Strongly Correlated Electrons
Coupled Majorana modes in a dual vortex of the Kitaev honeycomb model
Surajit Basak and Jean-Noël Fuchs
The Kitaev model is exactly solvable in terms of Majorana
fermions hopping on a honeycomb
lattice and coupled to a static $\mathbb{Z}_2$ gauge field, giving the possibility of $\pi$-
vortices in hexagonal plaquettes. In the
vortex-full sector and in the presence of a time-reversal-breaking three-
spin term of strength $\kappa$, the energy spectrum is gapped and the ground state possesses an even Chern number. An isolated
vortex-free plaquette acts as a “dual
vortex” and binds a fermionic mode at finite energy $\epsilon$ in the bulk gap. This mode is equivalent to two coupled Majorana zero modes located on the same dual
vortex. In a continuum approximation, we analytically compute the Majorana wavefunctions and their coupling $\epsilon$ in the two limits of small or large $\kappa$. The analytical approach is confirmed by numerical perturbation theory directly on the
lattice. The latter is in excellent agreement with the full numerics on a finite-size system. We contrast our results with states bound to an isolated
vortex in a topological
superconductor with even Chern number.
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Materials Science
2D abrupt nano-junctions blending sp-sp2 bonds on atomically precise heterostructures
Alice Cartoceti, Simona Achilli, Masoumeh Alihosseini et al. (+8 more)
Two-dimensional
heterostructures combining sp-sp2 hybridization,blending
graphene with graphyne-based allotropes, offer substantial potential for enhancing the tunability of electronic and transport properties while providing significant structural flexibility. These attributes are desirable for next generation nanoscale electronic applications. Despite such potential, their experimental realization remains elusive, as synthesized carbon
heterostructures are limited to doped,
graphene-based systems exhibiting exclusively sp2 hybridization. Here, we demonstrate the on-surface synthesis of covalently bonded sp-sp2 lateral
heterostructures between
graphene nanoribbons and graphdiyne networks on Au(111). Atomic-resolution scanning tunnelling microscopy, combined with density functional theory, reveals the formation mechanism of the covalent interfacial bonds between nanoribbons and graphdiynes, also highlighting the key role of surface chemistry. Bromine atoms deriving from the molecules dehalogenation and chemisorbed along the nanoribbon inhibit the junction formation, but bonding efficiency can be boosted up to 71% by controlled removal of these by-products. Electronic structure and transport calculations show that the 2D
heterostructure by itself is characterized by disentangled properties for the two subsystems, forming an atomically narrow junction enabling voltage-tunable spatial current separation in two dimensions. There results define a viable strategy for engineering
graphene-based sp-sp2
heterostructures, paving the way for the design and synthesis of all-carbon nanoscale electronic architectures.
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All authors Alice Cartoceti, Simona Achilli, Masoumeh Alihosseini, Adriana E. Candia, Enrico Beltrami, Paolo D'Agosta, Alessio Orbelli Biroli, Francesco Sedona, Andrea Li Bassi, Jorge Lobo Checa, Carlo S. Casari
Materials Science
Charge redistribution at metal-ZrO2 interfaces: A combined DFT and continuum electrostatic study
Ximeng Wang, Yongfeng Zhang, Dmitry Skachkov et al. (+5 more)
Nanoscale metallic inclusions (NMIs) are commonly observed within
oxide scales formed during high-temperature oxidation, revealing the existence of chemical and electronic heterogeneity beyond conventional corrosion theories that assume homogeneous, fully oxidized films. Using tetragonal zirconia (tZrO2) facing a series of face-centered cubic (fcc) metals as the model system, this work investigates the short-range and long-range charge redistributions across metal-
oxide interfaces by coupling density functional theory (DFT) calculations with continuum modeling. We show that metal-
oxide contact induces a short-range charge redistribution confined to a few atomic layers and a long-range redistribution of space charge that can extend over macroscopic distances within weakly doped
oxides. DFT calculations show that the short-range redistribution is dominated by metal induced gap states (MIGS) in tZrO2 facing noble metals like Au and Ag, and by chemical bonding in tZrO2 facing active metals like Al. DFT-informed continuum theoretical analysis shows that the range of space-charge redistribution is governed by the doping level of tZrO2, and that the Schottky barrier height (SBH) exhibits a stronger dependence on the metal work function than the doping level. Both the short-range and long-range charge redistributions can alter the transport of charge carriers via their associated electric fields, extending several nm to hundreds of nm from the interface, depending on the doping concentrations, suggesting possible heterogeneous
oxide growth caused by NMIs.
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All authors Ximeng Wang, Yongfeng Zhang, Dmitry Skachkov, Arnab Das, Junliang Liu, Alexander Kvit, Jennifer T. Choy, Adrien Couet
Soft Condensed Matter
Emergent hydrodynamics of chiral active fluids: vortices, bubbles and odd diffusion
Umberto Marini Bettolo Marconi, Alessandro Petrini, Raphaël Maire et al. (+1 more)
Starting from a microscopic multiparticle Langevin equation, we systematically derive a hydrodynamic description in terms of density and momentum fields for
chiral active particles interacting via standard repulsive and nonlocal odd forces. These odd interactions are reciprocal but non-conservative: they are non-potential forces, as they act perpendicular to the vector joining any pair of particles. As a result, the torques that two particles exert on one another are non-reciprocal. The ensuing macroscopic continuum description consists of a continuity equation for the density and a generalized compressible Navier-Stokes equation for the fluid velocity. The latter includes a chirality-induced torque density term and an odd viscosity contribution. Our theory predicts the emergence of odd diffusivity, edge currents, and an inhomogeneous phase - characterized by bubble-like structures - recently observed in simulations. Specifically, the theory exhibits a linear instability arising from the interplay between odd viscosity and torque density, and admits steady-state inhomogeneous solutions featuring bubbles and
vortices, in agreement with numerical simulations. Our findings can be tested experimentally in systems of granular spinners or rotating microorganisms suspended in a fluid.
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All authors Umberto Marini Bettolo Marconi, Alessandro Petrini, Raphaël Maire, Lorenzo Caprini
Materials Science
Mapping optical, chemical, structural features in ZrO2 via cross-sectional SEM-Cathodoluminescence correlation microscopy
Ricardo Vidrio, Yuhan Tong, Junliang Liu et al. (+11 more)
Understanding how nanoscale heterogeneities influence charge transport and mass transfer in
oxides is critical for developing advanced materials for energy and electronic uses. In high-temperature applications, the formation of thermal
oxides with complex chemical and structural features plays a central role in material lifetime. While thermally grown zirconia (ZrO2) on zirconium
alloys exhibits strong chemical and microstructural gradients across the
oxide thickness, linking these heterogeneities to electronic-defect landscapes remains challenging. We demonstrate cross-sectional scanning electron microscope-cathodoluminescence (SEM-CL) as a mesoscale probe of spatial variations in luminescence in zirconia and establish correlations with co-registered electron backscatter diffraction (EBSD) and electron probe micro-analysis (EPMA) on the same region. The SEM-CL signal is dominated by the ~2.7 eV defect band, but its intensity varies strongly across the
oxide cross section. Correlative EBSD-CL analysis reveals that CL intensity increases with grain area and decreases at the grain boundaries, consistent with enhanced non-radiative recombination associated with microstructural disorder. EPMA mapping shows that a substantial fraction of CL-dark features co-localize with secondary phase precipitates enriched in iron. These results show that SEM-CL contrast in corrosion-grown ZrO2 is controlled by both chemical heterogeneity and microstructural disorder, underscoring the need for correlative registration to interpret CL images. This multi-modal approach provides an efficient route to connect electronic properties and luminescence signatures across complex
oxide cross sections to underlying chemistry and microstructure, thereby providing a pathway to relate local defect landscapes to regions likely to bias electronic/ionic transport during oxidation.
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All authors Ricardo Vidrio, Yuhan Tong, Junliang Liu, Bil Schneider, William O. Nachlas, Nathan Curtis, Maryam Zahedian, Alexander Kvit, Hongliang Zhang, Zefeng Yu, Ximeng Wang, Yongfeng Zhang, Adrien Couet, Jennifer T. Choy
Mesoscale and Nanoscale Physics · Cross-listed from physics.optics
Engineering Photoluminescence with Mie Voids
Yuchao Fu, Ilia Lykov, Sergejs Boroviks et al. (+5 more)
Spontaneous emission, as a fundamental radiative process and a versatile information carrier, plays a vital role in light-emitting devices, optical information modulation and encryption, super-resolution fluorescence imaging. Engineering the photonic environment surrounding
photon emitters enables control over their emission properties. However, simultaneously achieving precise engineering of both excitation enhancement and
quantum-yield modulation at the nanoscale remains elusive, highlighting substantial room for advancing the precise orchestrating of photoluminescence. Here, we introduce silicon Mie voids - air-defined cavities that invert the conventional solid-particle geometry - to achieve independent tuning of photoluminescence within a single subwavelength unit, while minimizing optical losses. Full-wave simulations and experiments on both gradient and uniform Mie-void arrays jointly validate this quantitative framework for spontaneous emission tuning, which disentangles excitation enhancement arising from local field confinement in air and
quantum-yield enhancement resulting from strengthened emitter-resonator coupling, while confirming the accelerated radiative decay enabled by the modified optical LDOS. Leveraging this flexible mechanism, we realize a
multimodal nanophotonic pattern with near-diffraction-limited pixels that encode the EPFL logo in the bright field and the SJTU logo in both dark field and photoluminescence maps. These results establish Mie voids as a powerful platform for high-density
multimodal encrypted displays and open new avenues for advancing state-of-the-art nanophotonic devices.
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All authors Yuchao Fu, Ilia Lykov, Sergejs Boroviks, Nai-Quan Zhu, Tianyue Li, Siarhei Zavatski, Makhlad Chahid, Olivier J. F. Martin
Quantum Gases · Cross-listed from nucl-th
Short-distance production of three particles with large scattering length
Timothy G. Backert, Sebastian Dietz, Hans-Werner Hammer et al. (+2 more)
The short-distance production of multi-particle states in high-energy
nuclear reactions provides a unique way to study the low-energy properties of few-body systems. In particular, the production amplitude of multineutron systems is strongly constrained by an approximate conformal
symmetry of the underlying theory. We calculate the full amplitude for the short-distance production of three particles with large scattering length in leading order pionless EFT, focusing on the cases of three
neutrons and three spinless
bosons. We investigate the signature of low-energy resonances and other correlations in the relative energy distributions. For the case of
neutrons, we compare to the predictions from approximate conformal
symmetry close to the
unitary limit and calculate the range corrections up to next-to-next-to leading order.
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All authors Timothy G. Backert, Sebastian Dietz, Hans-Werner Hammer, Sebastian König, Dam Thanh Son
Mesoscale and Nanoscale Physics
Deterministic non-local parity control and supercurrent-based detection in an Andreev molecule
Shang Zhu, Xiaozhou Yang, Mingli Liu et al. (+15 more)
The ability to manipulate and detect the parity of
quantum states in
superconductor-
semiconductor hybrid systems is pivotal to realizing the promise of topological
quantum computation. However, as these architectures scale toward artificial Kitaev chains with phase-control loops, local accessibility becomes restricted, constraining conventional local parity control and detection. While Andreev molecules offer a platform for non-local intervention, deterministic protocols for parity manipulation have yet to be experimentally established. Here, we demonstrate deterministic non-local control over the parity configuration of a
quantum dot (QD) by electrically modulating the coherent hybridization with a spatially adjacent QD within an Andreev molecule. By systematically investigating three distinct joint parity configuration regimes in the elastic co-tunneling limit, we experimentally uncover the operational conditions for this non-local control. In conjunction with theoretical simulations establishing a global phase diagram, we identify a set of universal selection rules governing parity transitions, dictated by the
symmetry-imposed interplay between the joint parity configuration and the dominant inter-dot coupling mechanism (elastic co-tunneling vs. crossed Andreev reflection). Furthermore, we establish the supercurrent, directly signaled by zero-bias conductance peaks, as an intrinsic, sensor-free probe of the parity configuration, obviating the need for auxiliary charge sensors. Our results provide a validated physical framework for parity engineering, offering a key building block for scalable, multi-QD superconducting architectures.
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All authors Shang Zhu, Xiaozhou Yang, Mingli Liu, Min Wei, Yiping Jiao, Jiezhong He, Bingbing Tong, Junya Feng, Ziwei Dou, Peiling Li, Jie Shen, Xiaohui Song, Guangtong Liu, Zhaozheng Lyu, Dong Pan, Jianhua Zhao, Li Lu, Fanming Qu
Mesoscale and Nanoscale Physics
Molecular Hamiltonian learning from setpoint-dependent scanning tunneling spectroscopy
Greta Lupi, Adolfo O. Fumega, Mohammad Amini et al. (+3 more)
Molecular
quantum magnets adsorbed on surfaces exhibit rich
spin and orbital excitations that can be probed by scanning tunneling microscopy with inelastic electron tunneling spectroscopy (STM-IETS). However, the quantitative extraction of the underlying multiorbital
Hamiltonian from experimental spectra remains a fundamental challenge. Here, we introduce molecular
Hamiltonian learning, a machine learning strategy that infers the microscopic
Hamiltonian parameters of a single adsorbed molecule directly from the setpoint-dependence of STM-IETS data. The method leverages the systematic
evolution of spectral features as the STM tip tunes the local electrostatic environment for different tip-sample distances. We demonstrate this approach on iron phthalocyanine on ferroelectric SnTe, training our
algorithm on theory spectra from a realistic multiorbital model, including
spin-orbit coupling, electrostatic interactions, local
crystal field, and substrate effects. The
algorithm, trained solely on theoretical many-body simulations, allows reconstructing
Hamiltonian parameters directly from experimental spectra. Our manuscript establishes a flexible and automated strategy for
Hamiltonian reconstruction from STM-IETS, transforming setpoint-dependent spectroscopy into quantitative characterization of
quantum materials at the atomic scale.
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All authors Greta Lupi, Adolfo O. Fumega, Mohammad Amini, Robert Drost, Peter Liljeroth, Jose L. Lado
Strongly Correlated Electrons
Probing multipolar order in the candidate altermagnet MnF$_2$ through the elastocaloric effect under strain
Rahel Ohlendorf, Luca Buiarelli, Hilary M. L. Noad et al. (+5 more)
Altermagnets break a combination of time-reversal and rotational
symmetries without generating a net magnetization. As such, the order parameter of $d$-wave altermagnets has the same
symmetry as
magnetic multipoles, and couples to the product of a
magnetic field and uniaxial strain. We combine elastocaloric experiments, free-energy modeling, and first-principles calculations on MnF$_2$ to establish a thermodynamic probe of the predicted finite-temperature altermagnetic critical point. These results pave the way to explore altermagnetic
quantum criticality in $d$-wave materials and beyond.
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All authors Rahel Ohlendorf, Luca Buiarelli, Hilary M. L. Noad, Andrew P. Mackenzie, Rafael M. Fernandes, Turan Birol, Jörg Schmalian, Elena Gati
Soft Condensed Matter
On the Determination of Gel Points
Kazumi Suematsu, Haruo Ogura, Seiichi Inayama et al. (+1 more)
A critical composition of cross-linked polysiloxanes observed by Scanlan and Winter is reinvestigated in comparison with the theory of gelation. We assume, based on the Scott findings, the
geometric distribution for one of the monomers, divinyl-terminated poly(dimethylsiloxane). Calculation results show that the two theories are in near-consistency, supporting the Scanlan-Winter estimation based on the linear viscoelastic theory. On the other hand, there is a disturbing result that calculation using the mean molecular weight, $M_{n}$, leads to exact agreement between the two theories, suggesting that the distribution is in effect monodisperse, contrary to the assumed
geometric one and also the observed polydispersity, $M_w/M_n=2.1$. Further experimental studies employing monodisperse monomers would be highly valuable to consolidate the bridge between these two fundamental theories.
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All authors Kazumi Suematsu, Haruo Ogura, Seiichi Inayama, Toshihiko Okamoto
Mesoscale and Nanoscale Physics
Ultrastrong light-matter coupling in near-field coupled split-ring resonators revealed by photocurrent spectroscopy
Jing Huang, Jinkwan Kwoen, Yasuhiko Arakawa et al. (+2 more)
Landau polaritons arising from the coupling between cyclotron resonance and terahertz split-ring resonators (SRRs) have served as a central platform for exploring ultrastrong light-matter interaction for more than a decade. Over this period, a wide variety of SRR architectures, differing in size, geometry, and even material composition, have been investigated. However, the regime of near-field coupled SRRs has remained largely unexplored. Here, we demonstrate ultrastrong coupling using photocurrent spectroscopy in two prototypical near-field configurations: a SRR dimer and a topological SRR chain. The measurements reveal hybridization not only with bright resonant modes but also with optically dark modes and topological edge modes, highlighting the exceptional sensitivity of the photocurrent spectroscopy. Moreover, the engineered near-field interactions allow the study of multi-mode ultrastrong coupling and the interplay between topological band structure and cavity
quantum electrodynamics.
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All authors Jing Huang, Jinkwan Kwoen, Yasuhiko Arakawa, Kazuhiko Hirakawa, Kazuyuki Kuroyama
Materials Science
Symmetry Adapted Analysis of Screw Dislocation: Electronic Structure and Carrier Recombination Mechanisms in GaN
Yuncheng Xie, Haozhe Shi, Menglin Huang et al. (+3 more)
As fundamental one-dimensional defects, screw dislocations profoundly reshape the energy landscape and carrier dynamics of crystalline materials. By restoring the exact
algebra of the screw dislocation group, we unveil the latent
symmetry constraints that govern the electronic structure, providing a more rigorous physical picture than the conventional treatments. When applied to GaN, the method yields a band-connectivity constraint and rigorous dipole selection rules for polarization-resolved transitions. Combined with computed
Hamiltonian matrix, the approach gives
symmetry-filtered radiative and dielectric calculations and reveals a piezoelectrical effect at the dislocation core that strongly suppresses radiative recombination. The pronounced dominance of non-radiative capture over radiative recombination highlights the detrimental impact of screw dislocations on the luminous efficiency of GaN, providing a theoretical foundation for optimizing dislocation-limited optoelectronic devices.
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All authors Yuncheng Xie, Haozhe Shi, Menglin Huang, Weibin Chu, Shiyou Chen, Xin-Gao Gong
Superconductivity
AC Response Across the Metal Insulator Transition of YBCO Josephson Junctions Fabricated with a Helium Ion Beam
Adhilsha Parachikunnumal, Nirjhar Sarkar, Aravind Rajeev Sreeja et al. (+5 more)
Using focused helium ion beam (FHIB) irradiation, we fabricated in-plane, high-Tc YBCO Josephson junctions. By varying the dose of the irradiation, we tune the junction barriers from metallic (SNS) to insulating (SIS) and investigate how this transition affects microwave-driven dynamics. As the barrier transitions from metallic to insulating, the oscillatory response of the Shapiro steps to the RF power changes dramatically. On either side of the metal-
insulator transition, the devices exhibit clean integer Shapiro steps without half-integer features, demonstrating that the current–phase relation is dominated by the first harmonic and that the excess current is minimal. The current-voltage response is well-described by the resistively, capacitively shunted junction model assuming a single-harmonic current–phase relation. This behavior indicates well-controlled junction properties suitable for a wide range of superconducting electronics, including detectors, mixers, and high-density integrated
circuits.
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All authors Adhilsha Parachikunnumal, Nirjhar Sarkar, Aravind Rajeev Sreeja, Sreekar Vattipalli, Rochelle Qu, Jay C. LeFebvre, Roger K. Lake, Shane A. Cybart
Materials Science
Site preference of chalcogen atoms in 1T$^\prime$ $MX_{2(1-x)}Y_{2x}$ ($M=$ Mo and W; $X, Y=$ S, Se, and Te)
Shota Ono and Ryotaro Ohse
The
insulator-metal transition, accompanying the structural phase transition from 2H to 1T$^\prime$ structure, has been reported in two-dimensional W-S-Te and W-Se-Te systems. It is also reported that Te atoms tend to occupy a specific site of the 1T$^\prime$ structure. Here, we study the site preference of chalcogen atoms in $MX_{2(1-x)}Y_{2x}$ ($M=$ Mo and W; $X, Y=$ S, Se, and Te; $0\le x \le 1$) using first-principles approach. We demonstrate that the site preference of chalcogen atoms explains the universal correlation between the formation energy and the Peierls-like distortion amplitude in the 1T$^\prime$ phase. The impact of the site preference on the linear elastic properties is strong, whereas its impact is weak in the non-linear regime. This establishes the structure-property relationships in $MX_{2(1-x)}Y_{2x}$ systems.
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Statistical Mechanics
Evidence of the de Almeida-Thouless transition in three-dimensional spin glasses
L. H. Miranda-Filho and Yuliang Jin
The nature of
spin-glass states in a
magnetic field remains a major open problem in statistical physics. The existence of the de Almeida-Thouless (dAT) transition for three-dimensional (3D)
spin glasses in a field is still debated. We introduce a new computational method to define the
spin-glass susceptibility, which is robust against the broad tail in the overlap distribution that undermines conventional analyses. Applying this approach to the Edwards-Anderson
spin-glass model in 2D and 3D, and contrasting with the 3D Ising (without disorder) and mean-field
spin-glass models, we find a stark difference: the locus of susceptibility maxima bends to the right in the field-temperature plane for the Ising and 2D
spin-glass cases, indicating a supercritical crossover line, but bends to the left for the mean-field and 3D
spin glasses - a signature of the dAT line. Finite-size scaling further suggests that the peak susceptibility diverges with system size in 3D
spin glasses under a field, while saturating in 2D. These results provide direct numerical evidence for the dAT transition in 3D, supporting the replica
symmetry breaking scenario.
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Materials Science
Mapping Metastable Magnetic Textures in (Fe0.5Co0.5)5GeTe2 with in-situ Lorentz Transmission Electron Microscopy
Reed Yalisove, Hongrui Zhang, Xiang Chen et al. (+5 more)
Topologically protected
magnetic textures are a promising route to low-energy control of magnetism, but they are most often studied away from ambient conditions, typically at low temperatures and high
magnetic fields. Here we use in-situ Lorentz transmission electron microscopy with control of temperature and
magnetic field to investigate the skyrmion metastability in (Fe0.5Co0.5)5GeTe2 (FCGT). By field-cooling FCGT in
magnetic fields of different magnitude to different base temperatures and then removing the applied field, we create meta(stable) zero-field
magnetic states. We use this method to build a phase diagram of the zero-field metastable
spin structures in FCGT, which will be critical for selecting the desired topologically-protected
spin state for future studies to manipulate magnetism with stimuli such as electric current, electric field, mechanical strain, and more.
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All authors Reed Yalisove, Hongrui Zhang, Xiang Chen, Fanhao Meng, Jie Yao, Robert Birgeneau, Ramamoorthy Ramesh, Mary C. Scott
Other Condensed Matter · Cross-listed from quant-ph
Jia-Chen Tang, Xu-Yang Hou, Yu-Huan Huang et al. (+1 more)
We investigate the post-quench dynamics of the
quantum geometric tensor (QGT) of 1D periodic systems with a suddenly changed
Hamiltonian. The diagonal component with respect to the
crystal momentum gives a metric corresponding to the variance of the time-evolved position, and its coefficient of the quadratic term in time is the group-velocity variance, signaling ballistic wavepacket dispersion. The other diagonal QGT component with respect to time reveals the energy variance. The off-diagonal QGT component features a real part as a covariance and an imaginary part representing a quench-induced
curvature. Using the Su-Schrieffer-Heeger (SSH) model as an example, our numerical results of different quenches confirm that the post-quench QGT is governed by physical quantities and local
geometric objects from the initial state and post-quench bands, such as the Berry connection, group velocities, and energy variance. Furthermore, the connections between the QGT and physical observables suggest the QGT as a comprehensive probe for nonequilibrium phenomena.
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All authors Jia-Chen Tang, Xu-Yang Hou, Yu-Huan Huang, Hao Guo. Chih-Chun Chien
Materials Science
Atomic and Electronic Structure of Strongly Charged Domain Walls in van der Waals {\alpha}-In$_2$Se$_3$
Gillian Nolan, Edmund Han, Shahriar Muhammad Nahid et al. (+4 more)
Here, we use atomic resolution scanning transmission electron microscopy (STEM) and first principles calculations to study the atomic and electronic structure of strongly charged domain walls in $\alpha$-In$_2$Se$_3$. STEM imaging and density functional theory (DFT) show that head-to-head (HH) domain walls contain a layer of nonpolar $\beta$-In$_2$Se$_3$, whereas tail-to-tail (TT) domain walls are atomically abrupt. We apply 4D STEM and multislice electron ptychography to map ferroelectric domains in 2D and 3D, showing that nearly $180^\circ$ domain walls exhibit complex, curved 3D structures that differ from ideal $180^\circ$ structures. Band structure calculations show localized conducting states within a $\sim$ 1 nm thick layer at both HH and TT domain walls, such as a midgap state at the $\beta$ layer of the HH domain wall. These properties make strongly charged domain walls in $\alpha$-In$_2$Se$_3$ excellent candidates for realizing 2D electron or hole gases and domain wall engineering in van der Waals ferroelectrics.
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All authors Gillian Nolan, Edmund Han, Shahriar Muhammad Nahid, Patrick Carmichael, Arend M. van der Zande, André Schleife, Pinshane Y. Huang
Soft Condensed Matter
Boson peak in the dynamical structure factor of network- and packing-type glasses
Hideyuki Mizuno and Emi Minamitani
Glasses are structurally disordered solids that host, in addition to crystalline-like
phonons, vibrational excitations with no direct phononic counterpart. A long-standing universal signature is the excess vibrational density of states~(vDOS) over the Debye prediction, known as the
boson peak~(BP), which has been extensively reported via inelastic
neutron and X-ray scattering measurements of the dynamical structure factor $S(q,\omega)$. Here we quantify the vDOS directly from dynamical-structure-factor data and clarify the microscopic origin of the BP. We contrast two routes to extract the vDOS from $S(q,\omega)$: (i) using high-wavenumber $q$ data beyond the Debye wavenumber $q_D$ to access predominantly incoherent scattering and recover the vDOS in a manner analogous to velocity-autocorrelation-based approaches; and (ii) integrating $S(q,\omega)$ over the low-$q$ regime below $q_D$, which enables a decomposition of the vDOS into contributions from distinct wavenumber sectors and thereby provides direct access to the spatial character of vibrational modes. Focusing on the second route, we demonstrate that the BP in the vDOS emerges as the spectral consequence of a dispersionless excitation band in $S(q,\omega)$. Our main results are obtained from molecular-dynamics simulations, and we further show that the same mechanism is captured by an effective-medium theory for random spring networks, providing a unified interpretation that connects the excess vDOS to the wavenumber-resolved structure of vibrational excitations in glasses.
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Materials Science
Altermagnetic spin-split Fermi surfaces in CrSb revealed by quantum oscillation measurements
Taichi Terashima, Yuya Hattori, David Graf et al. (+5 more)
We report a comprehensive
quantum oscillation study of the prototypical altermagnet CrSb, combining high-field magnetotransport and torque measurements with DFT + $U$ calculations including
spin-orbit coupling. Multiple
quantum oscillation frequencies were observed and tracked over wide angular ranges. The measured frequency branches are consistently explained by the
spin-split
Fermi surfaces arising from the altermagnetic electronic structure. Our determined
Fermi surface reveals that bands 1 and 2 form closed pockets centered at the A point, rather than the tubular $c$-axis-open sheets or $\Gamma$-centered closed pockets proposed in previous studies. Our findings establish the
Fermi-surface
topology of CrSb and provide a firm basis for exploring emergent phenomena in altermagnetic materials.
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All authors Taichi Terashima, Yuya Hattori, David Graf, Takahiro Urata, Tomoki Yoshioka, Wataru Hattori, Hiroshi Ikuta, Hiroaki Ikeda
Strongly Correlated Electrons · Cross-listed from physics.comp-ph
Transformer Learning of Chaotic Collective Dynamics in Many-Body Systems
Ho Jang and Gia-Wei Chern
Learning reduced descriptions of chaotic many-body dynamics is fundamentally challenging: although microscopic equations are Markovian, collective observables exhibit strong
memory and exponential sensitivity to initial conditions and prediction errors. We show that a self-
attention-based
transformer framework provides an effective approach for modeling such chaotic collective dynamics directly from time-series data. By selectively reweighting long-range temporal correlations, the
transformer learns a non-Markovian reduced description that overcomes intrinsic limitations of conventional recurrent architectures. As a concrete demonstration, we study the one-dimensional semiclassical Holstein model, where interaction quenches induce strongly nonlinear and chaotic dynamics of the charge-density-wave order parameter. While pointwise predictions inevitably diverge at long times, the
transformer faithfully reproduces the statistical "
climate" of the chaos, including temporal correlations and characteristic decay scales. Our results establish self-
attention as a powerful mechanism for learning effective reduced dynamics in chaotic many-body systems.
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Strongly Correlated Electrons
Design and fabrication of guiding patterns for topography-based searching of 2D devices for scanning tunneling microscopy measurements
Huandong Chen, Hong Li, Yutao Li et al. (+4 more)
We report the design and fabrication of guiding patterns for topography-based searching of two-dimensional (2D) devices for scanning tunneling microscopy (STM) measurements. Sub-micron
geometric coordinate markers were etched into SiO2/Si wafers, serving as both substrates for 2D device integration and guiding maps for sample
navigation. Here, we used a monolayer
graphene/h-BN device with an active area of smaller than 20 um x 20 um as a model system and demonstrated that the device could be reliably located in STM solely through topographic imaging of the guiding patterns and in situ stage calibration, without reliance on optical viewports or capacitive sensing. Atomically resolved topographic imaging and tunneling spectroscopy were also obtained. Our proposed
navigation strategy is fully compatible with standard device fabrication procedures and requires no hardware modification to existing STM setups. As such, it offers a practical alternative for locating miniaturized devices in STM, shedding light on studying emerging
quantum phenomena in 2D systems.
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All authors Huandong Chen, Hong Li, Yutao Li, He Zhao, Ming Lu, Kazuhiro Fujita, Abhay N. Pasupathy
Materials Science
C2NP: A Benchmark for Learning Scale-Dependent Geometric Invariances in 3D Materials Generation
Can Polat, Erchin Serpedin, Mustafa Kurban et al. (+1 more)
Generative models for materials have achieved strong performance on periodic bulk
crystals, yet their ability to generalize across scale transitions to finite nanostructures remains largely untested. We introduce
Crystal-to-Nanoparticle (C2NP), a systematic
benchmark for evaluating generative models when moving between infinite crystalline unit
cells and finite nanoparticles, where surface effects and size-dependent distortions dominate. C2NP defines two complementary tasks: (i) generating nanoparticles of specified radii from periodic unit
cells, testing whether models capture surface truncation and
geometric constraints; and (ii) recovering bulk
lattice parameters and space-group
symmetry from finite particle configurations, assessing whether models can infer underlying crystallographic order despite surface perturbations. Using diverse materials as a structurally consistent testbed, we construct over 170,000 nanoparticle configurations by carving particles from supercells derived from DFT-relaxed
crystal unit
cells, and introduce size-based splits that separate interpolation from extrapolation regimes. Experiments with state-of-the-art approaches, including
diffusion, flow-matching, and variational models, show that even when losses are low, models often fail geometrically under distribution shift, yielding large
lattice-recovery errors and near-zero joint accuracy on structure and
symmetry. Overall, our results suggest that current methods rely on template memorization rather than scalable physical generalization. C2NP offers a controlled, reproducible framework for diagnosing these failures, with immediate applications to nanoparticle catalyst design, nanostructured hydrides for hydrogen storage, and materials discovery.
Dataset and code are available at https://github.com/KurbanIntelligenceLab/C2NP.
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All authors Can Polat, Erchin Serpedin, Mustafa Kurban, Hasan Kurban
Mesoscale and Nanoscale Physics
J. X. Dai and Y. X. Zhao
Symmetry-protected topological phases have been a central theme in condensed matter physics and beyond over the past two decades. Most efforts have focused on topological classifications of physical systems under given
symmetries, while the intrinsic
topology of the
symmetries themselves has received much less
attention. Here, we show that, in generic non-interacting spinless
crystals, the spacetime inversion
symmetry $PT$ naturally carries a real vector-bundle structure whose
topology is characterized by Stiefel–Whitney (SW) classes. In contrast to previous work, where SW classes were used to describe the
topology of real valence bundles protected by $PT$, we identify SW classes associated to the $PT$
symmetry itself. These
symmetry SW classes can endow the total real bundle of a $PT$-symmetric band structure with nontrivial
topology, overturning the common assumption that the total bundle is always trivial. As a consequence, valence and conduction bands can exhibit asymmetric SW classes, in sharp contrast to the usual symmetric scenario. We further demonstrate that the
symmetry SW classes provide a refined distinction between atomic
insulator phases. Our results underscore the importance of treating
crystal symmetries as topological objects in their own right, rather than focusing solely on the
topology of energy bands.
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Materials Science
Light-Emitting Diodes with Micrometer-Thick Perovskite Charge Transport Layers
Sang-Hyun Chin
Over the past few decades, thin-film optoelectronic devices have shown significant advancements. Light-emitting diodes (LEDs) based on organic materials,
polymers,
quantum dots, as well as metal halide perovskites have achieved remarkable efficiencies and long lifetimes, making them ideal for applications in full-color displays and solid-state lighting. These devices typically feature a layered structure, with the light-emitting layer positioned between charge transport layers and two electrodes. This perspective reviews recent progress in LEDs utilizing perovskite charge transport layers and suggests potential pathways for further development in this field.
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Mesoscale and Nanoscale Physics
Fundamental Tests of Quantum Geometric Bounds in Ionic and Covalent Insulators using Inelastic X-Ray Scattering
David Bałut, Barry Bradlyn, Marcus D. Collins et al. (+1 more)
Quantum geometry underlies many fundamental properties of materials, but it has remained largely inaccessible to direct experiment. Here we demonstrate that inelastic x-ray scattering (IXS) provides a direct, quantitative probe of
quantum geometry and
quantum information in solids. Studying two prototype
insulators, covalently bonded diamond and ionically bonded LiF, we measure the density response and experimentally determine the
quantum Fisher information, the associated Bures metric, and the electron localization length. These measurements enable a quantitative comparison of
quantum geometry for two distinct bonding environments. We find that the dimensionless
quantum weight, $aK(q)$, which quantifies the longitudinal localization of
quantum information, is constrained by fundamental electrostatic bounds in both materials. Crucially, the
quantum weight of diamond exceeds that of LiF, indicating that covalent bonds exhibit a higher degree of delocalization and higher density of
quantum information than the ionic bonds. Our results establish a direct experimental relationship between
quantum information, electron localization, and chemical bonding, and identify IXS as a powerful tool for measuring
quantum geometry in materials.
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All authors David Bałut, Barry Bradlyn, Marcus D. Collins, Peter Abbamonte
Mesoscale and Nanoscale Physics
Transport spin polarization in RuO$_2$ films
Alexandra J. Howzen, Sachin Gupta, Gavin Burnell et al. (+1 more)
Altermagnets host
spin-split electronic bands without net magnetization, enabling
spin-polarized transport in the absence of conventional ferromagnetism. RuO$_2$ has been proposed as a candidate altermagnet, yet experimental reports remain conflicting, particularly between bulk-sensitive probes and thin-film measurements. Here we investigate the electronic transport properties of epitaxial RuO$_2$ thin films using anomalous
Hall effect measurements and point-contact Andreev reflection spectroscopy. We observe transport
spin polarization and a strongly orientation-dependent anomalous
Hall response, while magnetometry reveals no detectable net magnetization. The anomalous
Hall effect appears only in ultrathin (110)-oriented films, consistent with
symmetry-driven Néel-vector physics, and the measured transport
spin polarization is systematically higher for (110)-oriented films than for (001)-oriented films, consistent with the crystallographic anisotropy of the
spin-split bands. These results are consistent with altermagnetic behavior in RuO$_2$, with the experimentally accessible signatures confined to near-surface regions. They also establish superconducting transport spectroscopy as a metrology for identifying and characterizing altermagnet candidates.
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All authors Alexandra J. Howzen, Sachin Gupta, Gavin Burnell, Nathan Satchell