\rangle/\langleΔ_{x(y)}\rangle$, the relative weight between the $p_z$-wave and $p_{x(y)}$-wave pairings. These findings not only impose stringent constraints on the superconducting order parameter in UTe$_2$, but also provide key spectroscopic evidence for the existence of multiple SC phases tuned through pressure. △ Less

Submitted 5 January, 2026; originally announced January 2026.

Comments: 21+14 pages, 5+9 figures, 1+1 tables

Magnetic-Field-Driven Insulator-Superconductor Transition in Rhombohedral Graphene

Authors: Jian Xie, Zihao Huo, Zhimou Chen, Zaizhe Zhang, Kenji Watanabe, Takashi Taniguchi, Xi Lin, Xiaobo Lu

Abstract: Recent studies of rhombohedral multilayer graphene (RMG) have revealed a variety of superconducting states that can be induced or enhanced by magnetic fields, reinforcing RMG as a powerful platform for investigating novel superconductivity. Here we report an insulator-superconductor transition driven by in-plane magnetic fields B|| in rhombohedral hexalayer graphene. The upper critical in-plane fi… ▽ More Recent studies of rhombohedral multilayer graphene (RMG) have revealed a variety of superconducting states that can be induced or enhanced by magnetic fields, reinforcing RMG as a powerful platform for investigating novel superconductivity. Here we report an insulator-superconductor transition driven by in-plane magnetic fields B|| in rhombohedral hexalayer graphene. The upper critical in-plane field of 2T violates the Pauli limit, and an analysis based on isospin symmetry breaking supports a spin-polarized superconductor. At in-plane B = 0, such spin-polarized superconductor transitions into an insulator, exhibiting a thermally activated gap of 0.1 meV. In addition, we observe four superconducting states in the hole-doped regime, as well as phases with orbital multiferroicity near charge neutrality point. These findings substantially enrich the phase diagram of rhombohedral graphene and provide new insight into the microscopic mechanisms of superconductivity △ Less

Submitted 30 December, 2025; originally announced December 2025.

Magnetic field and pressure tuning of the heavy fermion antiferromagnet CePdIn

Authors: Bin Shen, Feng Du, Rui Li, Hang Su, Yasuyuki Shimura, Takahiro Onimaru, Kazunori Umeo, Xin Lu, Toshiro Takabatake, Michael Smidman, Huiqiu Yuan

Abstract: Frustrated Kondo lattices are ideal platforms for studying how both the Kondo effect and quantum fluctuations compete with the magnetic exchange interactions that drive magnetic ordering. Here, we investigate the effect of tuning the heavy-fermion compound CePdIn, which crystallizes in the geometrically frustrated ZrNiAl-type structure, using applied magnetic fields and hydrostatic pressure. At am… ▽ More Frustrated Kondo lattices are ideal platforms for studying how both the Kondo effect and quantum fluctuations compete with the magnetic exchange interactions that drive magnetic ordering. Here, we investigate the effect of tuning the heavy-fermion compound CePdIn, which crystallizes in the geometrically frustrated ZrNiAl-type structure, using applied magnetic fields and hydrostatic pressure. At ambient pressure, CePdIn exhibits two magnetic transitions, one at $T_{\rm{N}} \approx 1.65$ K and another at $T_{\rm{M}} \approx 1.15$ K, which are both suppressed by applied $c$-axis fields. Upon applying pressure in zero magnetic field, there is a non-monotonic evolution of $T_{\rm{N}}$, which decreases to 0.8 K at 2.3 GPa, before abruptly increasing to 1.5 K at 2.6 GPa. At higher pressures, $T_{\rm{N}}$ has a weak pressure dependence, and vanishes near 5 GPa. Together with the high-pressure phase being more robust to applied fields, these results suggest two distinct antiferromagnetic phases in CePdIn, which are separated near 2.6 GPa, and this change may be driven by the evolution of the underlying electronic structure due to enhanced Kondo hybridization under pressure. △ Less

Submitted 13 March, 2026; v1 submitted 27 December, 2025; originally announced December 2025.

Comments: 9 pages, 11 figures

Journal ref: Phys. Rev. B 113, 115130 (2026)

Fractional High-Chern Insulator in Twisted Rhombohedral Graphene

Authors: Zexu Li, Wenxuan Wang, Fajie Wang, Zaizhe Zhang, Qiu Yang, Kenji Watanabe, Takashi Taniguchi, X. C. Xie, Jie Wang, Kaihui Liu, Zhida Song, Xiaobo Lu

Abstract: The realization of fractional Chern insulators opens up the possibility of exploring fractionally charged excitations and anyonic statistics in the absence of a magnetic field. A central question is whether lattice-based systems can give rise to radically new states, distinct from those observed in traditional fractional quantum Hall systems. In this work, we investigate a new type of moiré flat b… ▽ More The realization of fractional Chern insulators opens up the possibility of exploring fractionally charged excitations and anyonic statistics in the absence of a magnetic field. A central question is whether lattice-based systems can give rise to radically new states, distinct from those observed in traditional fractional quantum Hall systems. In this work, we investigate a new type of moiré flat band system composed of Bernal bilayer graphene and rhombohedral tetralayer graphene. We discover an unprecedented richness of quantum anomalous Hall insulators with Chern numbers from C = 1 to C = 7 at v = 1 and around v = 3. Remarkably, we observe an exotic fractional Chern insulator with C = 7/3 around v = 2/3 which is beyond all known fractional Chern insulators described by either the Jain sequence or current high Chern theory. Our work expands the understanding of fractionally charged excitations beyond the Landau level basis and offers a new moire platform for exploring anyons. △ Less

Submitted 2 June, 2026; v1 submitted 25 December, 2025; originally announced December 2025.

Entangled Moire Chern Insulator in Rhombohedral Graphene

Authors: Zaizhe Zhang, Xi Chen, Kenji Watanabe, Takashi Taniguchi, Zhida Song, Xiaobo Lu

Abstract: Graphene-based moire superlattices exhibit novel quantum phenomena driven by pronounced interactions, leading to topological corrected states like orbital Chern insulators exhibiting quantum anomalous Hall effect (QAHE). Typically, intrinsic Chern insulators are stabilized at odd moiré fillings, as even fillings often result in valley-balanced, topologically trivial states at zero magnetic field.… ▽ More Graphene-based moire superlattices exhibit novel quantum phenomena driven by pronounced interactions, leading to topological corrected states like orbital Chern insulators exhibiting quantum anomalous Hall effect (QAHE). Typically, intrinsic Chern insulators are stabilized at odd moiré fillings, as even fillings often result in valley-balanced, topologically trivial states at zero magnetic field. In our work, we report the observation of an intrinsic Chern insulator with C = 1 state at moire filling v = 2 in rhombohedral octalayer graphene (R8G)/hBN moire superlattice. Observing such Chern insulators in particular with C = 1 at v = 2 is intriguing, as each moiré band carries Chern number C = 1 or -1. We further demonstrate such a state can originate from the entanglement between the low-energy moire flat bands and high-energy remote bands according to the Hartree-Fock calculation. Our findings extend the known topological phase diagram of rhombohedral multilayer graphene (RMG) moire systems and establish this platform as highly promising for investigating strong electron correlations and multiband hybridized transport. △ Less

Submitted 25 December, 2025; originally announced December 2025.

A Numerical Perspective on Moiré Superlattices: From Single-Particle Properties to Many-Body Physics

Authors: Xin Lu, Bo Xie, Jianpeng Liu

Abstract: Moiré superlattices in two-dimensional materials provide a versatile platform to explore strongly correlated and topological phases. This work presents a practical theoretical workflow for studying the correlated and topological states in moiré systems, combining continuum modeling, Hartree-Fock mean-field approximations, many-body perturbation theory, and exact diagonalizations. We focus on the n… ▽ More Moiré superlattices in two-dimensional materials provide a versatile platform to explore strongly correlated and topological phases. This work presents a practical theoretical workflow for studying the correlated and topological states in moiré systems, combining continuum modeling, Hartree-Fock mean-field approximations, many-body perturbation theory, and exact diagonalizations. We focus on the numerical implementation of these methods, emphasizing subtleties such as remote band effects, inhomogeneous and dynamical screening, double counting problem, etc., which are often swept under the rug in theoretical works. The workflow enables a systematic investigation of symmetry-breaking ground state properties, quasiparticle excitation properties and fractional Chern insulator phases emerging from moiré superlattices, providing insights that are directly relevant to experimental observations. By bridging technical details and physical interpretations, this work aims to guide both theorists and experimentalists in understanding and predicting correlated phenomena in moiré materials. △ Less

Submitted 7 December, 2025; originally announced December 2025.

Comments: Invited review for APL Computational Physics; main texts include 27 pages with 7 figures

Reststrahlen band and optical bandgaps in semiconducting CrN films

Authors: Duc V. Dinh, Xiang Lü, Oliver Brandt, Dilara Sen, Olivia Fairlamb, Frank Peiris, Farihatun Lima, Alexander Bordovalos, Suresh Chaulagain, Ambalanath Shan, Nikolas J. Podraza

Abstract: We present a comprehensive optical characterization of 200-nm-thick CrN(111) films grown simultaneously on Al$_2$O$_3$(0001) and AlN/Al$_2$O$_3$(0001) using plasma-assisted molecular beam epitaxy. Spectroscopic ellipsometry, spanning the far-infrared to ultraviolet range (0.04 - 5.5 eV), is conducted at room temperature to determine the optical constants $n$ and $k$ of the films. Spectral fits rev… ▽ More We present a comprehensive optical characterization of 200-nm-thick CrN(111) films grown simultaneously on Al$_2$O$_3$(0001) and AlN/Al$_2$O$_3$(0001) using plasma-assisted molecular beam epitaxy. Spectroscopic ellipsometry, spanning the far-infrared to ultraviolet range (0.04 - 5.5 eV), is conducted at room temperature to determine the optical constants $n$ and $k$ of the films. Spectral fits reveal two interband transitions at approximately 0.35 and 0.60 eV. In the infrared range, the ellipsometry data also reveals a pronounced Reststrahlen band stemming from transversal and longitudinal optical phonons at approximately 403 and 629 cm$^{-1}$, respectively. The relative static and high-frequency permittivities are estimated to be about 39 and 15, respectively. A Born effective charge of approximately 2.7, extracted from the far-infrared region, indicates that CrN is partially ionic. △ Less

Submitted 27 November, 2025; originally announced November 2025.

Lorentz Skew Scattering Nonreciprocal Magneto-Transport

Authors: Xiu Fang Lu, Xue-Jin Zhang, Naizhou Wang, Jin Cao, Dan Zhao, Hui Wang, Tao Wu, Xian Hui Chen, Shen Lai, Cong Xiao, Shengyuan A. Yang, Weibo Gao

Abstract: In materials with broken inversion symmetry, nonreciprocal magneto-transport (NRMT) manifests as a bilinear dependence of charge conductivity on applied electric (E) and magnetic (B) fields. This phenomenon is deeply rooted in symmetry and electronic quantum geometry, holding promise for novel rectification and detector technologies. Existing experimental studies generally attribute NRMT to Zeeman… ▽ More In materials with broken inversion symmetry, nonreciprocal magneto-transport (NRMT) manifests as a bilinear dependence of charge conductivity on applied electric (E) and magnetic (B) fields. This phenomenon is deeply rooted in symmetry and electronic quantum geometry, holding promise for novel rectification and detector technologies. Existing experimental studies generally attribute NRMT to Zeeman-driven mechanisms and exhibit quadratic scaling with conductivity. Here, we report a previously unknown NRMT microscopic mechanism - Lorentz skew scattering (LSK) - revealed through the discovery of an unprecedented quartic scaling law of NRMT as well as quantitative agreement between theory and experiment in BiTeBr. LSK emerges from the interplay of Lorentz force and skew scattering, bridging classical field effect to quantum scattering effect on the Fermi surface. We demonstrate that the LSK dominates NRMT in BiTeBr, and elucidate that this dominance over other possible contributions stems from high mobility and strong Rashba splitting. The finding of LSK mechanism is of unique importance because it unveils the leading NRMT effect in high-mobility systems and suggests a universal principle towards strong NRMT by enhancing electronic relaxation time in topological materials, rendering a new designing idea for low-dissipation rectifiers and high-performance quantum electronics. △ Less

Submitted 5 November, 2025; originally announced November 2025.

Comments: 20 pages, 4 figures

Single femtosecond laser pulse-driven ferromagnetic switching

Authors: Chen Xiao, Boyu Zhang, Xiangyu Zheng, Yuxuan Yao, Jiaqi Wei, Dinghao Ma, Yuting Gong, Rui Xu, Xueying Zhang, Yu He, Wenlong Cai, Yan Huang, Daoqian Zhu, Shiyang Lu, Kaihua Cao, Hongxi Liu, Pierre Vallobra, Xianyang Lu, Youguang Zhang, Bert Koopmans, Weisheng Zhao

Abstract: Light pulses offer a faster, more energy-efficient, and direct route to magnetic bit writing, pointing toward a hybrid memory and computing paradigm based on photon transmission and spin retention. Yet progress remains hindered, as deterministic, single-pulse optical toggle switching has so far been achieved only with ferrimagnetic materials, which require too specific a rare-earth composition and… ▽ More Light pulses offer a faster, more energy-efficient, and direct route to magnetic bit writing, pointing toward a hybrid memory and computing paradigm based on photon transmission and spin retention. Yet progress remains hindered, as deterministic, single-pulse optical toggle switching has so far been achieved only with ferrimagnetic materials, which require too specific a rare-earth composition and temperature conditions for technological use. In mainstream ferromagnet--central to spintronic memory and storage--such bistable switching is considered fundamentally difficult, as laser-induced heating does not inherently break time-reversal symmetry. Here, we report coherent magnetization switching in ferromagnets, driven by thermal anisotropy torque with single laser pulses. The toggle switching behavior is robust over a broad range of pulse durations, from femtoseconds to picoseconds, a prerequisite for practical applications. Furthermore, the phenomenon exhibits reproducibility in CoFeB/MgO-based magnetic tunnel junctions with a high magnetoresistance exceeding 110%, as well as the scalability down to nanoscales with remarkable energy efficiency (17 fJ per 100-nm-sized bit). These results mark a notable step toward integrating opto-spintronics into next-generation memory and storage technologies. △ Less

Submitted 31 October, 2025; originally announced October 2025.

Comments: 19 pages, 7 figures

Design and theory of switchable linear magnetoelectricity by ferroelectricity in Type-I multiferroics

Authors: Hui-Min Zhang, Cheng-Ao Ji, Tong Zhu, Hongjun Xiang, Hiroshi Kageyama, Shuai Dong, James M. Rondinelli, Xue-Zeng Lu

Abstract: We present a comprehensive theoretical investigation of magnetoelectric (ME) coupling mechanisms in 19 altermagnetic and 4 ferrimagnetic Type-I multiferroics using electronic band structure calculations with spin-orbit coupling, a first-principles ME response framework, and spin-space-group theory analysis. We formulate a universal scheme for realizing nonvolatile ME coupling in Type-I multiferroi… ▽ More We present a comprehensive theoretical investigation of magnetoelectric (ME) coupling mechanisms in 19 altermagnetic and 4 ferrimagnetic Type-I multiferroics using electronic band structure calculations with spin-orbit coupling, a first-principles ME response framework, and spin-space-group theory analysis. We formulate a universal scheme for realizing nonvolatile ME coupling in Type-I multiferroics, where two distinct pathways emerge, each dictated by spin-space symmetry. The first pathway is associated with switching of the spin splitting or the now familiar spin-momentum locking in reciprocal space, characteristic of some altermagnetic mul-tiferroics that exhibit coexisting antiferromagnetism and ferroelectricity. The second pathway involves real-space magnetization switching via electric polarization reversal, characterized by switchable components of the linear ME tensor, despite the traditionally weak coupling in Type-I systems due to the independent origins of magnetism and ferroelectricity. We demonstrate that these two intrinsic ME coupling mechanisms are mutually exclusive and propose thermodynami-cally stable compounds for experimentation. Our findings establish general design principles for controlling robust nonvolatile ME effects in multiferroic materials. △ Less

Submitted 20 October, 2025; originally announced October 2025.

Journal ref: Phys. Rev. Lett. 135, 176701 (2025)

Does Moire Matter? Critical Moire Dependence with Quantum Fluctuations in Graphene Based Integer and Fractional Chern Insulators

Authors: Zihao Huo, Wenxuan Wang, Jian Xie, Yves H. Kwan, Jonah Herzog-Arbeitman, Zaizhe Zhang, Qiu Yang, Min Wu, Kenji Watanabe, Takashi Taniguchi, Kaihui Liu, Nicolas Regnault, B. Andrei Bernevig, Xiaobo Lu

Abstract: Rhombohedral multilayer graphene has emerged as a powerful platform for investigating flat-band-driven correlated phenomena, yet most aspects remain not understood. In this work, we systematically study the moire-dependent band topology in rhombohedral hexalayer graphene. For the first time we demonstrate that the moire twist angle plays a crucial role in the formation of the moire Chern insulator… ▽ More Rhombohedral multilayer graphene has emerged as a powerful platform for investigating flat-band-driven correlated phenomena, yet most aspects remain not understood. In this work, we systematically study the moire-dependent band topology in rhombohedral hexalayer graphene. For the first time we demonstrate that the moire twist angle plays a crucial role in the formation of the moire Chern insulators in rhombohedral hexalayer graphene/hexagonal boron nitride (RHG/hBN) moire superlattices. In the moire-distant regime at filling factor v = 1, only systems with a twist angle θ < 1.1° exhibit an integer moire Chern insulator, while the fractional Chern insulator at v = 2/3 requires smaller twist angle to be stabilized. Our theoretical modelling, which includes quantum fluctuations and exact diagonalization results, suggests that mean-field theory, which has been widely adopted, does not explain the twist-angle dependence of the v = 1 phase diagram, and that correlation effects are crucial. Moreover, we realize two distinct stacking configurations ( /Xi=0 and /Xi=1) between graphene and hBN, and find that both cases can yield a Chern insulator at v = 1. Our experimental work upends the current mean-field paradigm, illuminates how quantum fluctuations and moiré effects shape the RHG/hBN phase diagram, and paves the way for future understanding and engineering of topological correlated states in rhombohedral graphene moire systems. △ Less

Submitted 17 October, 2025; originally announced October 2025.

Decoupling hydrodynamization from thermalization via nonlinear Boltzmann equation

Authors: Xingjian Lu, Shuzhe Shi

Abstract: The early thermalization puzzle arises from the unexpectedly early applicability of hydrodynamics in heavy-ion collisions. While hydrodynamics has traditionally been associated with the onset of local thermal equilibrium, its derivations -- whether microscopic or macroscopic -- rely instead on linearization around equilibrium. However, the linearization timescale -- the time at which a system's ev… ▽ More The early thermalization puzzle arises from the unexpectedly early applicability of hydrodynamics in heavy-ion collisions. While hydrodynamics has traditionally been associated with the onset of local thermal equilibrium, its derivations -- whether microscopic or macroscopic -- rely instead on linearization around equilibrium. However, the linearization timescale -- the time at which a system's evolution begins to follow a linearized equation -- has not been systematically investigated. In this work, we employ the spectral nonlinear Boltzmann equation -- the lowest-order truncation of the spectral Bogoliubov--Born--Green--Kirkwood--Yvon (BBGKY) hierarchy -- to analyze the timescales of linearization and thermalization under three distinct truncation schemes. The first two truncations allow for analytic treatment via recursive spectral equations, while the third requires numerical methods for generic initial conditions. The analysis is performed for a homogeneous, massless system with a constant differential cross section. For this simplified setup, we find a robust separation: the linearization time is consistently about half the thermalization time ($τ_{\mathrm{lin}}/τ_{\mathrm{therm}} \approx 1/2$). This separation of timescales suggests an explanation for the early applicability of hydrodynamics and points toward a possible quantitative resolution of the early thermalization puzzle. △ Less

Submitted 28 September, 2025; originally announced September 2025.

Comments: 28 pages, 5 figures

General Many-Body Perturbation Framework for Moiré Systems

Authors: Xin Lu, Yuanfan Yang, Zhongqing Guo, Jianpeng Liu

Abstract: Moiré superlattices host a rich variety of correlated topological states, including interaction-driven integer and fractional Chern insulators. A common approach to study interacting ground states at integer fillings is the Hartree-Fock mean-field method. However, this method neglects dynamical correlations, which often leads to an overestimation of spontaneous symmetry breaking and fails to provi… ▽ More Moiré superlattices host a rich variety of correlated topological states, including interaction-driven integer and fractional Chern insulators. A common approach to study interacting ground states at integer fillings is the Hartree-Fock mean-field method. However, this method neglects dynamical correlations, which often leads to an overestimation of spontaneous symmetry breaking and fails to provide quantitative descriptions of single-particle excitations. This work introduces a general many-body perturbation framework for moiré systems, combining all-band Hartree-Fock calculations with $GW$ quasiparticle corrections and random phase approximation (RPA) correlation energies. We apply this framework to hexagonal boron nitride aligned rhombohedral pentalayer graphene and magic-angle twisted bilayer graphene (MATBG). We show that incorporating RPA correlation energy and $GW$ self-energy corrections yields phase diagrams and single-particle spectra that quantitatively align with experimental measurements for both systems. Particularly, the ground state at charge neutrality of MATBG is predicted to be a nematic metal, which is stabilized over Kramers intervalley coherent insulator due to lower correlation energy. Our versatile framework provides a systematic beyond-mean-field approach applicable to generic moiré systems. △ Less

Submitted 15 April, 2026; v1 submitted 24 September, 2025; originally announced September 2025.

Comments: 5 pages, 3 figures; abstract and main text revised, all the figures replaced, and supp info also updated

Competing and Intertwined Orders in Boson-Doped Mott Antiferromagnets

Authors: Xin Lu, Jia-Xin Zhang, Lukas Homeier, Shou-Shu Gong, D. N. Sheng, Zheng-Yu Weng

Abstract: Inspired by the recent experimental advances in cold atom quantum simulators, we explore the experimentally implemented bosonic $t$-$t'$-$J$ model on the square lattice using large-scale density matrix renormalization group simulations. By tuning the doping level $δ$ and hopping ratio $t'/t$, we uncover six distinct quantum phases, several of which go far beyond the conventional paradigm of phase-… ▽ More Inspired by the recent experimental advances in cold atom quantum simulators, we explore the experimentally implemented bosonic $t$-$t'$-$J$ model on the square lattice using large-scale density matrix renormalization group simulations. By tuning the doping level $δ$ and hopping ratio $t'/t$, we uncover six distinct quantum phases, several of which go far beyond the conventional paradigm of phase-coherent superfluidity (SF) expected for bosonic systems. In particular, in the presence of antiferromagnetic (AFM) order, doped holes are tightly bound into pairs, giving rise to a pair density wave (PDW) phase at low doping and small $|t'/t|$, which is suppressed on the $t'<0$ side, resulting in a disordered PDW state that lacks coherence of either individual bosons or pairs. Upon further doping, bosons can regain phase coherence and form a SF* state, characterized by condensation at emergent incommensurate momenta concurrent with an incommensurate magnetic order. On the $t'>0$ side, the sign-induced kinetic frustration inherently disfavors local AFM correlations, leading to a phase separation in which doped holes cluster into ferromagnetic (FM) domains spatially separated by undoped AFM regions. Upon further doping, this inhomogeneous state evolves into a uniform SF + $xy$-FM phase. Finally, we propose a concrete experimental scheme to realize both signs of $t'/t$ in Rydberg tweezer arrays, with an explicit mapping between model parameters and experimentally accessible regimes. Our results reveal competing and intertwined orders in doped antiferromagnets, which are relevant to central issues in high-$T_c$ superconductivity, reflecting the frustrated interplay between doped holes and spin background. △ Less

Submitted 5 March, 2026; v1 submitted 18 September, 2025; originally announced September 2025.

Comments: 26 pages, 24 figures

Journal ref: Phys. Rev. Lett. 136, 096506 (2026)

Antiferromagnetic ordering and critical behavior induced giant magnetocaloric effect in distorted kagome lattice Gd$_3$BWO$_9$

Authors: Zhuoqun Wang, Xueling Cui, Tim Treu, Jiesen Guo, Xinyang Liu, Marvin Klinger, Christian Heil, Nvsen Ma, Xianlei Sheng, Zheng Deng, Xingye Lu, Xiancheng Wang, Wei Li, Philipp Gegenwart, Changqing Jin, Kan Zhao

Abstract: We synthesize the high-quality Gd$_3$BWO$_9$ single crystal and investigate its lowtemperature magnetic and thermodynamic properties. Below $T\rm_{N}$ = 1.08 K, the anisotropic behavior of magnetic susceptibilities reveals that the Gd$^{3+}$ moments exhibit the dominant antiferromagnetic coupling along the $c$-axis, while displaying a ferromagnetic arrangement in kagome plane. With pronounced magn… ▽ More We synthesize the high-quality Gd$_3$BWO$_9$ single crystal and investigate its lowtemperature magnetic and thermodynamic properties. Below $T\rm_{N}$ = 1.08 K, the anisotropic behavior of magnetic susceptibilities reveals that the Gd$^{3+}$ moments exhibit the dominant antiferromagnetic coupling along the $c$-axis, while displaying a ferromagnetic arrangement in kagome plane. With pronounced magnetic frustration, in adiabatic demagnetization refrigeration experiments starting from initial conditions of 9 T and 2 K, Gd$_3$BWO$_9$ polycrystal reaches a minimum temperature of 0.151 K, significantly lower than its $T\rm_{N}$. Due to the high density of Gd$^{3+}$ ions ($S$=7/2), the maximum magnetic entropy change reaches over 50 J kg$^{-1}$ K$^{-1}$ under fields up to 7 T in Gd$_3$BWO$_9$, nearly 1.5 times as large as commercial sub-Kelvin magnetic coolant Gd$_3$Ga$_5$O$_{12}$(GGG). The H-T phase diagram of Gd$_3$BWO$_9$ under $H$//$c$ exhibits field-induced critical behavior near the phase boundaries. This observation aligns with the theoretical scenario in which a quantum critical point acts as the endpoint of a line of classical second-order phase transitions. Such behavior suggests the importance of further investigations into the divergence of magnetic Grüneisen parameter in the vicinity of critical field at ultralow temperatures. △ Less

Submitted 14 September, 2025; originally announced September 2025.

Comments: This manuscript contains 5 figures, to appear in Phys. Rev. Mater soon

Journal ref: Phys. Rev. Mater. 9, 094407 (2025)

Strongly tilted field induced fractional quantized-drift in non-interacting system

Authors: Bo Zhu, Zhi Tan, Huilin Gong, Honghua Zhong, Xin-You Lü, Xiaoguang Wang

Abstract: Fractional quantized response appears to be a distinctive characteristic in interacting topological systems. Here, we discover a novel phenomenon of tilt-induced fractional quantize drift in non-interacting system constructed by a time-modulated superlattice subjected to a external time-independent gradient potential. Depending on the tilt strength, Rabi oscillations between adjacent lowest enegy… ▽ More Fractional quantized response appears to be a distinctive characteristic in interacting topological systems. Here, we discover a novel phenomenon of tilt-induced fractional quantize drift in non-interacting system constructed by a time-modulated superlattice subjected to a external time-independent gradient potential. Depending on the tilt strength, Rabi oscillations between adjacent lowest enegy bands caused by Landau-Zener tunneling, can induce that the one-cycle-averaged drift displacement is fraction, which is relate to the ratio of the sum of Chern numbers of multiple bands to the number of energy bands involved in Landau Zener tunneling. As representative examples, we construct fractional (1/3, 1/2) quantize drift only via adjusting period of lattice. The numerical simulations allow us to consider a realistic setup amenable of an experimental realization. Our findings will expand the research implications of both fractional quantize response and topological materials. △ Less

Submitted 8 September, 2025; originally announced September 2025.

Comments: 9 pages, 5 figures

Magnetic excitations in biaxial-strain detwinned $α$-RuCl$_{3}$

Authors: Yi Li, Yanyan Shangguan, Xinzhe Wang, Ruixian Liu, Chang Liu, Yongqi Han, Zhaosheng Wang, Christian Balz, Ross Stewart, Shun-Li Yu, Jinsheng Wen, Jian-Xin Li, Xingye Lu

Abstract: The honeycomb magnet $α$-RuCl$_{3}$ has been a leading candidate for realizing the Kitaev quantum spin liquid (QSL), but its intrinsic spin dynamics have remained obscured by crystal twinning. Here we apply biaxial anisotropic strain to detwin $α$-RuCl$_{3}$ single crystals and directly visualize the intrinsic magnetic excitations using inelastic neutron scattering. We discover that the low-energy… ▽ More The honeycomb magnet $α$-RuCl$_{3}$ has been a leading candidate for realizing the Kitaev quantum spin liquid (QSL), but its intrinsic spin dynamics have remained obscured by crystal twinning. Here we apply biaxial anisotropic strain to detwin $α$-RuCl$_{3}$ single crystals and directly visualize the intrinsic magnetic excitations using inelastic neutron scattering. We discover that the low-energy spin waves emerge from the $M$ points -- transverse to the magnetic Bragg peaks -- providing direct evidence of anisotropic magnetic interactions in $α$-RuCl$_{3}$. The intrinsic spin-wave spectrum imposes stringent constraints on the extended Kitaev Hamiltonian, yielding a refined, quantitatively consistent set of exchange couplings for the zigzag ground state and its low-energy dynamics. Above the magnon band, we uncover broad excitation continua: while a twofold-symmetric feature near 6 meV at $Γ$ is consistent with bimagnon scattering, the dominant spectral weight forms a sixfold-symmetric continuum extending up to $\sim 16$ meV that cannot be explained by conventional magnons. This strongly supports the presence of fractionalized excitations-a hallmark of Kitaev QSL physics. Our findings establish biaxial strain as a powerful symmetry-breaking probe to access the intrinsic spin dynamics of Kitaev materials and provide critical benchmarks for refining theoretical models of quantum magnetism in $α$-RuCl$_{3}$. △ Less

Submitted 8 September, 2025; originally announced September 2025.

Comments: 8 pages, 4 figures

Spin Splitting Nernst Effect in Altermagnet

Authors: Xing-Jian Yi, Yue Mao, Xiancong Lu, Qing-Feng Sun

Abstract: Altermagnet is a distinctive magnet phase, which has spin-split energy band but with zero net magnetic moment. In this paper, we propose that altermagnet behaves spin splitting Nernst effect: Under a longitudinal temperature gradient, the electrons with opposite spins tend to split oppositely in the transverse direction, thus generating a transverse spin current. The spin splitting Nernst effect i… ▽ More Altermagnet is a distinctive magnet phase, which has spin-split energy band but with zero net magnetic moment. In this paper, we propose that altermagnet behaves spin splitting Nernst effect: Under a longitudinal temperature gradient, the electrons with opposite spins tend to split oppositely in the transverse direction, thus generating a transverse spin current. The spin splitting Nernst effect is understood from the contribution of the longitudinal wave vector to the transverse group velocity. Using the nonequilibrium Green's function method, we calculate the spin-dependent transmission coefficient in the four-terminal altermagnet device. From the spin-dependent transmission coefficient, the nonzero transverse spin current from longitudinal temperature gradient is obtained, and the spin splitting Nernst effect is verified. We systematically study the parameter dependence of the spin splitting Nernst effect, while also performing symmetry analysis. The spin splitting Nernst effect can be easily regulated by Fermi surface energy, temperature, transport direction, and system size. Furthermore, in altermagnet, the $xy$-response and $yx$-response spin splitting Nernst coefficients are equal with $N_{s,xy}=N_{s,yx}$, different from the conventional spin Nernst effect where they are opposite. Meanwhile, the spin splitting Nernst effect require neither spin-orbit coupling nor net magnetism. △ Less

Submitted 3 September, 2025; originally announced September 2025.

Journal ref: Phys. Rev. B 111, 035423 (2025)

Signatures of three-state Potts nematicity in spin excitations of the van der Waals antiferromagnet FePSe$_3$

Authors: Weiliang Yao, Viviane Peçanha Antonio, Devashibhai Adroja, S. J. Gomez Alvarado, Bin Gao, Sijie Xu, Ruixian Liu, Xingye Lu, Pengcheng Dai

Abstract: In two-dimensional (2D) nearly square-lattice quantum materials, electron correlations can induce an electronic nematic phase with twofold rotational ($C_2$) symmetry that profoundly impacts their properties. For 2D materials with threefold rotational ($C_3$) symmetry, such as the honeycomb lattice, a vestigial three-state Potts nematic order has been observed in the van der Waals antiferromagnet… ▽ More In two-dimensional (2D) nearly square-lattice quantum materials, electron correlations can induce an electronic nematic phase with twofold rotational ($C_2$) symmetry that profoundly impacts their properties. For 2D materials with threefold rotational ($C_3$) symmetry, such as the honeycomb lattice, a vestigial three-state Potts nematic order has been observed in the van der Waals antiferromagnet (AFM) FePSe$_3$ via optical and thermodynamic methods under uniaxial strain. Here, we use neutron scattering to study the magnetic order and spin excitations of FePSe$_3$ under uniaxial strain. In the AFM ordered state, we find that $\sim$0.6% tensile strain significantly suppresses one zigzag domain and promotes the other two, lowering the AFM order and spin waves to $C_2$ symmetry. The broken $C_3$ symmetry in spin excitations persists slightly above $T_{\rm{N}}\approx 108.6$ K, where the zigzag AFM order is absent. Our results thus provide direct evidence of magnetoelastic coupling and suggest that the three-state Potts nematicity in paramagnetic spin excitations arises from the vestigial order associated with the low-temperature zigzag AFM order. △ Less

Submitted 2 September, 2025; originally announced September 2025.

Piezomagnetism-driven magnetoelectric coupling in altermagnetic multiferroic K3Cr2F7

Authors: Ying Zhou, Hui-Min Zhang, Cheng-Ao Ji, Hongjun Xiang, Shuai Dong, James M. Rondinelli, Xue-Zeng Lu

Abstract: Ferroelectric control of altermagnetism in momentum space has been studied widely, while the control of magnetism in real space of altermagnets are still rare. We present a design rule to identify multiferroicity in n=2 Ruddlesden-Popper halides. Our results show that a Jahn-Teller distortion can cooperate with oxygen octahedral rotations to break inversion symmetry, which we demonstrate in K3Cr2F… ▽ More Ferroelectric control of altermagnetism in momentum space has been studied widely, while the control of magnetism in real space of altermagnets are still rare. We present a design rule to identify multiferroicity in n=2 Ruddlesden-Popper halides. Our results show that a Jahn-Teller distortion can cooperate with oxygen octahedral rotations to break inversion symmetry, which we demonstrate in K3Cr2F7 and cation-ordered KAg2Cu2Cl7, and leads to a ferrielectric-to-ferroelectric phase transition in K3Cr2F7. Altermagnetic spin order in the ferrielectric phase of K3Cr2F7 transforms into a conventional antiferromagnetic order in the ferroelectric phase, at which strain/pressure engineered sizable changes of weak ferromagnetism can occur. Our study is not only conducive to realize strong magnetoelectric coupling in multiferroics, but also reveals more functionalities in altermagnetic materials. △ Less

Submitted 19 August, 2025; originally announced August 2025.