Materials Science
High-Performance KV$_3$Sb$_5$/WSe$_2$ van der Waals Photodetectors
Yang Yang, Shaofeng Rao, Yuxuan Hou et al. (+7 more)
Kagome metals AV$_3$Sb$_5$ (A = K, Rb, Cs) have recently emerged as a promising platform for exploring correlated and topological
quantum states, yet their potential for optoelectronic applications remains largely unexplored. Here, we report high-performance photodetectors based on van der Waals KV$_3$Sb$_5$/WSe$_2$ heterojunctions. A high-quality Schottky interface readily forms between KV$_3$Sb$_5$ and WSe$_2$, enabling efficient separation and transport of photoinduced carriers. Under 520 nm illumination, the device achieves an open-
circuit voltage up to 0.6 V, a responsivity of 809 mA/W, and a fast response time of 18.3 us. This work demonstrates the promising optoelectronic applications of Kagome metals and highlights the potential of KV$_3$Sb$_5$-based van der Waals
heterostructures for high-performance photodetection.
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All authors Yang Yang, Shaofeng Rao, Yuxuan Hou, Jiabo Liu, Deng Hu, Yufei Guo, Jianzhou Zhao, Hechen Ren, Zhiwei Wang, Fan Yang
Strongly Correlated Electrons · Cross-listed from hep-th
Entropic order parameters and topological holography
Hua-Chen Zhang, Germán Sierra and Javier Molina-Vilaplana
We show that the
symmetry topological field theory (SymTFT) construction, also known as the topological holography, provides a natural and intuitive framework for the entropic order parameter characterising phases with (partially) broken
symmetries. Various examples of group and non-invertible
symmetries are studied. In particular, the origin of the distinguishability of the
vacua resulting from spontaneously broken non-invertible
symmetries is made manifest with an information-theoretic perspective, where certain operators in the SymTFT are excluded from observation.
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Mesoscale and Nanoscale Physics
Non-Euclidean interfaces decode the continuous landscape of graphene-induced surface reconstructions
Li-Qun Shen, Hao-Jin Wang, Mengzhao Sun et al. (+8 more)
Interfacial reconstruction between two-dimensional (2D) materials and metal substrates fundamentally governs
heterostructure properties, yet conventional flat substrates fail to capture the continuous crystallographic landscape. Here, we overcome this topological limitation using non-Euclidean interfaces-curved 2D
graphene-copper surfaces as a model system-to traverse the infinite spectrum of
lattice orientations. By integrating
multimodal microscopy with a deep-learning-enhanced dimensional upscaling framework, we translate 2D scanning electron microscopy (SEM) contrast into quantitative three-dimensional (3D) morphologies with accurate facet identification. Coupling these observations with machine-learning-assisted density functional theory, we demonstrate that reconstruction is governed by a unified thermodynamic mechanism where high-index facets correspond to specific local minima in the surface energy landscape. This work resolves the long-standing complexity of
graphene-copper faceting and establishes non-Euclidean surface
topologies as a generalizable paradigm for decoding and controlling interfacial reconstruction in diverse metal-2D material systems.
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All authors Li-Qun Shen, Hao-Jin Wang, Mengzhao Sun, Yang Xiang, Xin-Ning Tian, Yue Chai, Yue Yang, Feng Ding, Xiao Kong, Marc-Georg Willinger, Zhu-Jun Wang
Materials Science
Increased Covalence and V-center mediated Dark Fenton-Like Reactions in V-doped TiO2: Mechanisms of Enhanced Charge-Transfer
Manju Kumari, Dilip Sasmal, Suresh Chandra Baral et al. (+5 more)
Tuning the valence state and electronic structure of catalytically active sites is crucial for improving Fenton and Fenton-like reactions, which rely on the efficient activation of the H2O2 molecule. Pure TiO2, however, has inadequate activity towards the H2O2 activation and is often constrained by the intrinsic electronic limitations of pristine TiO2. Herein, a rational approach has been demonstrated to improve the Fenton-like catalytic performance of TiO2 through multivalent vanadium (V) doping. A comprehensive characterization using X-Ray Diffraction (XRD), Raman spectroscopy, UV-Vis spectroscopy, X-Ray photoelectron spectroscopy (XPS), Electron paramagnetic resonance (EPR), and Density functional theory (DFT) reveals that V incorporation substantially alters the electronic structure of TiO2. The DFT results, supported by experimental data, indicate that V doping enhances Ti-O covalence and introduces mid-gap states, resulting in a reduced band gap and improved charge transfer. XPS confirms the coexistence of multiple oxidation states of V, which serve as active centres for activating H2O2 and generating OH radicals. As a result, V-doped TiO2 exhibits significantly enhanced dark-catalytic activity in degrading the organic dye Rhodamine B (RhB). Overall, this study provides fundamental insights into multivalent-cation-induced valence state and electronic structure modulation in TiO2, offering a promising strategy for designing high-performance catalysts via defect engineering for sustainable environmental remediation.
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All authors Manju Kumari, Dilip Sasmal, Suresh Chandra Baral, Maneesha P, Poonam Singh, Abdelkrim Mekki, Khalil Harrabi, Somaditya Sen
Materials Science
Extending the Growth Temperature-N Concentration Regime Through Pd Doping in Fe4N Thin Films
Rohit Kumar Meena, Akhil Tayal, Andrei Gloskovskii et al. (+1 more)
Fe4N is a well-known anti-perovskite compound exhibiting high magnetization, high chemical stability, low coercivity, high Curie temperature, and high
spin-polarization ratio. Therefore, it is a viable candidate for applications in spintronic and
magnetic storage devices. However, the Fe4N phase is formed in a narrow substrate temperature (Ts)-N concentration (Nc) regime in the phase diagram of Fe-N. It has been observed that a slight N deficiency will lead to
impurity of alpha-Fe, and some N efficiency would result in epsilon-Fe3N phase. Through this work, it has been demonstrated that the doping of Pd can be suitably utilized to extend the Ts-Nc regime for the growth of Fe4N thin films. EXAFS analysis indicate that Pd atoms are substituting corner Fe atoms. Magnetization measurements reveal that the saturation magnetization reduces nominally with Pd doping up to 13 at.%. Therefore, it is foreseen that Pd doping is effective in extending the Fe4N phase formation regime without a significant impact on its structural, electronic, and
magnetic properties.
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All authors Rohit Kumar Meena, Akhil Tayal, Andrei Gloskovskii, Mukul Gupta
Materials Science
Soft x-rays with Orbital Angular Momentum for resonant scattering experiments at the SOLEIL synchrotron
Pietro Carrara, Franck Fortuna, Renaud Delaunay et al. (+15 more)
The paper presents a comprehensive description of a new setup implemented and commissioned at the SEXTANTS beamline of the SOLEIL synchrotron for absorption and scattering experiments with x-ray beams carrying an orbital angular momentum, also known as twisted x-ray beams. Two alternative methods have been implemented, based on the use of either spiral zone plates or fork gratings devices, and we show how they can be used for both defining and assessing the orbital angular momentum of an x-ray beam. We show also how multiple devices can be used in sequence to define an integer arithmetic of the orbital angular momentum of the final x-ray beam. Finally, we report the results of the first resonant scattering pilot experiments in transmission and reflection mode, intended to assess the feasibility of future users measurements. The availability of twisted soft x-rays complements the range of experimental techniques in elastic, resonant and coherent scattering available at the SEXTANTS beamline of the SOLEIL synchrotron.
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All authors Pietro Carrara, Franck Fortuna, Renaud Delaunay, Joan Vila-Comamala, Benedikt Rösner, Christian David, Stefania Pizzini, Clément Fourniols, Laurent Vila, Matteo Pancaldi, Carlo Spezzani, Flavio Capotondi, Pierre Nonnon, Mauro Fanciulli, Thierry Ruchon, Nicolas Jaouen, Horia Popescu, Maurizio Sacchi
Materials Science
Felix Zahner, Tim Drevelow, Roberto Lo Conte et al. (+3 more)
Topological
spin structures such as
magnetic skyrmions are of fundamental interest and promising for various types of applications in spintronics. Skyrmions have been predicted to emerge also in
antiferromagnetic materials where they exhibit superior transport properties. They were experimentally revealed in synthetic antiferromagnets, however, still remain elusive in intrinsic atomic antiferromagnets. Here, we demonstrate how topological
spin structures can be stabilized in an
antiferromagnetic monolayer. Using
spin-polarized scanning tunneling microscopy, we observe an
antiferromagnetic spin spiral in the Mn monolayer and a collinear
antiferromagnetic state in the Mn double-layer on Ta(110). Near the boundary to the double-layer
spin structures equivalent to half of an
antiferromagnetic skyrmion form in the monolayer as revealed in combination with first-principles calculations and micromagnetic simulations. Our simulations show how the topological state in
antiferromagnetic material systems can be controlled by the configuration within a lateral
heterostructure, resulting in trivial non-coplanar states or
antiferromagnetic skyrmions.
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All authors Felix Zahner, Tim Drevelow, Roberto Lo Conte, Roland Wiesendanger, Stefan Heinze, Kirsten von Bergmann
Other Condensed Matter
High bosonic Bott index and transport of multi-band topological magnons
Kai Tao Huang and X.S Wang
Magnons are bosonic quasiparticles in magnetically ordered systems. Bosonic Bott index has been affirmed as a real-space topological invariant for a two-band
ferromagnetic model. In this work,we theoretically investigate the
topology and transport of
magnons in a multi-band bosonic Kagome
ferromagnetic model. We demonstrate the validity of the bosonic Bott indices of values larger than 1 in multi-band magnonic systems by showing the agreement with Chern numbers in the clean limit and the bulk-boundary correspondence during the topological phase transition. For the high Bott index phase, the disorder-induced topological phase transition occurs in a multi-step manner. Using a generalized Landauer-Buttiker formalism, we reveal how the
magnon transport depends on Gilbert damping and disorder under coherent excitation or temperature difference. The results further justify the bosonic Bott index as a robust real-space topological invariant for multi-band magnonic systems and provide insights into the transport of topological
magnons.
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Materials Science
The effect of germanium sublayer on the native corrosion of ultrathin copper films
Vladimir A. Vdovin and Ivan I. Pyataikin
To examine the process of native corrosion of ultrathin (about 10 nm) copper films deposited on quartz glass substrates $(SiO_2)$ with and without a germanium sublayer, the time dependences of the microwave reflection coefficient $R$ and direct current electrical resistivity $\rho$ of such samples exposed to air at room temperature have been studied. Under these conditions, the thickness of the
oxide layer $d$ on $Cu/SiO_2$ films was found to increase over time $t$ according to a
parabolic law, which is in contradiction with the predictions of existing theories of copper oxidation. A model is proposed that explains this behavior of $d(t)$ by the
diffusion of atomic oxygen along the boundaries of
oxide grains towards the copper film with its subsequent oxidation. The $R$ and $\rho$ of $Cu/Ge/SiO_2$ films were found to degrade much more slowly than similar characteristics of $Cu/SiO_2$ films of the same thickness. The high corrosion resistance of $Cu/Ge/SiO_2$ films is explained by the peculiarities of $Ge$ redistribution during the growth of the copper film on a germanium sublayer. The long-term retention by $Cu/Ge/SiO_2$ films of their characteristics allows them to be recommended as a cheap replacement for gold coating in electromagnetic interference protection devices.
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Quantum Gases · Cross-listed from physics.atom-ph
High-flux cold lithium-6 and rubidium-87 atoms from compact two-dimensional magneto-optical traps
Yun-Xuan Lu, An-Wei Zhu, Christine E. Frank et al. (+2 more)
We report a compact setup with in-series two-dimensional magneto-optical traps (2D MOTs) that provides high-flux cold lithium and rubidium atoms. Thanks to the efficient short-distance Zeeman slowing, the maximum 3D MOT loading rate of lithium atoms reaches a record value of $6.6\times 10^{9}$ atoms/s at a moderate lithium-oven temperature of 372 degrees Celsius, which is 44 times higher than that without the Zeeman slowing light. The flux of rubidium is also as high as $2.3\times10^9$ atoms/s with the rubidium oven held at room temperature. Meanwhile, the entire
vacuum-chamber system, including an ultra-high-
vacuum science
cell, is within a small volume of $55\times65\times70~\mathrm{cm}^3$. Our work represents a substantial improvement over traditional bulky and complex dual-species cold-atom setups. It provides a good starting point for the fast production of a double-degenerate lithium-rubidium atomic mixture and large samples of ultracold lithium-rubidium ground-state molecules.
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All authors Yun-Xuan Lu, An-Wei Zhu, Christine E. Frank, Xin-Yi Huang, Xin-Yu Luo
Soft Condensed Matter · Cross-listed from physics.bio-ph
Mechanical properties of chiral helical polymers-from single filaments to actin bundles
Amir Khosravanizadeh, François Nédélec and Serge Dmitrieff
The mechanical properties of biological
polymers are essential to their biological functions. Here, we introduce a highly coarse-grained model of helical filaments that preserves helicity and chirality while enabling mesoscale simulations. This is implemented in Cytosim, a widely-used open-source cytoskeleton simulation platform. We first show that we can predict the shape and mechanical properties of this helical filament, allowing for its fine control. We find the parameters that allow the resulting filament to accurately match the properties of actin filaments found experimentally}. Using this model of actin, we investigated the role of actin chirality in motor-driven dynamics. We first show that in two different experimental configurations, motor movement along a helical filament results in a
chiral motion of the filament. In a bundle of helical filaments, dimeric motors exert torques on each filament, inducing collective behaviors in the bundle such as rotation, coiling, and helical buckling, reminiscent of those observed in filopodia. Together, these results demonstrate the central role of helicity and chirality in actin mechanics and motor-driven dynamics, and establish our framework as a powerful tool for mesoscale simulations. This framework can also be used for other helical filaments beyond actin.
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Mesoscale and Nanoscale Physics
Linear exciton Hall and Nernst effects in monolayer two-dimensional semiconductors
Weilong Guo, Lianguo Li, Qingjun Tong et al. (+1 more)
This paper focuses on the study of linear
exciton Hall and Nernst effects in monolayer two-dimensional (2D)
semiconductors, employing the semi-classical transport theory. By deriving the
exciton Berry
curvature in momentum space for a general inhomogeneous 2D system, we establish its dependence on the Berry
curvature and the effective mass of electron and hole. As illustrative examples, the
exciton Hall effect in monolayer transition metal dichalcogenides (TMDs) and black phosphorus (BP) are calculated. For these materials, we demonstrate that a linear
Hall (Nernst)
exciton current with the non-zero Berry
curvature is strictly forbidden by the
symmetries. This finding aligns with earlier experimental observations on the
exciton Hall effect in MoSe$_2$. In contrast, a strong anisotropy in BP leads to a net linear
Hall current of
excitons, exhibiting a relatively large value and resembling an anomalous
Hall effect rather than a valley
Hall effect. Our work reveals that the specific
symmetry of 2D materials can induce a significant linear
exciton Hall (Nernst) effect even without Berry
curvature, which is normally forbidden with non-zero Berry
curvature in the monolayer 2D material. This observation holds promise for future optoelectronic applications and offers exciting possibilities for experimental exploration.
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All authors Weilong Guo, Lianguo Li, Qingjun Tong, Ci Li
Mesoscale and Nanoscale Physics · Cross-listed from physics.optics
Photon Echo in Uniaxially Stressed Germanium with Antimony Donors
R.Kh. Zhukavin, V.D. Kukotenko, P.A. Bushuykin et al. (+8 more)
Photon echo is observed in n-type Ge uniaxially stressed along the [111] crystallographic direction, with a coherence relaxation time of 300 ps. The nonlinear polarization responsible for the effect originates from antimony donors. Uniaxial stress induces valley splitting of the donor states, substantially enhancing the coherence time and enabling the observation of
photon echo.
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All authors R.Kh. Zhukavin, V.D. Kukotenko, P.A. Bushuykin, Yu.Yu. Choporova, N.D. Osintseva, K.A. Kovalevsky, V.V. Tsyplenkov, V.V. Gerasimov, N. Dessmann, N.V. Abrosimov, V.N. Shastin
Other Condensed Matter · Cross-listed from quant-ph
Testing Noise Correlations by an AI-Assisted Two-Qubit Quantum Sensor
Dario Fasone, Shreyasi Mukherjee, Mauro Paternostro et al. (+3 more)
We introduce and validate a machine learning-assisted protocol to classify time and space correlations of classical noise acting on a
quantum system, using two interacting
qubits as probe. We consider different classes of noise, according to their Markovianity and spatial correlations. Leveraging the sensitivity of a coherent population transfer protocol under three distinct driving conditions, the various noises are discriminated by only measuring the final transfer efficiencies. This approach reaches around 90% accuracy with a minimal experimental overhead.
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All authors Dario Fasone, Shreyasi Mukherjee, Mauro Paternostro, Elisabetta Paladino, Luigi Giannelli, Giuseppe A. Falci
Disordered Systems and Neural Networks · Cross-listed from physics.soc-ph
The effect of HVDC lines in power-grids via Kuramoto modelling
Kristóf Benedek and Géza Ódor
We present a numerical study on the synchronization and cascade failure behaviour by solving the adaptive second-order Kuramoto model on a large high voltage (HV) European power-grid. This non-perturbative analysis takes into account non-linear effects, which occur even when phase differences are large, when the system is away from the steady state, and even during a blackout cascade. Our dynamical simulations show that improvements in the phase synchronziation stabilization as well as the in the cascade sizes can be related to the finite size scaling behaviour of the second order Kuramoto on graphs with $d_s<4$ spectral dimensions. On the other hand drawbacks in the frequency spread and Braess effects also occur by varying the total transmitted power at large and small global couplings, presumably when the fluctuations are small, causing a freezing in the dynamics. We compare simulations of the fully AC model with those of static or adaptive High Voltage Direct Current (HVDC) line replacements. The adaptive (local frequency difference-based) HVDC lines are more efficient in the steady state, at the expense of very long relaxation times.
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Materials Science
Atomic-scale visualization of d-wave altermagnetism
Daran Fu, Liu Yang, Yi Shen et al. (+7 more)
Altermagnetism is a newly identified
magnetic phase, distinct from conventional ferromagnetism and antiferromagnetism. It exhibits no net magnetization while breaking time-reversal
symmetry. Although its momentum-space signatures are established, direct real-space visualization of its defining rotational-
symmetry breaking remains missing. Here, using scanning tunnelling microscopy, we provide atomic-scale real-space evidence for altermagnetism in CsV2Se2O. Utilizing intrinsic
spin defects as probes, we directly visualize the hallmark
symmetry breaking through unidirectional electronic patterns and elliptical charging rings, both tied to the alternating
spin texture. Moreover, adjacent
spin-defect lines exhibit opposite
spins and long-range
antiferromagnetic coupling, hinting at a novel
spin order. Our work moves the field from momentum-space probes to direct real-space visualization, opening a path to explore how this unconventional
magnetic order couples to other
quantum states.
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All authors Daran Fu, Liu Yang, Yi Shen, Kebin Xiao, Yuyang Wang, Wei Jiang, Zhiwei Wang, Yugui Yao, Qi-Kun Xue, Wei Li
Quantum Gases
Dynamical signatures of superfluidity and shear rigidity in different phases of a dipolar Bose-Einstein condensate
Soumyadeep Halder, Hari Sadhan Ghosh, Axel Pelster et al. (+1 more)
We show that a sudden change in the polarization direction of the
magnetic dipole moments of the atoms in a dipolar Bose-Einstein condensate (BEC) can serve as a useful dynamical probe to sense its superfluid and solid-like properties. We find that for small angular deviation of the polarization direction, actuated for instance by modifying an external
magnetic field, the superfluid state undergoes an undamped scissors mode oscillation, a characteristic signature of superfluidity. In contrast, both the droplet and supersolid states exhibit a scissors-mode oscillation, which is effectively damped due to multiple closely spaced frequency components. Notably, we find that this damping rate provides a qualitative measure for the
rigidity of different phases of a dipolar BEC. Furthermore, there exists a maximum angular deviation of the polarization direction, beyond which the droplet and the supersolid states undergo a permanent deformation i.e., we find an analog of the usual elastic to plastic phase transition of solids. We characterize this transition numerically using the fidelity of the condensate wavefunction with the ground state as well as the droplet width and periodicity of the supersolid density of the condensate which are experimentally accessible. Thus, the dynamical protocol introduced here can be an important experimental
benchmark to identify and characterize the superfluid and solid properties of different phases of dipolar BECs.
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All authors Soumyadeep Halder, Hari Sadhan Ghosh, Axel Pelster, B. Prasanna Venkatesh
Mesoscale and Nanoscale Physics · Cross-listed from physics.optics
Li-Wei Wang, Bolun Hu, Haixiao Zhang et al. (+3 more)
The interplay between
topology and non-Hermiticity gives rise to exotic dynamic phenomena that challenge conventional wave-packet propagation and
entanglement dynamics. While recent studies have established the non-Hermitian skin effect (NHSE) as a key mechanism for anomalous wave dynamics, a unified framework for characterizing and controlling
entanglement evolution in non-Hermitian topological systems remains underdeveloped. Here, by combining theory and experiments, we demonstrate that
entanglement entropy (EE) and transport currents serve as robust dynamic probes to distinguish various non-Hermitian topological regimes. Using a generalized non-Hermitian Su-Schrieffer-Heeger model implemented in an acoustic analog platform, we identify three dynamic phases, bulk-like, edge-like, and skin-like regimes, each exhibiting unique EE signatures and transport characteristics. In particular, skin-like dynamics exhibit periodic information shuttling with finite, oscillatory EE, while edge-like dynamics lead to complete EE suppression. We further map the dynamic phase diagram and show that EE scaling and temporal profiles directly reflect the competition between coherent delocalization and NHSE-driven localization. Our results establish a programmable approach to steering
entanglement and transport via tailored non-Hermitian couplings, offering a pathway for engineering
quantum information dynamics in synthetic phononic, photonic, and
quantum simulators.
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All authors Li-Wei Wang, Bolun Hu, Haixiao Zhang, Kefan Sun, Ying Cheng, Jian-Hua Jiang
Mesoscale and Nanoscale Physics · Cross-listed from physics.optics
Exceptional Points in the Scattering Resonances of a Sphere Dimer
Emanuele Corsaro, Filippo Capolino and Carlo Forestiere
We investigate exceptional points of degeneracy (EPDs) in electromagnetic scattering of a sphere dimer from the electroquasistatic limit to the fully retarded regime. In the quasistatic limit, we prove that $\parity\trev$-symmetric configurations, realized by spheres with complex-conjugate susceptibilities, host EPDs. Beyond this limit, retardation breaks $\mathscr{PT}$-
symmetry; nevertheless, by jointly tuning the material dispersion of the two spheres, we derive analytic synthesis conditions for realizing EPDs at real frequencies. Near an EPD, we show that single-parameter perturbations yield the characteristic square-root splitting of the eigenfrequencies, and we quantify its impact on scattering, extinction, and absorption, clarifying sensing implications.
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Mesoscale and Nanoscale Physics
Chiral dual spin currents field-free perpendicular switching by altermagnet RuO2
Gengchen Meng Qi Sun, Zhicheng Xie, Yumin Yang et al. (+3 more)
Conventional spintronic mechanisms, such as
spin-transfer and
spin-orbit torques based on the
spin current, rely on breaking time-reversal
symmetry to manipulate
magnetic moments. In contrast, for spatially separated dual
spin currents, the time-reversal-invariant vector chirality emerges as a critical factor governing magnetization dynamics. Here, we investigate field-free perpendicular magnetization switching in an altermagnet RuO2/ferromagnet/heavy metal Pt trilayer, driven by
chiral dual
spin currents (CDSC). We demonstrate that the chirality of these dual
spin currents acts as the deterministic role in breaking out-of-plane
symmetry. Leveraging the intrinsic
spin-splitting effect of the d-wave altermagnet to generate an x-polarized
spin component, the interplay of non-collinear
spin currents from two adjacent layers induces a helical
magnetic texture within the intermediate layer. The resulting intralayer exchange coupling manifests as an effective in-plane
magnetic field, facilitating deterministic switching. This distinct physical picture, validated by switching measurements and micromagnetic simulations, reveals that the switching polarity is dictated by chirality rather than charge current polarity. Characterized by the novel
symmetry and low power consumption, CDSC offers a promising paradigm for next-generation high-performance spintronic architectures.
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All authors Gengchen Meng Qi Sun, Zhicheng Xie, Yumin Yang, Yu Zhang, Na Lei, Dahai Wei
Materials Science
Tunable Carrier Dynamics in Carbide Antiperovskites via A-Site Cation Substitution
Sanchi Monga and Saswata Bhattacharya
We present a comprehensive first-principles investigation of the electronic structure and excited-state carrier dynamics in the carbide antiperovskites Ca$_6$CSe$_4$ and Sr$_6$CSe$_4$. Using many-body perturbation theory ($G_0W_0$/BSE), we show that both materials are direct band gap
semiconductors with quasiparticle gaps of 1.66 eV (Ca) and 1.22 eV (Sr), lying in the visible-near-infrared range, and exhibit moderate excitonic binding energies. Ab initio nonadiabatic molecular dynamics simulations at 300 K reveal distinct relaxation mechanisms governed by the interplay of band gap, nonadiabatic (NA) couplings, and electronic decoherence. In Ca$_6$CSe$_4$, stronger
lattice fluctuations induce 38% larger band gap variations and 28% faster decoherence, which, together with approximately 53% weaker NA couplings, suppress nonradiative recombination and yield lifetimes nearly 18 times longer (40.3 ns) than in Sr$_6$CSe$_4$ (2.2 ns). Hot-carrier cooling in both systems occurs on picosecond timescales (1-9 ps) with a pronounced slow down near the band egdes. Overall, our results demonstrate that A-site cation substitution provides an effective route to control carrier lifetimes and relaxation pathways in antiperovskites, offering microscopic insight into
lattice-driven carrier dynamics and guiding their experimental realization and optimization.
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Materials Science
Thermal Evolution of Skyrmions in Synthetic Ferrimagnets of Co/Gd Heterostructure for Topological Spintronic Applications
Bhuvneshwari Sharma, Soumyaranjan Dash, Shaktiranjan Mohanty et al. (+5 more)
Synthetic ferrimagnetic (SFiM) multilayers offer a versatile platform for hosting skyrmions with tunable
magnetic properties, combining the advantages of ferromagnets and antiferromagnets. Unlike synthetic antiferromagnets, SFiMs retain a finite magnetization that allows direct observation of
magnetic textures while still benefiting from reduced dipolar fields and a suppressed skyrmion
Hall effect. However, a systematic investigation of their temperature and field dependent magnetization
evolution, including the labyrinthine-to-skyrmion transition in Co/Gd-based SFiMs, remains less explored. Here, we demonstrate the stabilization of 70 nm-radius skyrmions at room temperature and reveal how the Co and Gd sublattices influence the temperature-dependent net magnetization. Further, we develop a microscopic
spin model for SFiM incorporating the relevant
magnetic interactions, which reproduces the experimental observations and captures the temperature-dependent
magnetic phase
evolution. This framework highlights the interplay of fundamental interactions controlling skyrmion stability in SFiM and provides a pathway for engineering
heterostructures for topological spintronic applications.
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All authors Bhuvneshwari Sharma, Soumyaranjan Dash, Shaktiranjan Mohanty, Brindaban Ojha, Debi Rianto, Del Atkinson, Sanjeev Kumar, Subhankar Bedanta
Strongly Correlated Electrons
Exactly Solvable Models Hosting Altermagnetic Quantum Spin Liquids
João Augusto Sobral, Pietro M. Bonetti, Subrata Mandal et al. (+1 more)
We construct
spin-$3/2$ and
spin-$7/2$ models on the square-octagon and checkerboard
lattices that are exactly solvable with Majorana representations. They give rise to
spin-
liquid phases with full
spin-rotation and
lattice-translational
symmetries but broken time-reversal
symmetry. Although non-zero on elementary plaquettes, the net orbital
magnetic moment is guaranteed to vanish as a result of point
symmetries; due to the analogy to long-range ordered altermagnets, these types of phases were dubbed altermagnetic
spin liquids in [Phys. Rev. Research 7, 023152 (2025)]. For the
spin-$3/2$ model, we find that a $g$-wave altermagnetic
spin liquid emerges as the unique ground state. In contrast, the
spin-7/2 model exhibits a significantly richer phase diagram, involving different types of
chiral spin liquids competing with a $d$-wave altermagnetic
spin liquid. Finally, we identify and characterize the topological and non-topological excitations, illustrating the rich physics of altermagnetic
spin liquids resulting from the interplay of non-trivial topological and
symmetry aspects of this novel phase of matter.
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All authors João Augusto Sobral, Pietro M. Bonetti, Subrata Mandal, Mathias S. Scheurer
Strongly Correlated Electrons
Skyrmion and Meron Crystals in Intermetallic Gd$_3$Ru$_4$Al$_{12}$: Microscopic Model Insights into Chiral Phases
Jiajun Mo, Leandro M. Chinellato, Fletcher Williams et al. (+14 more)
Topological
spin textures in frustrated intermetallics hold great promise for spintronics applications. However, understanding their origin and properties remains a significant challenge due to competing and often long-range interactions mediated by conduction electrons. Here, by combining
neutron scattering experiments with theoretical modeling via unprecedented multi-target fits that further incorporate the ferromagnentic resonance data and magnetization curve, we construct a realistic microscopic model for the prototypical intermetallic skyrmion host \text{Gd}$_3$\text{Ru}$_4$\text{Al}$_{12}$. Beyond
magnetic frustration, we identify the competition between dipolar interactions and easy-plane single-ion anisotropy as a key ingredient for stabilizing the rich
chiral magnetic phases observed in this compound – including a hexagonal skyrmion
crystal and two distinct meron
crystals. Remarkably, the meron
crystal in lower field is revealed to be commensurate with the underlying
lattice, and its unique three-meron-one-antimeron
spin texture is verified by the polarized x-ray diffraction data. At elevated temperatures, the short-range
spin correlations in \text{Gd}$_3$\text{Ru}$_4$\text{Al}$_{12}$ are well described by a codimension-two spiral
spin-
liquid. Perturbations from staggered Dzyaloshinskii-Moriya interactions give rise to
chiral fluctuations that account for the temperature and field dependence of the anomalous
Hall response. Our results highlight the unique power of
neutron scattering, especially when combined with complementary experimental techniques, to unravel complex
magnetic phase transitions and provide new insights into the rich variety of topological
spin textures in frustrated systems.
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All authors Jiajun Mo, Leandro M. Chinellato, Fletcher Williams, Akiko Kikkawa, Joseph A. M. Paddison, Matthias D. Frontzek, Gabriele Sala, Chris Pasco, Kipton Barros, Taro Nakajima, Taka-hisa Arima, Yasujiro Taguchi, Yoshinori Tokura, Matthew B. Stone, Andrew D. Christianson, Cristian D. Batista, Shang Gao
Mesoscale and Nanoscale Physics
Diffusive metal in a percolating Chern insulator
Subrata Pachhal, Naba P. Nayak, Soumya Bera et al. (+1 more)
Two-dimensional non-interacting
fermions without any anti-
unitary symmetries generically get Anderson localized in the presence of disorder. In contrast, topological
superconductors with their inherent particle-hole
symmetry can host a thermal metallic phase, which is non-universal and depends on the nature of microscopic disorder. In this work, we demonstrate that in the presence of
geometric disorders, such as random bond dilution, a robust metal can emerge in a Chern
insulator with particle-hole
symmetry. The metallic phase is realized when the broken links are weakly stitched via concomitant insertion of $\pi$ fluxes in the plaquettes. These nucleate low-energy
manifolds, which can provide percolating conduction pathways for
fermions to elude localization. This diffusive metal, unlike those in
superconductors, can carry charge current and even anomalous
Hall current. We investigate the transport properties and show that while the topological
insulator to Anderson
insulator transition exhibits the expected Dirac universality, the metal
insulator transition displays a different critical exponent $\nu \approx 2$ compared to a disordered topological
superconductor, where $\nu \approx 1.4$. Our work emphasizes the unique role of
geometric disorder in engineering novel phases and their transitions in topological
quantum matter.
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All authors Subrata Pachhal, Naba P. Nayak, Soumya Bera, Adhip Agarwala
Statistical Mechanics · Cross-listed from math-ph
Quantum two-dimensional superintegrable systems in flat space: exact-solvability, hidden algebra, polynomial algebra of integrals
Alexander V Turbiner, Juan Carlos Lopez Vieyra and Pavel Winternitz
In this short review paper the detailed analysis of six two-dimensional
quantum superintegrable systems in flat space is presented. It includes the Smorodinsky-Winternitz potentials I-II (the Holt potential), the Fokas-Lagerstrom model, the 3-body Calogero and Wolfes (equivalently, $G_2$ rational, or $I_6$) models, and the Tremblay-Turbiner-Winternitz (TTW) system with integer index $k$. It is shown that all of them are exactly-solvable, thus, confirming the Montreal
conjecture (2001); they admit algebraic forms for the
Hamiltonian and both integrals (all three can be written as differential operators with
polynomial coefficients without a constant term), they have
polynomial eigenfunctions with the invariants of the discrete
symmetry group of invariance taken as variables, they have hidden (Lie) algebraic structure $g^{(k)}$ with various $k$, and they possess a (finite order)
polynomial algebras of integrals. Each model is characterized by infinitely-many finite-dimensional invariant subspaces, which form the infinite flag. Each subspace coincides with the finite-dimensional representation space of the
algebra $g^{(k)}$ for a certain $k$. In all presented cases the
algebra of integrals is a 4-generated $(H, I_1, I_2, I_{12}\equiv[I_1, I_2])$ infinite-dimensional
algebra of ordered monomials of degrees 2,3,4,5, which is a subalgebra of the universal enveloping
algebra of the hidden
algebra.
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Mesoscale and Nanoscale Physics
Heavy-Tailed Hall Conductivity Fluctuations in Quantum Hall Transitions
Emuna Rimon, Eytan Grosfeld and Yevgeny Bar Lev
We study the full distribution of the zero-temperature
Hall conductivity in a
lattice model of the IQHE using the Kubo formula across disorder realizations. Near the localization-delocalization transition, the conductivity exhibits heavy-tailed fluctuations characterized by a power-law decay with exponent $\alpha \approx 2.3$–$2.5$, indicating a finite mean but a divergent variance. The heavy tail persists across a range of system sizes, correlation lengths of the disorder potential and fillings. Our results demonstrate a breakdown of self-averaging in transport in small, coherent samples near criticality, in agreement with findings in random
matrix models of topological indices.
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Materials Science
Selective Amplification of the Topological Hall Signal in Cr$_2$Te$_3$: The Role of Molecular Exchange Coupling
Suman Mundlia, Ritesh Kumar, Anshika Mishra et al. (+3 more)
Layered
magnetic transition-metal chalcogenides (TMCs) are a focal point of research, revealing a variety of intriguing
magnetic and topological ground states. Within this family of TMCs, chromium telluride has garnered significant
attention because of its excellent tunability in
magnetic response, owing to the presence of competing
magnetic exchange interactions. We here demonstrate the manipulation of
magnetic anisotropy in ultra-thin Cr$_2$Te$_3$ films through growth engineering leading to a controlled transition from in-plane to out-of-plane orientation with an intermediate non-coplanar
magnetic ground phase characterized by a topological
Hall effect. Moreover, interfacing these films with Vanadyl phthalocyanine (VOPc) molecules prominently enhances the non-coplanar
magnetic phase, attributing its presence to the competing interfacial
magnetic exchange interactions over the
spin-orbit-driven interfacial effects. These findings pave the way for the realization of novel topological spintronic devices through interface-modulated exchange coupling.
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All authors Suman Mundlia, Ritesh Kumar, Anshika Mishra, Malavika Chandrasekhar, Narayan Mohanta, Karthik V. Raman
Materials Science
Bayesian inference and uncertainty quantification for modeling of body-centered-cubic single crystals
Seunghyeon Lee, Thao Nguyen, Darby J. Luscher et al. (+3 more)
Uncertainties in the high-dimensional space of material parameters pose challenges for the predictive modeling of bcc single
crystals, especially under extreme loading conditions. In this work, we identify the key physical assumptions and associated uncertainties in constitutive models that describe the deformation behavior of bcc single
crystal molybdenum subjected to quasi-static to shock loading conditions. We employ two representative physics-based bcc single
crystal plasticity models taken from our previous work (Nguyen et al. 2021a; Lee et al. 2023b), each prioritizing different key deformation mechanisms. The
Bayesian model calibration (BMC) is used for probabilistic estimates of material parameters in both bcc
crystal plasticity models. In conjunction with the BMC procedure, the global sensitivity analysis is conducted to quantify the impact of uncertainties in the material parameters on the key simulation results of quasi-static to shock responses. The sensitivity indices at various loading conditions clearly illustrate the physical basis underlying the predictive capabilities of the two distinct bcc
crystal plasticity models at low to high strain rates. Both of the calibrated bcc models are then further validated beyond the calibration regime, by which we further identify critical physical mechanisms that govern the transient elastic-plastic responses of single
crystal molybdenum under shock loading. The statistical inference framework demonstrated here facilitates the further development of continuum
crystal plasticity models that account for a broad range of deformation mechanisms.
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All authors Seunghyeon Lee, Thao Nguyen, Darby J. Luscher, Saryu J. Fensin, John S. Carpenter, Hansohl Cho
Strongly Correlated Electrons · Cross-listed from hep-th
On the Absence of Symmetric Simple Conformal Boundary Conditions
Pengcheng Wei and Yunqin Zheng
Non-trivial 't Hooft anomaly obstructs the existence of a simple symmetric conformal boundary condition in a CFT. Conversely, there is a common piece of lore that trivial 't Hooft anomaly promises the existence of a simple
symmetry conformal boundary condition in a given CFT. Recently, counter examples to this lore was realized in tetracritical Ising CFT [1] and compact
boson [2] – the simple conformal boundary conditions preserving certain anomaly-free subsymmetry are absent in these CFTs. In this work, we uncover the underlying reason for the absence of these boundary conditions in counter examples, and propose a criterion diagnosing when the lore fails for any given 2d CFT. The
Symmetry TFT description for boundary conditions plays a crucial role.
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