Materials Science · Cross-listed from physics.comp-ph
Discovery of Hyperelastic Constitutive Laws from Experimental Data with EUCLID
Arefeh Abbasi, Maurizio Ricci, Pietro Carrara et al. (+4 more)
We assess the performance of EUCLID, Efficient Unsupervised Constitutive Law Identification and Discovery, a recently proposed framework for automated discovery of constitutive laws, on experimental data. Mechanical tests are performed on natural rubber specimens spanning simple to complex geometries, from which we collect both global, force elongation, and local, full-field displacement, measurements. Using these data, we obtain constitutive laws via two routes, the conventional identification of unknown parameters in a priori selected material models, and EUCLID, which automates model selection and parameter identification within a unified model-discovery pipeline. We compare the two methodologies using global versus local data, analyze predictive accuracy, and examine generalization to unseen geometries. Moreover, we quantify the experimental noise, investigate the coverage of the material state space achieved by each approach and discuss the relative performance of different
datasets and different a priori chosen models versus EUCLID.
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All authors Arefeh Abbasi, Maurizio Ricci, Pietro Carrara, Moritz Flaschel, Siddhant Kumar, Sonia Marfia, Laura De Lorenzis
Materials Science · Cross-listed from physics.app-ph
A novel approach to modelling the properties of HEMTs operating in the saturation region
Kaiyuan Zhao, Guangfen Yao, Xiaoyu Cheng et al. (+3 more)
Currently, the ASM-HEMT model, QPZD model and EPFL model are all based on the three-terminal potential as the core, and relate the electrical characteristics such as I-V and C-V to Vd, Vs and Vg, so as to accurately build the HEMT model with high accuracy and fast convergence. However, there has not yet been a model based on three-terminal potentials that can quickly model the velocity saturation effect as well as the carrier concentration distribution and the electric field distribution inside the HEMT, which makes the existing models have to rely on a number of empirical parameters in the modelling process, which lacks the actual physical significance. In previous publications, models for the electric field, carrier concentration distribution based on the effective length of the gate were presented. In this paper, the model proposed in previous publications is improved to enable: (1) the calculation of the current Ids without relying on the Newton iterative method with fast simulation convergence behavior; (2) The Vdsat when the HEMT reaches saturation at different Vgo is redefined instead of using Vdsat = Vgo; (3) The expression of the v-E relationship is redefined relying on the different transport of carriers, which solves the problem of the large model error of the electric field distribution in the region below the gate, and makes the model's accuracy of the I-V characteristic further improved. The model was validated by characterising the I-V and E-V of the HEMT through TCAD simulation with RMSE below 5%.
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All authors Kaiyuan Zhao, Guangfen Yao, Xiaoyu Cheng, Luqiao Yin, Kailin Ren, Jianhua Zhang
Superconductivity · Cross-listed from nucl-ex
First non-zero measurement of a nuclear electric dipole moment
Gary Prézeau
This paper reports the first non-zero measurement of a
nuclear electric dipole moment using a novel method based on the rate of change of a supercurrent first proposed in 2016~\cite{https://doi.org/10.48550/arxiv.1604.02152} and fleshed out in this current paper. The theory, experimental concept and implementation are described in detail. The non-zero
nuclear electric dipole moment measured with over 1000 hours of data was that of $^{181}$Ta producing a best value $|d_\text{e}^\text{Ta}|=(3.39\pm0.31_\text{stat})\cdot10^{-32}e\cdot\text{cm}$ and $|d_\text{e}^\text{Ta}|=(3.39\pm3.18)\cdot10^{-32}e\cdot\text{cm}>0$ at 99.985%CL. There is an uncertainty on the value of overall multiplicative parameters such as the self-inductance of the superconducting
circuit ($\pm4\%$), the mutual inductance between the SQUID pickup coil and the sample wire ($\pm15\%$), and the magnitude of the solenoid current ($\pm5\%$). An upper-limit was estimated for the control element, $^{207}$Pb, $|d_\text{e}^\text{Pb}|\lesssim1.2\cdot10^{-31}e\cdot\text{cm}$ at 95%CL.
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Materials Science · Cross-listed from physics.flu-dyn
Water wave scattering by a surface-mounted rectangular anisotropic elastic plate
Ben Wilks, Michael H. Meylan, Zachary J. Wegert et al. (+2 more)
This paper considers the problem of water wave scattering by a rectangular anisotropic elastic plate mounted on the ocean surface, with either free, clamped or simply-supported edges. The problem is obtained as an expansion over the dry modes of the elastic plate, which are computed using a Rayleigh–Ritz method. In turn, the component diffraction and radiation problems are solved by formulating a boundary integral equation and solving numerically using a constant panel method. The results are presented to highlight the resonant responses of the plate under different forcing scenarios. In particular, we illustrate how the excitation of certain modes can be forbidden due to
symmetry.
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All authors Ben Wilks, Michael H. Meylan, Zachary J. Wegert, Vivien J. Challis, Ngamta Thamwattana
Mesoscale and Nanoscale Physics
Near-field radiative heat transfer in the dual nanoscale regime between polaritonic membranes
Livia Correa McCormack, Lei Tang and Mathieu Francoeur
The enhancement and attenuation of near-field radiative heat transfer between polaritonic SiC, SiN and SiO2 subwavelength membranes is analyzed. Fluctuational electrodynamics simulations combined with a modal analysis show that all membranes support corner and edge modes, which can induce a large 5.1-fold enhancement for SiC and a 2.1-fold attenuation for SiO2 of the heat transfer coefficient with respect to that between infinite surfaces. The enhancement or attenuation is directly related to material losses which reduce the density of available electromagnetic states between the membranes.
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Mesoscale and Nanoscale Physics
Intrinsic Maximum Light Absorption in Laser-Field-Driven Growth of Highly Ordered Silicon Nanowire Arrays
Jin Qin and Zhikun Liu
We provide direct experimental evidence for a state-selection principle in a far-from-
equilibrium system. Using the
laser-driven growth of silicon nanowires as a uniquely clean and quantifiable platform, we show that a long-range ordered array emerges as the system spontaneously selects the periodicity that maximizes its collective light absorption. This establishes a direct, measurable link between a maximum dissipation/absorption principle and emergent structural order. Our results thus offer a concrete test for models of non-
equilibrium self-organization.
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Statistical Mechanics · Cross-listed from quant-ph
Open-system dynamics in local Lindbladians with chaotic spectra
Sanket Chirame and Fiona J. Burnell
We investigate the physical consequences of having a spectrum that satisfies random
matrix theory (RMT) for generic Lindbladians, and compare its implications for spatially local and completely random Lindblad dynamics in one spatial dimension. We find that Lindbladians whose spectrum is described by RMT exhibit quasiuniversal early-time dynamics for quantities nonlinear in the density
matrix, in the sense that for generic, highly entangled initial states, the early time
evolution is independent of the choice of initial state. We numerically investigate how locality generically imposes constraints on the size-dependence of Lindblad eigenoperators. This size dependence implies that linear observables, such as expectation values of local operators, are highly sensitive to eigenmodes outside the bulk of the spectrum in the thermodynamic limit, and plays a central role in limiting operator growth in the presence of dissipation. We find that when single-site dissipation dominates, an operator's decoherence scales approximately linearly with its Pauli weight, even in the presence of two-site jump operators. When two-site only dissipation dominates, however, this generic trend in operator size can be violated for numerically accessible system sizes, leading to long-lived high Pauli-weight operators.
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Materials Science · Cross-listed from physics.optics
Visible Imaging of Incoherent 1200-nm Light via Triplet–Triplet Annihilation Upconversion
Pournima Narayanan, Rabeeya Hamid, Linda Pucurimay et al. (+13 more)
Upconversion of low-energy
photons to higher-energy
photons provides an opportunity to surpass traditional limitations in fields such as 3D printing, photovoltaics, and photocatalysis. Triplet–triplet annihilation upconversion (TTA-UC) is particularly appealing for such applications as it can efficiently upconvert low-intensity, incoherent light. However, previously demonstrated thin-film TTA systems are simultaneously constrained by modest efficiencies and limited reach into the near infrared (NIR). Here, we design a single-layer thin-film bulk heterojunction that integrates PbS
quantum dots (QDs) as tunable NIR absorbers within an organic
semiconductor matrix of TES-ADT, achieving large anti-Stokes shifts up to 500 nm and high internal
quantum efficiencies across the NIR-I and NIR-II windows (800-1200 nm). Through the incorporation of 5-tetracene carboxylic acid ligands on the PbS QD surface, the yield of sensitized triplets was boosted, as confirmed by transient absorption and time-resolved photoluminescence measurements. The resulting films demonstrated a 15-fold improvement in UC efficiency. Furthermore, we demonstrate visible imaging of incoherent 1200 nm light via thin-film TTA-UC at incident intensities at the imaging mask as low as 20 mWcm$^2$, marking a significant advance toward practical implementation of solid-state NIR-to-visible upconversion.
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All authors Pournima Narayanan, Rabeeya Hamid, Linda Pucurimay, Ona Segura Lecina, Ben P. Carwithen, Jacob Schopp, Justin S. Edwards, Oluwaseun Noah Adeyeye, Demeng Feng, Diptarka Hait, Todd J. Martinez, Timothy W. Schmidt, Michael P. Nielsen, Murad J. Y. Tayebjee, Mikhail A. Kats, Daniel N. Congreve
Superconductivity · Cross-listed from quant-ph
Superconducting Gap Engineering in Tantalum-Alloy-Based Resonators
Chen Yang, Faranak Bahrami, Guangming Cheng et al. (+7 more)
Utilizing tantalum (Ta) in superconducting
circuits has led to significant improvements, such as high
qubit lifetimes and quality factors in both
qubits and resonators, underscoring the importance of material optimization in
quantum device performance. In this work, we explore superconducting gap engineering in Ta-based devices as a strategy to expand the range of viable host materials. By alloying 20 atomic percent hafnium (Hf) into Ta thin films, we achieve a superconducting transition temperature ($T_c$) of 6.09~K, as measured by DC transport, reflecting an increased superconducting gap. We systematically vary deposition conditions to control film orientation and transport properties of the Ta-Hf
alloy films. The enhancement in $T_c$ is further confirmed by microwave measurements at millikelvin temperatures. Despite the 40% increase in $T_c$ relative to pure Ta, the loss contributions from two-level systems (TLS) and quasiparticles (QPs) remain unchanged in the low-temperature regime. These findings highlight the potential of material engineering to improve superconducting
circuit performance and motivate further exploration of engineered
alloys for
quantum technologies.
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All authors Chen Yang, Faranak Bahrami, Guangming Cheng, Mayer Feldman, Nana Shumiya, Stephen A. Lyon, Nan Yao, Andrew A. Houck, Nathalie P. de Leon, Robert J. Cava
Mesoscale and Nanoscale Physics · Cross-listed from physics.chem-ph
Helical orbitals in electrical uni-directional molecular motors
Štěpán Marek, Wulf Wulfhekel, Ferdinand Evers et al. (+1 more)
The generation of unidirectional motion has been a long-standing challenge in engineering of molecular motors. Here, a mechanism driving the rotation is presented based on electron current through helical orbitals on a $\pi$-bonded carbon chain. Such electron current through helical orbitals has been shown to be circulating around the carbon chain. It is natural to expect that the associated electronic angular momentum drives a rotation when the current is turned on. As intuitive as this relation might seem, it is also incomplete because a formal definition of helicality in terms of a physical observable has not yet been given. Such a definition is proposed here. Based on this definition, we show how helicality determines the motor's sense of rotation. We exemplify the relation between helicality and angular momentum in Hückel models of linear carbon chains (cumulenes and oligoynes). We attribute the previously reported opposite helicality sense of frontier orbitals (HOMO and LUMO) to the approximate sub-
lattice symmetry. For oligoynes, this
symmetry is hidden in the sense that it does not reduce to a mere labeling of atoms. Sub-
lattice symmetry, combined with time-reversal invariance, allows us to derive Onsager-type reciprocal relations of various linear response coefficients, dictating e.g. an odd energy dependence of angular momentum response to voltage bias. We propose an observable consequence of the approximate sub-
lattice symmetry: If the carbon chain is employed as an axle of a molecular rotor, the sense of rotation is independent on the direction of the current.
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All authors Štěpán Marek, Wulf Wulfhekel, Ferdinand Evers, Richard Korytár
Materials Science
Development and Validation of Interatomic Potential for Sc and Al-Sc Alloys: Thermodynamics, Solidification, and Intermetallic Ordering
Avik Mahata
We present a second-nearest-neighbor Modified Embedded Atom Method (2NN–MEAM) potential for Scandium (Sc) and Aluminum-Scandium (Al–Sc)
alloys that unifies cohesive, thermodynamic, and solidification behavior within a single transferable framework. The Sc component accurately reproduces cohesive energy,
lattice constants, defect energetics, and the experimental melting point obtained from two-phase coexistence, demonstrating reliable description of both hcp and
liquid phases. The Al–Sc binary interaction parameters were fitted using the L1$_2$–Al$_3$Sc reference and benchmarked against first-principles and calorimetric data. The potential reproduces the strong negative formation enthalpy of Al$_3$Sc (–0.45~eV~atom$^{-1}$), correct relative stability of competing phases, and realistic elastic properties. Mixing enthalpies of the
liquid alloy agree with ideal-associated-solution and CALPHAD models, confirming that the potential captures exothermic Al–Sc association in the melt. Molecular-dynamics simulations of solidification reveal the expected temperature and composition dependence of homogeneous nucleation. Pure Al crystallizes readily, while Al–1~at.%~Sc exhibits a longer incubation and slower growth at the same absolute temperature due to reduced undercooling and solute drag. Within the
alloy, ordered Al$_3$Sc-type L1$_2$ embryos appear spontaneously, with Sc atoms occupying cube-corner (B) sites surrounded by twelve Al neighbors. Energy–volume trajectories confirm that the potential links thermodynamics to microstructural
evolution. Overall, the developed 2NN–MEAM potential provides a quantitatively grounded basis for modeling melting, solidification, and intermetallic ordering in Sc and Al–Sc systems, enabling future multicomponent
alloy design and large-scale nucleation studies.
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Materials Science
Advancing AI-Driven Analysis in X-ray Absorption Spectroscopy: Spectral Domain Mapping and Universal Models
Nina Cao, Pavan Ravindra, Shubha R. Kharel et al. (+6 more)
In recent years, rapid progress has been made in developing artificial intelligence (AI) and machine learning (ML) methods for x-ray absorption spectroscopy (XAS) analysis. Compared to traditional XAS analysis methods, AI/ML approaches offer dramatic improvements in efficiency and help eliminate human bias. To advance this field, we advocate an AI-driven XAS analysis pipeline that features several inter-connected key building blocks:
benchmarks, workflows, databases, and AI/ML models. Specifically, we present two case studies for XAS ML. In the first study, we demonstrate the importance of reconciling the discrepancies between simulation and experiment using spectral domain mapping (SDM). Our ML model, which is trained solely on simulated spectra, predicts an incorrect oxidation state trend for Ti atoms in a combinatorial zinc titanate film. After transforming the experimental spectra into a simulation-like representation using SDM, the same model successfully recovers the correct oxidation state trend. In the second study, we explore the development of universal XAS ML models that are trained on the entire periodic table, which enables them to leverage common trends across elements. Looking ahead, we envision that an AI-driven pipeline can unlock the potential of real-time XAS analysis to accelerate scientific discovery.
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All authors Nina Cao, Pavan Ravindra, Shubha R. Kharel, Chuntian Cao, Boyang Li, Xuance Jiang, Matthew R. Carbone, Xiaohui Qu, Deyu Lu
Strongly Correlated Electrons
Three Types of Non-Fermi-Liquid Fixed Point for a Triplet Quantum Impurity in a Cubic Metal
Anna I. Tóth
In cubic metals, a local,
magnetic moment with a triplet ground state coupled to $\Gamma_8$ conduction electrons can give rise to various non-
Fermi liquid (NFL)
quantum critical behaviors. To date, only those exchange couplings have been studied that are spherically symmetric already in the high-temperature, local moment regime. Namely, only the effects of potential scattering, dipolar
spin exchange, i.e. Kondo, and quadrupolar exchange couplings were considered, and two types of NFL fixed points have been identified. However, in cubic
symmetry, six independent exchange couplings can be present in the
Hamiltonian: in addition to the spherically symmetric potential scattering and Kondo exchange, there are four independent, spherical-
symmetry-breaking
Hamiltonian terms: two quadrupolar-quadrupolar, a dipolar-octupolar and a quadrupolar-octupolar exchange interaction, where the first/second element of the compound adjectives refers to the
impurity/conduction-electron transitions. While all of them flow to fixed points where rotational invariance is recovered, I found that one of the quadrupolar-quadrupolar couplings flows to a previously unidentified NFL fixed point. I derive the exchange couplings allowed by cubic
symmetry, solve them with the numerical renormalization group, and present three types of NFL excitation spectrum$-$one of which is novel, at least in the context of a
quantum impurity with a triplet ground state.
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Strongly Correlated Electrons
Four-Spin Interactions as a Route to Multiple-Q Topological Magnetic Order
Kazuki Okigami and Satoru Hayami
We investigate the role of four-
spin interactions in stabilizing exotic multiple-$Q$ topological
spin textures and demonstrate their ability to realize a skyrmion
crystal. While such higher-order interactions are known to be important, their intricate nature makes systematic model construction significantly challenging. To address this issue, we develop a theoretical framework that connects microscopic real-space four-
spin couplings to their effective interactions in momentum space, providing a clear route to engineer target
magnetic phases. Applying this framework to a frustrated Heisenberg model with designed four-
spin interactions, we identify the stabilization of the zero-field skyrmion
crystal with a topological number of two via simulated annealing. Furthermore, our momentum-space analysis reveals the intrinsic mechanism by which the well-known ring-exchange interaction also favors the skyrmion
crystal. Our findings not only present a concrete model for a higher-order skyrmion
crystal but also offer a general methodology for understanding and designing a wide range of complex multiple-$Q$
magnetic orders driven by multi-
spin interactions.
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Materials Science
Morphotropic Phase Boundary (MPB) Induced Enhancement of Ferroelectric and Piezoelectric Properties in Li and Ta modified K0.5Na0.5NbO3
Satyaranjan Sahoo, Dhiren K. Pradhan, Shalini Kumari et al. (+9 more)
Lead-free (K0.48Na0.48Li0.04)(Nb1-xTax)O3 (KNLNT-x) ceramics were synthesized to study the effects of Li and Ta substitution on phase transition behavior, microstructure, and ferroelectric, dielectric, and piezoelectric properties. X-ray diffraction and Raman spectroscopy show that compositions with x < 0.10 exhibit a single orthorhombic (Amm2) phase, while 0.10 <= x <= 0.20 show coexistence of orthorhombic and tetragonal (Amm2 + P4mm) phases. For x > 0.20, a single tetragonal (P4mm) phase is obtained. Microstructural analysis shows a dense ceramic with decreasing grain size as Ta concentration increases. Temperature-dependent dielectric studies reveal two transitions: orthorhombic-tetragonal (TO-T) and tetragonal-cubic (TC). Both transition temperatures decrease systematically with increasing Ta, and TO-T shifts below room temperature for x > 0.15. The composition KNLNT-0.20 exhibits the highest dielectric constant (Er = 556) and piezoelectric coefficient (d33 = 159 pC/N). The enhanced piezoelectric response is attributed to a morphotropic phase boundary rather than a shift of the polymorphic phase boundary temperature. A composition-temperature phase diagram was constructed based on XRD, Raman, and dielectric data.
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All authors Satyaranjan Sahoo, Dhiren K. Pradhan, Shalini Kumari, Abhisikta Sahu, Koyal Suman Samantaray, Vikas N. Thakur, Anupam Mishra, M. M. Rahaman, Ashok Kumar, Reji Thomas, Philip D. Rack, Dillip K. Pradhan
Statistical Mechanics
Cluster percolation and dynamical scaling in the Baxter–Wu model
Alexandros Vasilopoulos, Michail Akritidis, Nikolaos G. Fytas et al. (+1 more)
We investigate the percolation behavior of Fortuin-Kasteleyn–type clusters in the
spin-$1/2$ Baxter–Wu model with three-
spin interactions on a triangular
lattice. The considered clusters are constructed by randomly freezing one of the three sublattices, resulting in effective pairwise interactions among the remaining
spins. Using Monte Carlo simulations combined with a finite-size scaling analysis, we determine the percolation temperature of these
stochastic clusters and show that it coincides with the exact thermal critical point of the model. The critical exponents derived from cluster observables are consistent with those of the underlying thermal phase transition. Finally, we analyze the dynamical scaling of the multi-cluster and single-cluster
algorithms resulting from the cluster construction, highlighting their efficiency and scaling behavior with system size.
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All authors Alexandros Vasilopoulos, Michail Akritidis, Nikolaos G. Fytas, Martin Weigel
Strongly Correlated Electrons
When Wannier centers jump: Critical points between atomic insulating phases
Yunchao Zhang and T. Senthil
We study a class of
quantum phase transitions between featureless bosonic atomic
insulators in $(2+1)$ dimensions, where each phase exhibits neither topological order nor protected edge modes. Despite their lack of
topology, these
insulators may be “obstructed” in the sense that their Wannier centers are not pinned to the physical atomic sites. These
insulators represent distinct phases, as no
symmetry-preserving adiabatic path connects them. Surprisingly, we find that for certain
lattices, the critical point between these
insulators can host a conformally invariant state described by
quantum electrodynamics in $(2+1)$ dimensions (QED$_3$). The emergent electrodynamics at the critical point can be stabilized if the
embedding of the microscopic
lattice symmetries suppresses the proliferation of monopoles, suggesting that even transitions between trivial phases can harbor rich and unexpected physics. We analyze the mechanism behind this phenomenon, discuss its stability against perturbations, and explore the
embedding of
lattice symmetries into the continuum through anomaly matching. In all the models we analyze, we confirm that the QED$_3$ is indeed emergeable, in the sense that it is realizable from a local
lattice Hamiltonian.
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Soft Condensed Matter
Active Ionic Fluxes Induce Symmetry Breaking in Charge-Patterned Nanochannels
Sergi G. Leyva, Ahis Shresta and Monica Olvera de la Cruz
Biological systems rely on autonomous modes of charge transport to transmit signals. Instead, conventional synthetic systems typically depend on external fields, such as voltage or pressure gradients, to induce transport, which limits their applicability. Here, we investigate nanochannels in which an electrolyte is confined by symmetric boundary patterns combining surface charge and active ionic fluxes. We show that the interplay between
diffusion, electrostatics, and hydrodynamics in such nano-confined active-charged systems can trigger
symmetry breaking above a critical active flux, leading to directed flow. Our results suggest that active-charged nanochannels can generate net flows of the order of hundreds of millimeters per second, opening pathways toward adaptable ionic devices and neuromorphic architectures.
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Materials Science
Unusual dependence on the angle of magnetic field for the spin Hall magnetoresistance of monodomain epitaxial BiFeO3 thin films
Yongjian Tang, Pratap Pal, Matthew Roddy et al. (+7 more)
Spin Hall magnetoresistance (SMR) measurements provide a way to probe the surface
spin structure of insulating
magnetic materials. Such measurements produce resistance signals of the form {$\Delta$}R {$\propto$} cos[2($\alpha$-$\alpha$$_0$)], where $\alpha$ is the angle between the current and the external in-plane
magnetic field. Previous experiments on a wide range of materials have found $\alpha$$_0$ = 0$\deg$ for ferromagnets and $\alpha$$_0$ = 90$\deg$ for antiferromagnets. Here we investigate SMR in
bilayers of Pt with monodomain BiFeO$_3$ multiferroic epitaxial thin films. We observe signals of the form {$\Delta$}R {$\propto$} cos[2($\alpha$-$\alpha$$_0$)] but surprisingly the angle $\alpha$$_0$ can take values very different from 90$\deg$ or 0$\deg$, with large variations from sample to sample. The aim of the paper is to report this striking departure from the expected
magnetic field dependence of SMR and to encourage consideration of possible microscopic mechanisms.
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All authors Yongjian Tang, Pratap Pal, Matthew Roddy, Jon Schad, Ruofan Li, Joongwon Lee, Farhan Rana, Tianxiang Nan, Chang-Beom Eom, Daniel C. Ralph
Strongly Correlated Electrons
Robust Orbital-Selective Flat Bands in Transition-Metal Oxychlorides
Xiangyu Luo, Ludovica Zullo, Sahaj Patel et al. (+10 more)
Flat electronic bands, which amplify electron correlations by quenching kinetic energy, provide an ideal foundation for exotic
quantum phases. However, prevailing strategies – including geometrically frustrated
lattices, moire superlattices and heavy-
fermion physics – suffer from inherent trade-offs among robustness, tunability and orbital selectivity, limiting their broad applicability. Here, we unveil an intrinsic orbital-selective flat-band mechanism in the van der Waals materials NbOCl2 and TaOCl2, directly observed by angle-resolved photoemission spectroscopy (ARPES) and understood through density functional theory (DFT) and Wannier analysis. Crucially, we experimentally demonstrate that this momentum-independent flat band exhibits remarkable robustness, surviving from the bulk
crystal down to the few-layer limit at room temperature. Our theoretical analysis traces its origin to the hybridization between Nb-dz2 orbital chains and the Lieb-like dx2-y2 sublattice, which is further reinforced by Peierls dimerization. Our findings not only establish transition-metal oxychlorides as a robust and tunable platform for flat-band-driven correlated phases under ambient conditions, but also uncover a new orbital-selective design principle for realizing flat bands in
quantum materials.
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All authors Xiangyu Luo, Ludovica Zullo, Sahaj Patel, Dongjin Oh, Qian Song, Asish K. Kundu, Anil Rajapitamahuni, Elio Vescovo, Natalia Olszowska, Rafal Kurleto, Dawid Wutke, Giorgio Sangiovanni, Riccardo Comin
Superconductivity
Superconductivity suppression and bilayer decoupling in Pr substituted YBa$_2$Cu$_3$O$_{7-\delta}$
Jinming Yang, Zheting Jin, Siqi Wang et al. (+17 more)
The mechanism behind superconductivity suppression induced by Pr substitutions in YBa$_2$Cu$_3$O$_{7-\delta}$ (YBCO) has been a mystery since its discovery: in spite of being isovalent to Y$^{3+}$ with a small
magnetic moment, it is the only rare-earth element that has a dramatic impact on YBCO's superconducting properties. Using angle-resolved photoemission spectroscopy (ARPES) and DFT+$U$ calculations, we uncover how Pr substitution modifies the low-energy electronic structure of YBCO. Contrary to the prevailing Fehrenbacher-Rice (FR) and Liechtenstein-Mazin (LM) models, the low energy electronic structure contains no signature of any $f$-electron hybridization or new states. Yet, strong electron doping is observed primarily on the antibonding
Fermi surface. Meanwhile, we reveal major electronic structure modifications to Cu-derived states with increasing Pr substitution: a pronounced CuO$_2$
bilayer decoupling and an enhanced CuO chain hopping, implying indirect electron-release pathways beyond simple 4$f$ state ionization. Our results challenge the long-standing FR/LM mechanism and establish Pr substituted YBCO as a potential platform for exploring correlation-driven phenomena in coupled 1D-2D systems.
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All authors Jinming Yang, Zheting Jin, Siqi Wang, Camilla Moir, Mingyu Xu, Brandon Gunn, Xian Du, Zhibo Kang, Keke Feng, Makoto Hashimoto, Donghui Lu, Jessica McChesney, Martin Sundermann, Hlynur Gretarsson, Shize Yang, Wei-Wei Xie, Alex Frano, Sohrab Ismail-Beigi, M. Brian Maple, Yu He
Statistical Mechanics
Mrinal Kanti Sarkar, Saranyo Moitra and Rajdeep Sensarma
We show that odd order Rényi
entropies $S^{(2q+1)}$ of a system of interacting scalar fields can be calculated as the free energy of $2q+1$ replicas of the system with additional quadratic inter-replica couplings in the subsystem at the time of measurement of the
entropy. These couplings replace boundary field matching conditions. This formalism works both in and out of thermal
equilibrium, for closed as well as open
quantum systems, and provides a general dictionary between measurable correlation functions and
entanglement entropy. $S^{(2q+1)}$ can be analytically continued to calculate the von Neumann
entropy $S^{\mathrm{vN}}$. We provide an exact formula relating $S^{(2q+1)}$ and $S^{\mathrm{vN}}$ with correlation functions in a non-interacting theory. For interacting theories, we provide rules for constructing all possible Feynman diagrams for $S^{(2q+1)}$. We show that the boundary matching conditions cannot be completely eliminated while calculating Rényi
entropies of even order due to presence of zero modes in replica space.
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Strongly Correlated Electrons
Reconstructing Spin Hamiltonians of 2D Gutzwiller-Projected Wavefunctions
Lucas Z. Brito and J. B. Marston
We apply the correlation
matrix Hamiltonian reconstruction technique to the two-dimensional Gutzwiller-projected
Fermi sea and {\pi}-flux states on finite-sized square and triangular
lattices. Our results indicate no
spin Hamiltonian with simple local interaction terms stabilizes such states for finite system sizes. We develop a quantitative assessment of the importance of local interactions to the stabilization of these
liquid states. Lastly, we systematically assess arguments for the origin of local terms driving a Gutzwiller-projected ground state.
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Disordered Systems and Neural Networks · Cross-listed from quant-ph
Adiabatic transport of neural network quantum states
Matija Medvidović, Alev Orfi, Juan Carrasquilla et al. (+1 more)
Variational methods have offered controllable and powerful tools for capturing many-body
quantum physics for decades. The recent introduction of expressive neural network
quantum states has enabled the accurate representation of a broad class of complex wavefunctions for many
Hamiltonians of interest. We introduce a first-principles method for building neural network representations of many-body excited states by adiabatically continuing eigenstates of simple
Hamiltonians into the strongly correlated regime. With controlled access to the full many-body gap, we obtain accurate estimates of critical exponents. Successive eigenstate estimates can be run entirely in parallel, enabling precise targeting of excited-state properties without reference to the rest of the spectrum, opening the door to large-scale numerical investigations of universal properties of entire phases of matter.
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All authors Matija Medvidović, Alev Orfi, Juan Carrasquilla, Dries Sels
Mesoscale and Nanoscale Physics
Topological Order Without Band Topology in Moiré Graphene
Hui Liu, Raul Perea-Causin, Zhao Liu et al. (+1 more)
The discovery of zero-field fractional Chern
insulators (FCIs) in moiré materials has attracted intense interest in the interplay between
topology and correlations. Here, we demonstrate that fractionalized topological order can emerge under realistic conditions even within a topologically trivial moiré band. By projecting long-range Coulomb interactions into a trivial band of twisted multilayer
graphene, we identify a set of incompressible FCI ground states exhibiting fractional quantized
Hall conductance. Their Laughlin-like behavior is further confirmed through the particle-cut
entanglement spectrum. We trace the origin of this phase to the strongly inhomogeneous distribution of
quantum geometry within the moiré Brillouin zone, which reshapes interaction effects independently of the band
topology. Extending this heuristic
quantum geometric mechanism, we demonstrate that similarly unexpected Laughlin-like FCIs can also be stabilized in higher-Chern-number moiré bands under experimentally accessible conditions. Our results establish realistic scenarios under which many-body topological order can emerge independently of single-particle band
topology.
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All authors Hui Liu, Raul Perea-Causin, Zhao Liu, Emil J. Bergholtz
Quantum Gases · Cross-listed from hep-ph
Adiabatic hydrodynamization and quasinormal modes of nonthermal attractors
Matisse De Lescluze, Michal P. Heller, Aleksas Mazeliauskas et al. (+2 more)
Nonthermal attractors govern the emergent self-similar dynamics of far-from-
equilibrium quantum systems, from ultrarelativistic
nuclear collisions to cold-atom experiments. Within the framework of adiabatic hydrodynamization, the approach to a nonthermal attractor is described by the decay of excited states of an effective
Hamiltonian. Using an exactly solvable kinetic theory – the longitudinally expanding, overoccupied
gluon plasma dominated by small-angle elastic scattering – we establish a direct correspondence between the eigenmodes of adiabatic hydrodynamization and the quasinormal mode spectrum of the nonthermal attractor. This equivalence suggests a general framework for identifying universal dynamical structures in nonequilibrium systems. As a byproduct, we derive analytic prescaling solutions for strongly longitudinally expanding systems.
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All authors Matisse De Lescluze, Michal P. Heller, Aleksas Mazeliauskas, Bruno Scheihing-Hitschfeld, Clemens Werthmann
Strongly Correlated Electrons
A universal description of Mott insulators: Characterizing quantum phases beyond broken symmetries
Matheus de Sousa, Zhiyu Fan and Wei Ku
Using Mott
insulators as a prototypical example, we demonstrate a dynamics-based characterization of
quantum phases of matter through a general N-body renormalization group framework. The essential "Mott-ness" turns out to be characterized by a change of size-scaling of the effective intra- momentum repulsions between long-lived emergent "eigen-particles" that encodes the dynamics of two-body bound states in the high-energy sector. This directly offers a universal characterization at long space-time scale for the corresponding class of Mott
insulators through a uniform single occupation of all momenta, and otherwise Mott metals. This universal description naturally paves the way to topological Mott
insulators and is straightforward to extend to bosonic Mott systems. More generally, this demonstration exemplifies a generic paradigm of characterizing
quantum phases of matter through their distinct dynamics beyond broken
symmetries.
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Mesoscale and Nanoscale Physics
Skyrmion behavior in attractive-repulsive square array of pinning centers
L. Basseto, N. P. Vizarim, J. C. Bellizotti Souza et al. (+1 more)
We investigate the driven dynamics of a single skyrmion in a square
lattice of mixed pinning sites, where attractive and repulsive defects coexist using a particle-based model. The mixed landscape yields directional locking at $\theta_{\rm sk}=-45^\circ$ and flow at locked angles near the intrinsic skyrmion
Hall angle. By mapping defect strengths, we show that weaker attraction lowers the depinning threshold, whereas stronger repulsion stabilizes and broadens the $-45^\circ$ locking plateau. Moreover, combinations of attractive and repulsive defect strengths allows control of directional lockings and their force ranges. Defect size further tunes the response, selecting among $-45^\circ$, $-50^\circ$, $-55^\circ$, and $\approx-59^\circ$. These results establish mixed pinning as a practical knob to steer skyrmion trajectories and the effective
Hall response, providing design guidelines for skyrmion-based
memory and logic devices.
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All authors L. Basseto, N. P. Vizarim, J. C. Bellizotti Souza, P. A. Venegas
Mesoscale and Nanoscale Physics
Electric field controlled second-order anomalous Hall effect in altermagnets
Arnob Mukherjee, Biplab Sanyal, Annica M. Black-Schaffer et al. (+1 more)
Altermagnets are a recently discovered class of compensated magnets with momentum-dependent
spin splittings and unusual transport properties, even without a net magnetization. In the presence of combined four-fold rotation and time-reversal ($C_4\mathcal{T}$)
symmetry, linear and also second-order, driven by a Berry
curvature dipole, anomalous
Hall responses are forbidden in any pure $d$-wave altermagnet. Nevertheless, here we find that the nontrivial
quantum metric of the occupied Bloch states allows for an electric field induced Berry
curvature dipole, which generates a strong and tunable second-order
Hall current, enabling it to be switched on or off by simply adjusting the relative orientation between the
symmetry-reducing dc field and the ac probe field. Specifically, we investigate the electric field induced second-order anomalous
Hall response in a two-dimensional Rashba-coupled hybrid altermagnet that interpolates between $d_{x^2-y^2}$ ($B_{1g}$) and $d_{xy}$ ($B_{2g}$) altermagnet
symmetry, motivated by recent proposals for mixed-
symmetry states. Crucially, the nonlinear signal is highly sensitive to the underlying
symmetry of the altermagnetic order at specific doping levels, offering a purely electrical method to distinguish distinct altermagnetic orders. Our results position hybrid altermagnets as a promising platform for controllable nonlinear transport and spintronic applications.
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All authors Arnob Mukherjee, Biplab Sanyal, Annica M. Black-Schaffer, Ankita Bhattacharya