Strongly Correlated Electrons
Twinning of domains and spin anisotropy in K$_5$Fe$_4$Ag$_6$Te$_{10}$
Jiayu Guo, Hengyang Zhong, Dongsheng Yuan et al. (+12 more)
The Fe-based
superconductors are derived from metallic parent compounds with nematic and stripe
magnetic orders, which lead to two types of
magnetic domains. Recently it was found that K$_5$Fe$_4$Ag$_6$Te$_{10}$ (KFAT), an Fe-based
semiconductor, exhibits similar nematic and stripe
magnetic orders, and is thus an analogue to the Fe-based
superconductors in the limit of localized electrons. In this work, the superstructure and
magnetic domains of KFAT are elucidated by fully mapping the reciprocal space using time-of-flight single
crystal neutron diffraction. In KFAT, Fe and Ag atoms order to form a $\sqrt{5}\times\sqrt{5}$ superstructure containing $2\times2$ Fe blocks, which leads to two superstructure domains with identical main Bragg peaks but distinct superstructure peaks. Below $T_{\rm N}\approx35$~K,
magnetic and nematic orders break in-plane rotational
symmetry of the tetragonal $\sqrt{5}\times\sqrt{5}$ superstructure, and further give rise to two
magnetic domains. These four equally populated domains account for the complex scattering pattern observed in our time-of-flight elastic
neutron scattering measurements. Using polarized
neutron scattering, we demonstrate a prominent
spin anisotropy with an easy-plane spanned by the $c$-axis and the intra-block antiferromagnetic Fe-Fe bond direction. Such an anisotropy at ${\bf q}\neq0$ persists well above $T_{\rm N}$, accounts for the in-plane ${\bf q}=0$
magnetic anisotropy observed in uniaxial-strained KFAT, and offers an indicator for discovering similar piezomagnetic effects in other materials.
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All authors Jiayu Guo, Hengyang Zhong, Dongsheng Yuan, Xuejuan Gui, Youzhe Chen, Nathan Giles-Donovan, Naomi Kawamura, Masaaki Matsuda, Yaohua Liu, Feng Ye, Rongyan Chen, Robert J. Birgeneau, Xingye Lu, Jincheng Wang, Yu Song
Soft Condensed Matter
Investigating the Nature of Discontinuous Shear Thickening: Beyond a Mean-Field Description
Jetin E. Thomas, Abhay Goyal, Deshpreet Singh Bedi et al. (+3 more)
Dense suspensions can undergo a dramatic increase in viscosity at a critical value of the shear stress. This phenomenon, termed discontinuous shear thickening (DST), has been attributed to an increase in the fraction of particle interactions becoming frictional with increasing shear stress, and a successful mean-field theory has been developed to explain various accompanying rheological properties. On a microscopic scale, however, conventional structural analysis measures such as the grain-position pair correlation function show no significant changes with the onset of DST, though recent work has shown that similar analysis in the dual space of contact forces does lead to marked changes at this transition. Furthermore, experimental results have suggested the existence of higher-order microscopic correlations and the importance of incorporating fluctuations away from a mean-field description. To this end, we use a higher-order cluster analysis tool to study the force networks obtained from simulations of dense suspensions to construct an effective interaction potential in force space. We show that there are significant changes occurring in this potential as a function of density and stress close to DST. We discuss the implications of these observations on an emergent field theory of the DST transition.
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All authors Jetin E. Thomas, Abhay Goyal, Deshpreet Singh Bedi, Abhinendra Singh, Emanuela Del Gado, Bulbul Chakraborty
Statistical Mechanics · Cross-listed from hep-th
Spectral Chaos from a Fluctuating Quantum Horizon
Chong-Sun Chu
Black holes are conjectured to be maximally chaotic, with their
quantum spectra expected to exhibit universal random-
matrix correlations. This expectation, however, has so far rested largely on holographic descriptions or on many-body models in which randomness is introduced rather than derived from the microscopic degrees of freedom of the horizon itself. In the horizon
matrix model, the fuzzy sphere supports highly degenerate parton states whose multiplicity accounts for the black-hole
entropy. We show that
quantum fluctuations of the horizon geometry lift this degeneracy and generate an ensemble of one-parton
Hamiltonians. Both the operator structure and the rank-dependent covariance of this ensemble are determined by the microscopic model, rather than fixed by quenched couplings. Despite this structured covariance, the resulting spectra exhibit GOE, GUE, and GSE statistics dictated by their antiunitary
symmetry classes, with the adjacent-gap statistic becoming increasingly self-averaging with
matrix size. The model also realizes the universal Pandey–Mehta orthogonal-to-
unitary crossover, with the crossover scale determined by the microscopic
geometric covariance. A rank-resolved variance analysis shows that the fluctuation strength remains broadly distributed across tensor ranks up to the microscopic cutoff, providing a microscopic basis for the observed Wigner–Dyson universality and effectively nonlocal dynamics. The antiunitary
symmetry acts directly on the fuzzy-sphere geometry, so the Dyson class of a conditional
Hamiltonian is determined by the antiunitary
symmetry of the underlying
quantum geometry. This provides a microscopic counterpart of the Stanford–Witten relation between geometry and random-
matrix universality in JT
gravity. These results establish a microscopic route from
quantum horizon geometry to black-hole spectral chaos.
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Superconductivity
Growth of superconducting boron doped diamond on 4inch silicon wafers
Soumen Mandal and Oliver A Williams
Superconducting boron-doped diamond (BDD) films were grown on 4-inch silicon wafers by microwave
plasma chemical vapour deposition using gas-phase B/C ratios ranging from 6536 to 36421 ppm. Surface morphology, boron incorporation and superconducting properties were investigated as a function of gas-phase boron concentration. No systematic variation in apparent lateral grain size was observed across the series. Superconductivity was observed in all films except that grown at a B/C ratio of 6536 ppm within the measured temperature range down to 2 K. The superconducting transition temperature initially increased with increasing B/C ratio, reaching a maximum T$_c$ of 4.03 K at 24691 ppm, before decreasing at higher gas-phase B/C ratios. The corresponding resistive upper critical field at 2 K reached 3.091 T. Raman spectroscopy showed an increase in boron incorporation with increasing gas-phase B/C ratio up to 30303 ppm, followed by a slight decrease at 36421 ppm. Spatial measurements across the film grown at 24691 ppm showed T$_c$ values of 4.02, 4.19 and 3.33 K at the centre, intermediate and edge positions, respectively, with Raman spectroscopy showing a corresponding spatial variation in boron concentration. Comparison with previous growth on 2-inch wafers showed that substantially higher gas-phase B/C ratios were required to obtain comparable boron concentrations and superconducting properties on 4-inch wafers, indicating reduced boron incorporation efficiency during large-area growth. These results demonstrate the feasibility of producing superconducting BDD over a substantial area of a 4-inch silicon wafer while identifying boron incorporation and radial uniformity as key parameters for further wafer-scale optimisation.
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Strongly Correlated Electrons · Cross-listed from quant-ph
Variational Real-Time Dynamics on Reduced Operator Manifolds
Aeishah Ameera Anuar, PV Sriluckshmy, Riccardo Rossi et al. (+1 more)
Accurate real-time simulation of correlated
quantum systems remains challenging for both classical methods and near-term
quantum hardware. We introduce operator-projected variational
quantum real-time
evolution (OVQRTE), which updates a parameterized
circuit by enforcing the Ehrenfest equations for a selected set of observables. OVQRTE requires only expectation-value measurements, while the choice of operator set enables a systematic trade-off between accuracy and measurement cost, substantially reducing
quantum-resource requirements relative to existing variational real-time-
evolution algorithms. After implementing OVQRTE dynamics of Heisenberg model on a simulator, we
benchmark the
algorithm for the Anderson impurity models on the IQM Emerald superconducting processor using up to 24
qubits. We further use OVQRTE to sample computational-basis states for
quantum-selected configuration interaction (QSCI), enabling the calculation of the ground-state energy and density of states within a self-consistent ghost-Gutzwiller Ansatz (gGut)
embedding loop. Our results establish OVQRTE as a promising approach for investigating correlated condensed-matter systems on near-term
quantum hardware.
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All authors Aeishah Ameera Anuar, PV Sriluckshmy, Riccardo Rossi, Fedor Simkovic
Disordered Systems and Neural Networks
Disorder-Tailored Delocalization
Yeongjun Kim, Supriyo Ghosh and Sergej Flach
We derive disorder fields tailored by the details of a choice of a delocalized wave function. We first investigate the unidirectional Hatano-Nelson chain and its localization properties under $M$-base diagonal disorder with variable weights. The spectrum forms loops in the complex plane and the loop parameter is a good
quantum number similar to a momentum. All eigenstates are subexponentially `localized', i.e. the logarithm of the absolute value of the wave function performs a random walk in space, and are characterized by a corresponding length scale $\xi_{sel}$ as shown in 1998 by Silvestrov for the general Hatano-Nelson chain. For $M=2$ real-valued binary disorder with equal weights the model was solved in Zeitschrift für Naturforschung A 81 421, yielding Cassini oval spectral loops and a diverging subexponential localization length for two eigenstates and for disorder weaker than a critical value set by the hopping strength. When the disorder field for any $M$ and arbitrary weights is confined to circles in the complex plane with radius equal to the hopping strength, the circle center will belong to the spectrum and to one of the spectral loops, and host a plane-wave-like eigenstate with diverging $\xi_{sel}$. We generalize to tailoring on-site disorder for a given eigenstate at a given energy, for any
lattice dimension, and any hopping field (both ordered and disordered), for Hermitian and non-Hermitian systems. We exemplify by constructing a one-dimensional chain with Anderson-localized eigenstates hosting a completely delocalized one with random phases. The localization length diverges as $1/|E|^{2/3}$ upon approaching the delocalized state. Our method can be used for the systematic construction of disorder fields which host predefined eigenstates with arbitrary properties.
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Quantum Gases
Borromean Criticality in Two Dimensions
Alexandru Golic, Igor Timoshuk, Albert Samoilenka et al. (+2 more)
The characteristic feature of counterflow superfluids consisting of $N\geq 3$ components – the so-called Borromean supercounterfluids (BSCF) – is the presence of $N$ distinct elementary topological excitations (
vortices) despite having only $N-1$ independent Goldstone modes. We show that this remarkable property clearly manifests itself at the Berezinskii-Kosterlitz-Thouless-type transition from the BSCF to the normal state, under the conditions of slight to moderate deviations from the case of exact intercomponent
symmetry. More generally, our analysis also applies to any multicomponent superfluid with intercomponent drag fine-tuned to the value when certain composite
vortices compete energetically with elementary ones.
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All authors Alexandru Golic, Igor Timoshuk, Albert Samoilenka, Egor Babaev, Boris Svistunov
Materials Science
A cylindrical sintering method for more realistic grain boundaries in nanocrystalline thin films
Ankit Yadav, Lucia Bajtošová, Miroslav Cieslar et al. (+1 more)
Discrepancies between simulated and experimental mechanical properties in molecular dynamics simulations of nanocrystalline metals typically arise from the sample-construction method and the interatomic potential choice. We introduce a cylindrical sintering method to generate nanocrystalline aluminum thin-film samples with wider, more disordered grain boundaries than the usual Voronoi tessellation method, while maintaining deterministic control over grain size, shape, and orientation. Cylindrical sintered samples are benchmarked against hexagonal Voronoi references under identical conditions using both the classical Pascuet15 MEAM and tabGAP machine-learning potentials. Cylindrical sintered samples consistently show lower mechanical properties than hexagonal Voronoi samples due to their wider, more disordered grain boundaries - an effect independent of the choice of potential. Notably, changing the sample geometry and changing the interatomic potential produce comparable, additive, and independent shifts in predicted properties, highlighting that future molecular dynamics studies must hold both variables fixed for meaningful comparisons. Common neighbor and dislocation extraction analyses confirm that deformation is dominated by grain-boundary-mediated plasticity. Uniaxial tensile tests reveal an inverse Hall-Petch relationship for both sample types and both potentials, with mechanical properties decreasing monotonically as grain size reduces from 40.34 to 4.84 nm. The cylindrical sintering method offers a physically realistic, geometrically controlled alternative that bridges idealized Voronoi models and disordered experimental grain-boundary structures.
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All authors Ankit Yadav, Lucia Bajtošová, Miroslav Cieslar, Jan Fikar
Mesoscale and Nanoscale Physics · Cross-listed from hep-th
Quantum geometry of gravitons
M. Mehraeen
We uncover the
quantum geometric structure of graviton Wigner functions and stress-energy tensors via
quantum field theory in curved spacetime, revealing the phase-space geometry of spacetime and relativistic
quantum-state
manifolds. We show that the polarization mode expansion of the underlying graviton field operator is fully captured by
quantum geometry, as encoded in the spinor-helicity formalism, thereby establishing the
geometric framework from the outset. Applying this to a weak gravitational background, we demonstrate the roles of the
quantum metric and connection in describing graviton transport beyond the chiral vortical effect. We also clarify the role of the
quantum metric in normalizing the perfect-fluid graviton stress tensor within this approach. This work paves the path for explorations of multistate
Hilbert-space geometry in high-energy and gravitational physics. In addition, this framework naturally encompasses lower-
spin excitations, allowing for a unified
quantum geometric treatment of bosonic and fermionic many-body systems in condensed matter and particle physics.
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Mesoscale and Nanoscale Physics
Quasilocal transport in the integer quantised Hall effect: adiabatic separation, local Ohm's law, and Joule heating of the incompressible strips
A. Siddiki
We reassess the semiclassical route to integer
quantum Hall transport around one idea: the separation of fast, quantised cyclotron motion from a slow, self-consistently screened guiding-centre landscape. Bohr–Sommerfeld quantisation of the canonical action fixes the Landau spectrum; smooth confinement turns it into Born–Oppenheimer surfaces with adiabatic parameter $\ell|\nabla V|/\hbar\omega_c$; screening supplies the self-consistent field. Transport is quasilocal, $R_H=\int\rho_Hj_y\,dx/\int j_y\,dx$ with $j_y\propto1/\rho_l$, so within the regularised local Ohm model the incompressible strips attract the current by weight and the computed Joule-power profile follows the current profile. In linear response the intrinsic electrostatic AC correction of the frozen-profile model is reactive, $\mathrm{Im}\,R_H\propto\omega$, with $\mathrm{Re}\,R_H-R_H^{\rm DC}\propto\omega^{2}$ below $10^{-9}$ up to $2$~MHz. With the current fed back into the electrostatics at $1$–$5\,\mu$A, where the Hall drop is one to five cyclotron gaps, the driven boundary condition breaks the reflection
symmetry of the bar, the Hall drop concentrates in one strip (interchanged to $10^{-9}$ under current reversal), and the plateau narrows from its low-field flank while, for the GaAs parameters studied, its high-field edge stays at $\nu(0)=2$. A local transverse thermal closure inspired by Akera, evaluated as a post-process on the frozen profile with two
phonon-loss laws, indicates that the narrow current-carrying strips of the low-field flank may heat by of order the
lattice temperature; with the activated-heat-capacity closure the cold strip loses its stationary solution at model-dependent currents of $0.3$–$2\,\mu$A. The thermal conclusions are bounded by the loss law and by the frozen profile, and are presented as estimates.
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Strongly Correlated Electrons
Band-Saddle-Point Engineering in Mixed $A$-site $A$V$_3$Sb$_5$ Kagome Metals
Maxim Wenzel, Alexander A. Tsirlin, Andrea N. Capa Salinas et al. (+4 more)
$A$V$_3$Sb$_5$ compounds ($A$ = K, Rb, Cs) offer an experimental platform for probing the physics of kagome metals near ideal Van Hove filling. Here, we use optical spectroscopy on $A$V$_3$Sb$_5$ with mixed $A$-site compositions to reveal the effect of the alkali metal on the low-energy electronic structure. Supported by density-functional-theory calculations, we identify a band-saddle-point inversion as a chemical consequence of Cs substitution, revealing that $A$-site composition controls the orbital character of Van Hove singularities, Fermi surface
topology, and electron-
phonon interactions while leaving the kagome layer intact.
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All authors Maxim Wenzel, Alexander A. Tsirlin, Andrea N. Capa Salinas, Brenden R. Ortiz, Stephen D. Wilson, Ece Uykur, Martin Dressel
Materials Science
Evaluating Predicted Densities, Hamiltonians, and Density Matrices as Periodic SCF Initializers
Pin Chen, Jiang Li and Yutong Lu
Learned electronic states are usually evaluated by prediction error, even though their intended use is to accelerate the self-consistent-field (SCF) loop of density functional theory (DFT). We ask whether lower offline error actually yields a better SCF initializer. We construct $\rho$HD-43K, a 43,851-
crystal DFT corpus with aligned charge-density,
Hamiltonian, and density-
matrix labels, and extend the solver workflow to inject all three predicted states. The closed-loop
benchmark compares direct converged-state prediction against residual prediction from solver-native references on a frozen test set of non-
magnetic crystals, using paired convergence, iteration, and SCF-loop timing measurements. Injecting the exact converged density
matrix or
Hamiltonian as an oracle upper bound cuts the median SCF count from 16 to one, revealing substantial acceleration headroom. Among learned inputs, direct charge-density prediction (Charge3Net-E3) accelerates about 91% of paired
crystals, saves a median of three SCF iterations, and yields a $1.18\times$ SCF-loop speedup. In contrast, the tested residual-density and
matrix initializers do not consistently improve over the standard superposition-of-atomic-densities baseline. These results establish that target-space accuracy alone is insufficient: a learned initializer must also be compatible with the nonlinear solver trajectory, and its utility must be measured in the loop.
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Materials Science
Navigating Sparse Singlet Fission Chemical Space: An Intelligent Generative-Predictive Paradigm
Longfei Lv, Li Fu, Si Zhou et al. (+2 more)
Singlet fission (SF) offers a promising route to surpass the Shockley-Queisser limit by converting a photoexcited singlet
exciton into two triplet
excitons, thereby enhancing photovoltaic energy conversion efficiency. However, realizing efficient SF process requires stringent energetic requirements among low-lying excited states that render SF molecules intrinsically rare within the vast chemical space. This extreme sparsity presents a grand challenge for molecular discovery. Due to low hit rates and trial-and-error computational waste on nonviable structures, conventional high-throughput virtual screening faces significant constraints, even when accelerated by machine learning models. Here, we establish a synergistic generative-predictive framework for the targeted inverse design of SF molecules by integrating a structure generator, a properties predictor and a multi-criteria validation workflow. By continuously coupling generative exploration with SF predictive models, the framework progressively enriches SF species and achieves a success rate of approximately 90% in generating molecules that satisfy the target SF energetic criteria. High-throughput evaluation of about 100 million generated structures with time-dependent density functional theory (TDDFT) validation of just a random 1% subset confirmed a 90.8% success rate for SF candidates. All together, we constructed an SF database of 283,559 candidates with favorable energetics of excited states and synthetic accessibility. From it, we identified a key fragment strongly associated with the requirements for SF, namely, CN([O])N(C)[O]. These findings establish an efficient route for overcoming the sparsity difficulty in SF molecular discovery and provide interpretable design principles for the development of novel excited-state functional materials.
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All authors Longfei Lv, Li Fu, Si Zhou, Lingzhi Zhao, Jijun Zhao
Materials Science
Demonstrate of High-Performance Top-Gate ALD Crystalline In2O3 Transistor Enabled by Lattice-Matched HfO2 and In2O3 Heterostructure
Kai Jiang, Chen Wang, Ziheng Wang et al. (+2 more)
In this work, we demonstrate high-mobility top-gate (TG) atomic-layer-deposited (ALD) crystalline In2O3 transistors through simultaneous interface and crystallinity engineering. First, a HfO2/In2O3/HfO2 stack is employed, enabling epitaxial-like crystallization of the ultrathin In2O3 channel, because of the
lattice matching between monoclinic phase HfO2 and cubic phase In2O3. Second, an oxygen-rich gate
insulator process is applied using high-dose O3 precursor and elevated deposition temperature, effectively suppressing oxygen scavenging during gate dielectric deposition, significantly reducing interfacial defect formation. Third, the homogeneous In-O bonding network in crystalline In2O3 exhibits substantially enhanced resistance to oxygen scavenging by source/drain contacts, which significantly improves the immunity to threshold voltage (VTH) roll-off at short channel length compared to amorphous In2O3. As a result, high-performance TG long-channel In2O3 transistors are achieved with a high mobility of 163 cm2/V s and a steep subthreshold slope of 64 mV/dec. High-performance TG short-channel In2O3 transistors with high ION of 1650 {\mu}A/{\mu}m at VD of 1 V, large on/off ratio over 1010 and VTH of -0.27 V are demonstrated. These results establish
lattice-engineered crystalline In2O3 as an effective strategy for high-mobility, aggressively scaled TG oxide transistors suitable for BEOL-compatible applications.
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All authors Kai Jiang, Chen Wang, Ziheng Wang, Zhiyu Lin, Mengwei Si
Materials Science
Ionic-Radius Mismatch as a Structural Lever for Tuning Phase Transitions and Luminescent Thermometry
A. Javaid, M. Szymczak, A. Sieradzki et al. (+1 more)
The widespread implementation of luminescence thermometers requires a comprehensive understanding of the structural factors governing their thermometric performance. Establishing such structure-property relationships is essential for the rational design of sensing materials with application-tailored characteristics. This is particularly relevant for phase-transition-based luminescence thermometers, which offer exceptionally high relative sensitivities. The systematic analysis of K3Lu(PO4)2:Eu3+ demonstrates that introducing co-dopant ions with a controlled ionic-radius mismatch provides an effective strategy for tailoring phase-transition characteristics. This approach enables both the phase-transition temperature and thermal operating range to be controlled. Specifically, the transition temperature shifts from 210 K for K3Lu(PO4)2:Eu3+ to 310 K for K3Lu(PO4)2:Eu3+,10%La3+, while the operating range broadens from 30 to 60 K. Importantly, linear correlations between the ionic-radius mismatch parameter, {\Omega}, and the phase-transition temperature, enthalpy, and
entropy provide a quantitative framework for controlling the thermodynamics of the transition through compositional engineering. Beyond luminescence thermometry, these relationships establish a general strategy for designing materials exhibiting first-order phase transitions with tailored thermodynamic characteristics, opening opportunities for their optimization across a broad range of functional applications.
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All authors A. Javaid, M. Szymczak, A. Sieradzki, L. Marciniak
Materials Science
Re4+ Luminescence as a Highly Sensitive Alternative to Ruby for Optical Pressure Sensing
Yeshan Wu, Maja Szymczak, Lukasz Marciniak et al. (+5 more)
Luminescence-based remote pressure sensing provides a powerful approach for pressure determination under conditions where conventional contact methods are difficult to implement. Although ruby remains the undisputed gold standard among luminescent pressure indicators, its relatively low pressure sensitivity and susceptibility to temperature variations represent important limitations. Therefore, in this work, Cs2HfCl6:Re4+ is proposed as an alternative luminescent pressure indicator exhibiting a 15-fold higher pressure sensitivity (6.93 nm GPa-1) than ruby while maintaining a comparable thermal sensitivity, making it a particularly attractive material for optical manometry. Furthermore, Cs2HfCl6:Re4+ enables ratiometric pressure readout, providing a high relative pressure sensitivity reaching 175.1% GPa-1. To the best of our knowledge, this work represents the first demonstration of Re4+ luminescence for pressure sensing, introducing a new class of luminescent pressure indicators and opening new opportunities for the development of highly sensitive optical manometers based on Re4+-activated materials.
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All authors Yeshan Wu, Maja Szymczak, Lukasz Marciniak, Yifei Yu, Shuailing Ma, Tian Cui, Laihui Luo, Peng Du
Materials Science
Multiple Linear Regression-Enhanced RGB-based Luminescence Thermometry for High-sensitivity Thermal Readout
Y. Abe, M. Szymczak, Miguel A. Hernandez-Rodriguez et al. (+2 more)
The practical implementation of phosphors for luminescence-based thermal sensing and imaging requires simple, user-friendly approaches that enable convenient and sensitive temperature readout. To the best of our knowledge, this is the first demonstration of combining RGB-based thermal imaging using a conventional digital camera with multiple linear regression (MLR) to achieve straightforward and highly sensitive temperature determination and spatially resolved thermal imaging. Importantly, the implementation of the MLR approach enhances the relative sensitivity by more than 3-fold, compared with conventional analysis based solely on the G/R or B/R intensity ratios. The application of Ca3Al2O6:Mn2+-Ce3+ as a luminescent temperature probe, in which the intensity ratio between the Ce3+ and Mn2+ emission bands exhibits a pronounced temperature dependence, enables temperature readout through several complementary approaches. These include conventional luminescence intensity ratio thermometry (SR = 1.46% K-1), analysis of the CIE 1931 chromaticity coordinates (SRx = 0.45% K-1 and SRy = 0.14% K-1), as well as RGB-based thermal sensing and imaging using a digital camera. This
multimodal optical response, together with the accessibility of camera-based readout and the substantial sensitivity enhancement enabled by MLR, establishes a practical strategy for spatially resolved luminescence thermometry.
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All authors Y. Abe, M. Szymczak, Miguel A. Hernandez-Rodriguez, M. Runowski, L. Marciniak
Soft Condensed Matter
Spontaneous Vortex Instability in Active Nematics
Niels de Graaf Sousa, Kristian Thijssen and Amin Doostmohammadi
One of the defining results in the study of active matter is the spontaneous flow instability, through which a homogeneous, uniformly aligned state breaks translational
symmetry along a single direction and develops sustained flow. The
vortex state that emerges at higher activity has instead been attributed to nonlinear dynamics. Using a Floquet-type linear stability analysis, we show that no such mechanism is required: the flowing state undergoes a secondary, zigzag instability that breaks the remaining translational
symmetry and produces the
vortex state. We further identify a regime in which the flowing state ceases to exist and
vortices emerge directly from the uniformly aligned state. Under channel confinement, the instability selects a length scale that differs from the establishedactivelengthscale, andsetsthenumberofvorticesthatappear, leadingtoaconfinement- selected pattern reminiscent of a
vortex lattice, opening a route toward direct experimental tests of this instability. Full nonlinear simulations reproduce the predicted onset activities and the selected
vortex number.
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Disordered Systems and Neural Networks
Bias and Correlations in Quasiperiodicity: Impact on Localization in an Extended Aubry-André Model
Adithya J D, Ranjan Modak and Shaon Sahoo
Unlike in Anderson localization - where any amount of uncorrelated disorder localizes all eigenstates in one dimension - a one-dimensional system with quasiperiodic potential supports a richer range of localization behavior. This paper investigates the fundamental question of which potential characteristics govern localization properties. We characterize quasiperiodic potentials using two independent parameters, correlation and bias, and demonstrate that bias, in addition to correlation, critically influences localization. Through the study of an extended Aubry-André model, in which a tunable parameter allows systematic control over both the bias and correlation of the potential, we show that bias is key in determining the fraction of delocalized states. An increase in the potential strength generally enhances the tendency toward localization, while simultaneously strengthening the correlations in the quasiperiodic potential. This apparent counterintuitive behavior can be understood in terms of the bias parameter: increasing the potential strength reduces the bias, which in turn favors localization. For the family of
Hamiltonians considered, we identify two critical bias thresholds: below the lower threshold, the entire spectrum is localized, whereas below the higher threshold, at most a fraction of the states can be delocalized, precluding delocalization of the entire spectrum. To further test our framework, we examine a quasiperiodic model with zero bias and find that, despite its correlated nature, all states become localized even at very weak potential strengths - recovering the Anderson-like scenario.
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Strongly Correlated Electrons
Non-Abelian chiral spin liquid in a spin-$1$ antiferromagnet on the square lattice
Xiao-Tian Zhang, Yuan Yang, D. N. Sheng et al. (+1 more)
Non-Abelian chiral
spin liquids (CSLs) host non-Abelian anyon excitations and are promising platforms for topological
quantum computation. However, realizing non-Abelian CSLs in short-range interacting
spin systems remains elusive. Here, we study a
spin-$1$ square-
lattice model with the first- and second-neighbor bilinear ($J_1,J_2$) and biquadratic interactions ($K_1,K_2$), as well as the three-
spin scalar chiral coupling $J_{\chi}$. Inspired by the evidence of the Moore-Read state in exact diagonalization and infinite Projected Entangled Pair States calculations, we fix $J_1=1.0$, $J_2/J_1=0.623$, $K_1/J_1=-0.176$, and obtain a
quantum phase diagram for $0 \leq K_2/J_1 \leq 0.4$ and $0.3 \leq J_{\chi}/J_1 \leq 0.6$ by using the density
matrix renormalization group (DMRG) calculations. We identify a stripe antiferromagnetic phase, a Néel antiferromagnetic phase, a magnetically ordered chiral
spin state phase, and a non-Abelian CSL phase emerging near the boundaries of the ordered phases. The unbiased DMRG results provide strong evidence for the Moore-Read state, including the three topological sectors, the quantized
spin Chern number $C=1$, and the level counting of low-lying
entanglement spectra which is consistent with the chiral SU(2)$_2$ conformal field theory. Our results may shed new light on searching for non-Abelian CSLs in other higher-
spin ($S > 1/2$) systems with short-range couplings.
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All authors Xiao-Tian Zhang, Yuan Yang, D. N. Sheng, Shou-Shu Gong
Strongly Correlated Electrons
Observation of complex orbital order in MnV2O4
Chihaya Koyama, Shunsuke Kitou, Taishun Manjo et al. (+8 more)
Orbital ordering in vanadium spinel oxides with a geometrically frustrated pyrochlore structure has been a subject of controversy, owing to competing theoretical models and the absence of direct experimental evidence. Here we combine high-precision single-
crystal synchrotron x-ray diffraction with core differential
fourier synthesis to visualize the valence electron density (VED) of the orbital-ordered ground state in real space. By carefully investigating multiple-scattering artifacts, we identify the low-temperature structure as belonging to the I41/amd space group. The reconstructed VED around the V sites reveals an orbital-ordered state distinct from both previously proposed real- and complex-orbital models. Our results resolve the long-standing controversy in MnV2O4 and establish a route to identifying orbital states in frustrated
spin-orbital systems.
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All authors Chihaya Koyama, Shunsuke Kitou, Taishun Manjo, Yuiga Nakamura, Takeshi Hara, Naoyuki Katayama, Takuro Katsufuji, Ryotaro Arita, Yusuke Nomura, Hiroshi Sawa, Taka-hisa Arima
Materials Science
Scalable construction of force-constant basis sets for large-scale anharmonic lattice-dynamical calculations
Atsuto Seko and Atsushi Togo
A projector-based formulation of force constants in crystalline materials provides a systematic framework for constructing force-constant bases and determining force constants from force–displacement
datasets while rigorously satisfying
crystal symmetry, permutation
symmetry, and translational invariance. In this work, we develop an efficient
eigenvalue solver for projection
matrices and integrate it into the projector-based framework. The proposed method substantially reduces the computational cost and enables practical calculations for large-scale systems, low-
symmetry crystals, and higher-order force constants that are difficult to treat using conventional approaches. Applications to self-consistent
phonon calculations for assessing the grain-boundary excess free energy,
lattice thermal conductivity calculations in complex compounds, and fourth-order force-constant estimations demonstrate the efficiency and robustness of the proposed framework for large and complex materials systems.
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Materials Science
Thermally stimulated depolarization in hafnium oxide: experiment and numerical simulation
Yu. N. Novikov, D. E. Temnov, E. A. Volgina et al. (+2 more)
This paper presents an experimental and theoretical study of thermally stimulated depolarization (TSD) in hafnium oxide. Three different models for the probability of trap ionization are considered: the Frenkel effect and two variants of the multiphonon trap ionization mechanism, the multiphonon ionization mechanism of isolated traps at low trap concentrations and
phonon-assisted tunneling between neighboring traps at high trap concentrations. The best agreement between the TSD experiment and theory is observed for the multiphonon ionization mechanism of isolated traps. Similar thermal energies of electron and hole traps in HfO2 are obtained ~ 1.3 eV.
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All authors Yu. N. Novikov, D. E. Temnov, E. A. Volgina, M. S. Lebedev, V. A. Gritsenko
Disordered Systems and Neural Networks · Cross-listed from nlin.SI
Multivariable Painleve'-II equation: connection formulas for arbitrary system size
Nikolai A. Sinitsyn
Connection formulas for the asymptotic solutions of a system of n> 1 coupled Painleve'-II equations with
symmetry-breaking parameters are written explicitly. An asymptotically exact WKB approach to these formulas relies on the
quantum-mechanical independent crossing approximation for an explicitly time-dependent Schroedinger equation.
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Strongly Correlated Electrons
Heisenberg-like critical behavior in the quasi-two-dimensional metallic ferromagnet LaCrSb3
Qianhui Mao, Haotian Deng, Bin Chen et al. (+1 more)
LaCrSb3 is a material exhibiting both quasi-two-dimensional
spin fluctuations and three-dimensional
magnetic interaction characteristics. By measuring the isothermal magnetization of single-
crystals and conducting a systematic critical behavior analysis, we clarify the critical properties of its ferromagnetic phase transition and the intrinsic
magnetic interaction mechanism. Based on high-precision isothermal magnetization data measured in the vicinity of the critical point, the Curie temperature for the ferromagnetic-paramagnetic phase transition is determined to be TC = 126 K, with the critical exponents obtained as $\beta$ = 0.376, $\gamma$ = 1.417 and $\delta$ = 4.76 via the self-consistent iterative method based on the Arrott-Noakes equation. The reliability of these critical exponents is verified by the Widom scaling law, the
magnetic state scaling equation and other analyses. A comparison with theoretical models demonstrates that the critical behavior of the
magnetic phase transition in this system basically belongs to the universality class of the three-dimensional Heisenberg model. This conclusion is further confirmed by the distance-dependent decay behavior of the exchange interaction J(r), revealing the dominant role of isotropic direct exchange interactions in this system. Finally, drawing on research findings of other quasi-two-dimensional
magnetic materials, this work proposes that LaCrSb3 may exhibit finite-temperature
magnetic order in the two-dimensional limit, thereby possessing important theoretical research significance and promising practical application prospects.
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All authors Qianhui Mao, Haotian Deng, Bin Chen, Jinhu Yang
Mesoscale and Nanoscale Physics
1D Interface-Induced Real-Space Berry Curvature Gradient Encoded in SpinValley-Coupled Nonlinear Photocurrent in Lateral Heterostructure
Suman Kumar Chakraborty, Jinu James, Biswajeet Nayak et al. (+6 more)
Symmetry breaking enables helicity-dependent optoelectronic responses in
quantum materials. In two-dimensional transition-metal dichalcogenides (TMDs), circular photocurrent (CPC) is typically observed under oblique illumination via the circular
photon drag effect, while realization of the intrinsic circular photogalvanic effect (CPGE) under normal incidence remains challenging. Here, we report a clear signature of CPGE in chemical vapor deposition-grown monolayer 2D lateral
heterostructure (LHS). By probing the nonlocal photocurrent across the 1D hetero-interface, we observe a helicity-dependent photocurrent consistent with a
spin-valley-coupled CPGE-dominated mechanism driven by interface-induced Berry-
curvature asymmetry, i.e., Berry
curvature dipole. Spatially and spectrally resolved measurements under selective excitation of the MoSe2, WSe2, and the interface regions exhibit distinct magnitudes and polarities of the CPG responses. These contrasting behaviors highlight the opposite
spin-valley dichroism for MoSe2 and WSe2, as well as enhanced valley mixing at the 1D interface. Our findings establish LHS as a robust platform for realizing a hetero-interface-induced CPGE-like response and highlight its potential for valleytronics and optospintronics.
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All authors Suman Kumar Chakraborty, Jinu James, Biswajeet Nayak, David Tebbe, Purbasha Ray, Christoph Stampfer, Bernd Beschoten, Lutz Waldecker, Prasana Kumar Sahoo
Disordered Systems and Neural Networks · Cross-listed from quant-ph
Universal Defect Statistics in Reverse Quenches
Eduard J. Braun, Daniel Rubin, Margaux Cartier et al. (+2 more)
We derive an extension of the generalized Kibble-Zurek mechanism (KZM), which provides a
stochastic approach to defect formation, to reverse quench protocols. While the universal scaling behavior of defects in reverse quenches has been observed previously in certain 1D chains, we argument from a probability-theoretical perspective that this scaling persists in general, and is given by the double of the defect density variance in forward quenches. We validate these results analytically for the one-dimensional transverse field Ising model and numerically for its bond-disordered variant governed by an infinite randomness fixed point. Starting from the paramagnetic phase, this protocol relies solely on global control of the system's
magnetic field and global magnetization measurements, enabling the extraction of critical exponents without microscopic access to individual defects. This approach offers a robust and experimentally feasible method for probing
quantum critical behavior through entirely global operations.
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All authors Eduard J. Braun, Daniel Rubin, Margaux Cartier, Gerhard Zürn, Matthias Weidemüller
Materials Science
Quantitative control and recording of materials-synthesis processes using an automated experimentation platform
Yusuke Hashimoto, Takaya Muramoto, Hikari Terada et al. (+3 more)
Data-driven materials development requires the collection of large amounts of high-quality materials data. Full autonomy of materials experiments is anticipated, but its technical hurdles are high and its adoption remains limited. In this study, we constructed a simple, easy-to-deploy automated experimentation platform that focuses not on full autonomy but on the reliable automation and quantitative recording of experimental processes. Specifically, commercially available instruments such as
robot arms, electric pipettes, web cameras, and an electronic balance are combined, components such as fixtures are fabricated with a 3D printer, and the instruments are operated by control code generated by an AI
agent based on a large
language model. As a demonstration, we applied the platform to a two-solution mixing experimental system and synthesized ZIF-8, a metal-organic framework. A white suspension phase was observed in the product, and X-ray diffraction measurements confirmed that it was ZIF-8. We also found that its particle size distribution depends strongly on the solution dispensing speed of the electric pipette, which is a parameter that is difficult to control or record in manual operation. This dependence was reproduced in repeated runs, confirming the repeatability of the automated synthesis. This result is a good example showing that the control and recording of process parameters that are rarely quantified in manual work can govern the quality of materials data. All control code, CAD models, and documentation are made publicly available to encourage the spread of laboratory-scale automation of experiments.
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All authors Yusuke Hashimoto, Takaya Muramoto, Hikari Terada, Harim Song, Yuan Wang, Takaaki Tomai
Materials Science
Machine Learning Guided CALPHAD Design of Ru-Stabilized BCC B2 Refractory Alloys
Nathan Peterson, Avik Mahata, Nick Beaver et al. (+1 more)
Refractory
alloys with a ductile body-centered-cubic (BCC)
matrix strengthened by ordered B2 precipitates offer a high-temperature analogue to the gamma/gamma-
prime architecture of Ni-based superalloys. Ruthenium is particularly attractive as a B2 stabilizer because RuHf, RuZr, and RuTi can retain ordered phases well above 1300 C. In this work,
equilibrium CALPHAD calculations were coupled with random-forest-guided active learning to explore a ten-element Nb-based, Ru-bearing composition space containing Nb, Ta, Mo, V, Ru, Ti, Zr, Hf, Al, and Y at 1 at.% resolution. Across 500 CALPHAD-evaluated
alloys, the calculations reproduced the principal trends reported for the Ru-B2 design space. RuHf and RuZr remained stable to the solidus, RuTi commonly exhibited a solutionizing window, and Al-containing
alloys preferentially formed competing sigma and A15 phases. The upper bound of the BCC+B2 field increased from a median of approximately 1570 C at 5 at.% Ru to approximately 1980 C near 9-10 at.% Ru. Among the group-IV additions, Hf, Zr, and Ti produced progressively lower two-phase stability. Re-screening using physically motivated criteria identified 100
alloys satisfying requirements for high-temperature BCC+B2 stability, absence of
liquid, phase purity, and appropriate secondary-phase fraction, including 19 Ru-lean compositions and two independently reported HfRu-B2
alloys. The results establish practical compositional design rules for Ru-stabilized dual-phase refractory
alloys and identify phase-specific BCC/B2
lattice misfit as a key target for future design cycles.
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All authors Nathan Peterson, Avik Mahata, Nick Beaver, Mohsen Kivy
Materials Science
Neural-Network Solutions to Real-Space Charge Density and Generalization
Yuxuan Zeng, Tong Xie, Taoyuze Lv et al. (+1 more)
The Hohenberg-Kohn
theorem establishes that, in principle, the ground state (GS) charge density contains all GS information of a many-electron system, such that all GS observables can be expressed as functionals of the GS charge density. Conventional Kohn-Sham density functional theory requires iterative solution of the self-consistent-field equations at substantial computational cost, motivating the development of deep learning surrogates for electronic structure calculations and, in turn, accelerating computer-aided materials design. Here, we propose AIDEN, an Atomic-Interaction Density Equivariant Network for solving real-space charge density. AIDEN separates the element-dependent one-center density from environment-induced density redistribution and represents the latter through complementary atom- and edge-centered tensor correlations. A continuous low-rank Gaussian decoder then reconstructs the density at arbitrary spatial coordinates while reusing atomic encodings independently of the evaluation grid. AIDEN achieves state-of-the-art accuracy on periodic
crystal benchmarks while remaining competitive for molecular systems, and further demonstrates zero-shot transferability across several structurally distinct out-of-distribution case studies. Furthermore, AIDEN provides substantially faster inference than both baseline models and full SCF calculations, enabling efficient charge density reconstruction for large-scale electronic structure calculations.
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All authors Yuxuan Zeng, Tong Xie, Taoyuze Lv, Zhicheng Zhong