Materials Science
A Transformer-based Model for Rapid Microstructure Inference from Four-Dimensional Scanning Transmission Electron Microscopy Data
Kwanghwi Je, Ellis R. Kennedy, Sungin Kim et al. (+2 more)
Properties of crystalline materials are closely linked to microstructure arising from the spatial arrangement, orientation, and phase of nanocrystals. Rapid characterization of crystalline microstructure can accelerate the identification of these links and the development of materials with desired properties. Here, we combine a machine learning framework with four-dimensional scanning transmission electron microscopy (4D-STEM) to enable fast inference of crystalline microstructure over large fields of view. The framework employs a
transformer-based architecture to predict crystallographic orientations and phases from 4D-STEM diffraction patterns, yielding spatially resolved maps of microstructural features at the nanoscale. With this framework, crystallographic orientations are inferred up to two orders of magnitude faster than widely used correlative template-matching approaches. This capability enables high-throughput characterization of complex crystalline materials and facilitates the establishment of structure-property relationships central to materials design and optimization.
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All authors Kwanghwi Je, Ellis R. Kennedy, Sungin Kim, Yao Yang, Erik H. Thiede
Strongly Correlated Electrons
Information lattice approach to the metal-insulator transition
William Skoglund, Elton Giacomelli, Yiqi Yang et al. (+2 more)
Correlation functions and correlation lengths are frequently used to describe phase transitions in
quantum systems, but they require an explicit choice of observables. The recently introduced information
lattice instead provides an observable-independent way to identify where and at which scale information is contained in
quantum lattice models. Here, we use it to study the difference between the metallic and insulating regime of one-dimensional noninteracting tight-binding chains. We find that the information per scale follows a power law in metals at low temperature and that Friedel-like oscillations are visible in the information
lattice. At high temperature or in
insulators at low temperature, the information per scale decays exponentially. Thus, the information
lattice is a useful tool for analyzing the metal-
insulator transition.
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All authors William Skoglund, Elton Giacomelli, Yiqi Yang, Jens H. Bardarson, Erik van Loon
Materials Science
Fan Yang, Rafael M. Fernandes and Turan Birol
Spin-orbit coupling (SOC) leads to splitting of otherwise
spin-degenerate bands in noncentrosymmetric materials, even if time-reversal
symmetry is present. While this gives rise to well-known phenomena such as the Rashba and Dresselhaus effects, various other terms are allowed based on the point group of the
crystal and the electronic
Hamiltonian. In this study, we utilize point group representations to illustrate that four different types of SOC terms (Rashba, Dresselhaus, Weyl, and Ising) can emerge in periodic solids. We construct reciprocal-space energy expressions for each type of SOC-induced splitting of opposite-
spin bands, and follow a similar procedure to also obtain minimal tight-binding models that capture all types of
spin-splittings for subgroups of two high-
symmetry groups $m\bar{3}m$ and $6/mmm$. Furthermore, we also obtain a complete list of nodal features in the electronic band structure in these systems, distinguishing between crystallographic-
symmetry-imposed nodal lines and those imposed by time-reversal-
symmetry only. Finally, we conclude by presenting a list of materials that host each type of inversion-breaking SOC effects. Our classification of the
spin-splitting
symmetries in non-
magnetic systems with SOC is the counterpart of the recent classification of
spin-splitting
symmetries in unconventional
magnetic systems without SOC, such as altermagnets and odd-parity magnets. More broadly, our work provides a basis for studying superconductivity and other collective electronic phenomena that are impacted by SOC-induced band splittings in noncentrosymmetric materials.
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Materials Science · Cross-listed from physics.chem-ph
Fast Generation of Pipek-Mezey Wannier Functions via the Co-Iterative Augmented Hessian Method
Gengzhi Yang and Hong-Zhou Ye
We report a $k$-point extension of the second-order co-iterative augmented Hessian (CIAH)
algorithm, termed $k$-CIAH, for Pipek-Mezey (PM) localization of Wannier functions (WFs). By exploiting an efficient evaluation of the Hessian-vector product, $k$-CIAH achieves $O(N_k^2 n^3)$ scaling in both CPU time and
memory, matching that of previously reported first-order $k$-space approaches while improving upon the $O(N_k^3 n^3)$ scaling of $\Gamma$-point CIAH, where $N_k$ denotes the number of $k$-points sampling the first Brillouin zone and $n$ characterizes the unit-
cell size.
Benchmark calculations on a diverse set of solids – including
insulators,
semiconductors, metals, and surfaces – demonstrate the fast and robust convergence of $k$-CIAH-based PMWF optimization, which yields an overall computational efficiency approximately 2-3–fold higher than first-order $k$-space methods and orders of magnitude higher than $\Gamma$-point CIAH for localizing 1000-5000 orbitals. The quality of the resulting PMWFs is further validated by accurate electronic band structures obtained via PMWF-based Wannier interpolation.
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Materials Science
Investigating the Electronic and Magnetic Properties of Na$_x$Fe$_{1/2}$Mn$_{1/2}$O$_2$ Cathode Materials with X-ray Compton Scattering
Veenavee Nipunika Kothalawala, Kosuke Suzuki, Johannes Nokelainen et al. (+21 more)
We discuss electronic and
magnetic properties of Na$_x$Fe$_{1/2}$Mn$_{1/2}$O$_2$, a promising Na-ion battery cathode material. Using x-ray Compton scattering, SQUID magnetometry, and density-functional-theory based modeling, we probe how electrons and
spins evolve during sodiation. By comparing Compton profiles of sodiated and desodiated samples, we show that oxygen 2$p$ orbitals drive the redox process, while transition-metal 3$d$ electrons become more delocalized, explaining the metallic phase at $x=2/3$. These profile differences define a quantitative descriptor for the sodiation range associated with improved conductivity. Electron holes on oxygen, reflected in oxygen magnetization, confirm the important role of oxygen in the electrochemical activity of the cathode.
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All authors Veenavee Nipunika Kothalawala, Kosuke Suzuki, Johannes Nokelainen, Ilja Makkonen, Erica West, Lassi Roininen, Jere Leinonen, Pekka Tynjälä, Petteri Laine, Juho Välikangas, Ulla Lassi, Assa Aravindh Sasikala Devi, Matti Alatalo, Yuki Mizuno, Naruki Tsuji, Hikaru Usami, Yuju Nagasaki, Tsuyoshi Takami, Yoshiharu Sakurai, Hiroshi Sakurai, Mohammad Babar, Venkat Vishwanathan, Arun Bansil, Bernardo Barbiellini
Soft Condensed Matter · Cross-listed from math.NA
A versatile FEM framework with native GPU scalability via globally-applied AD
Mohit Pundir, Flavio Lorez and David S. Kammer
Energy-based finite-element formulations provide a unified framework for describing complex physical systems in computational mechanics. In these energy-based methods, the governing equations can be obtained directly by considering the derivatives of a single global energy functional. While Automatic Differentiation (AD) can be used to automate the generation of these derivatives, current frameworks face a clear trade-off based primarily on the scale upon which the AD method is applied. Globally applied AD offers high expressivity but cannot currently be scaled to large problems. Locally applied AD scales well through traditional assembly methods, but the variety of physics and couplings that the framework can easily represent is more limited than the global approach. Here, we introduce an energy-centric framework tatva (https://github.com/smec-ethz/tatva) that defines the physics of a problem as a single global functional and applies AD globally to generate residual and tangent operators. By leveraging Jacobian-vector products for
matrix-free solvers and coloring-based sparse differentiation for materializing sparse tangent stiffness
matrices when needed, our flexible design scales linearly with the problem size on GPUs. We demonstrate that our framework can handle large problems (with millions of degrees of freedom) without
memory exhaustion. Additionally, it offers a unified, fully differentiable methodology that can address a wide range of problems, including multi-point constraints, mixed-dimensional coupling, and the incorporation of neural networks, while maintaining high performance and scalability on modern GPU architectures.
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Statistical Mechanics · Cross-listed from hep-th
Lifshitz critical points meet Zamolodchikov perturbation theory
António Antunes
Critical points of classical and
quantum lattice models are often described by scale-invariant Lifshitz theories which are anisotropic in the continuum limit, as characterized by a dynamical critical exponent $z\neq1$. This type of critical behavior can in principle be studied by deforming ordinary $z=1$ conformal field theories (CFTs) by relevant vector operators breaking the rotational/Lorentz
symmetry. In this short note, we consider a two-dimensional system of coupled minimal model CFTs $\mathcal{M}_{m,m+1}$ which realizes this perspective in a controlled fashion via Zamolodchikov's large $m$ expansion. The model turns out to exhibit interesting properties, including a
manifold of interacting Lifshitz fixed points and emergent rotational
symmetry in the infrared.
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Statistical Mechanics
Controlled Zeno-Induced Localization of Free Fermions in a Quasiperiodic Chain
Pinaki Singha, Nilanjan Roy, Marcin Szyniszewski et al. (+1 more)
We investigate measurement-induced localization in a continuously monitored one-dimensional Aubry–André–Harper model, focusing on the
quantum Zeno regime in which the measurements dominate coherent dynamics. The presence of a quasiperiodic potential renders the problem analytically tractable and enables a controlled study of the interplay between monitoring and disorder. We develop an analytical description based on an instantaneous Schrödinger equation with a measurement-induced effective potential constructed self-consistently from individual
quantum trajectories, without relying on postselection. In the
quantum Zeno regime, an emergent dominant energy scale reduces the problem to a transfer-
matrix formulation of an effective non-Hermitian
Hamiltonian, which allows direct computation of the Lyapunov exponent. Complementarily, we extract the localization length numerically from long-time steady-state
quantum state
diffusion trajectories by reconstructing the intrinsic localized single-particle wave functions and analyzing their spatial decay. These numerical results show quantitative agreement with the effective theory predictions, with controlled corrections of order $J^2/[\lambda^2+(\gamma/2)^2]$ (where $J$ is the hopping amplitude, $\gamma$ the measurement strength, and $\lambda$ the quasiperiodic potential). Our results underscore the connection between the effective non-Hermitian description and the
stochastic monitored dynamics, showing the interplay between Zeno-like localization, coherent hopping, and quasiperiodic-disorder-induced localization, while also laying the groundwork for understanding and exploiting measurement-induced localization as a tool for
quantum control and state preparation.
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All authors Pinaki Singha, Nilanjan Roy, Marcin Szyniszewski, Auditya Sharma
Strongly Correlated Electrons · Cross-listed from hep-th
Magic and Wormholes in the Sachdev-Ye-Kitaev Model
Valérie Bettaque and Brian Swingle
Any
quantum state is fully specified by the expectation values of a complete set of Hermitian operators. For a system of Majorana
fermions, such as the Sachdev-Ye-Kitaev (SYK) model, this set of observables can be taken to be all possible strings of Majorana
fermion operators. The expectation values of these
fermion strings in a thermal state depend erratically on the microscopic couplings that specify the SYK
Hamiltonian, and we study their statistical properties directly in the thermodynamic limit using path integral techniques. When the underlying SYK
Hamiltonian is chaotic, we find that these expectation values are well-modeled as real Gaussian random variables with zero mean and a variance that we compute. In contrast, for the integrable variant of SYK, we find that the expectation values are actually non-Gaussian. We then use these results to study measures of magic in the SYK thermal state, including the robustness of magic and the stabilizer Rényi
entropy. We also show that our results can be quantitatively reproduced with a dual
gravity calculation in the chaotic case at sufficiently low temperature. In this dual
gravity model the variance of a given microscopic operator string is related to a wormhole geometry stabilized by a massive particle which is dual to the operator string. Our results thus provide a concrete and quantitative setting in which to study the relationship between randomness, wormholes and closed universes, as well as a
holographic dual of
quantum magic.
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Strongly Correlated Electrons · Cross-listed from hep-th
Symmetric Gapped States and Symmetry-Enforced Gaplessness in 3-dimensions
Arun Debray, Matthew Yu and Weicheng Ye
We establish a comprehensive framework for characterizing the infrared (IR) phases of a fermionic
quantum theory in three spatial dimensions, based on its
quantum anomalies associated with a finite
symmetry. We uncover a fundamental dichotomy among these anomalies: the first class of anomalies can always be realized by symmetric gapped states, while the second class can never be realized by gapped states without breaking the given
symmetry, establishing the phenomenon of
symmetry-enforced gaplessness in these settings. Moreover, using the construction of
symmetry extension, we construct the candidate gapped states that theories with the first class of anomalies can flow to in the IR. As an application, we provide concrete predictions of the candidate IR phases of (3+1)-dimensional gauge theories based on our results. Our results also suggest that systems with discrete
chiral anomalies cannot be gapped out by adding arbitrary bosonic degrees of freedom.
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Strongly Correlated Electrons
Compact localized states and magnetic flux-driven topological phase transition in a diamond-dodecagon lattice geometry
Joydeep Majhi and Biplab Pal
We propose and investigate a novel two-dimensional (2D) tight-binding model defined on a diamond-dodecagon
lattice geometry that hosts multiple flat bands (FBs) and supports topological phase transitions driven by a
magnetic flux. This
lattice exhibits three completely flat, non-dispersive bands in the band structure in the absence of
magnetic flux due to destructive interference in the electron hoppings, leading to the emergence of compact localized states (CLS). These CLS are analytically constructed and exhibit real-space confinement of the electrons, arising solely due to the
lattice's geometrical frustration. It has been shown that these FBs are very robust against the introduction of weak random onsite disorder in the system. By tuning the uniform
magnetic flux threaded through the diamond plaquettes, we demonstrate a tunable
evolution of the band structure and show that certain bands develop nontrivial topological features with nonzero integer values of the Chern number. Additionally, we have computed the multi-terminal transport properties for this 2D
lattice system, which display the flux-tunable resonances and transmission suppression linked to the FBs, establishing a clear interplay between the localization,
topology, and transport. Our findings put forward the diamond-dodecagon
lattice as a robust and tunable platform for studying the flat-band physics and
magnetic flux-controlled topological phenomena, offering promising experimental feasibility in photonic
lattices and ultracold atomic systems.
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Quantum Gases
Observing dissipationless flow of an impurity in a strongly repulsive quantum fluid
Milena Horvath, Sudipta Dhar, Elisabeth Wybo et al. (+6 more)
The frictionless motion of an object through a fluid medium is commonly viewed as a hallmark of superfluidity. According to Landau, kinematic constraints prohibit superfluid behavior in one-dimensional (1D) bosonic systems. Here, using ultracold atoms, we show how a microscopic
impurity can propagate through a strongly interacting 1D Bose gas without any friction, at odds with conventional expectations. We inject the
impurity with initial velocities ranging from the subsonic to supersonic regime, and subsequently track its dynamics. For supersonic initial velocities, we observe the formation of a shock wave and a remarkably fast relaxation to a stationary regime, on a time scale that increases with decreasing
impurity velocity. After reaching the stationary state, the
impurity continues its motion through the system with a finite velocity. Our findings demonstrate how
quantum effects can conspire to eliminate dissipation of a microscopic object immersed in a
quantum fluid, thereby bringing novel insights into the propagation of matter and information in the
quantum realm.
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All authors Milena Horvath, Sudipta Dhar, Elisabeth Wybo, Dimitrios Trypogeorgos, Yanliang Guo, Mikhail Zvonarev, Michael Knap, Manuele Landini, Hanns-Christoph Nägerl
Materials Science · Cross-listed from physics.optics
Vision Transformer for Multi-Domain Phase Retrieval in Coherent Diffraction Imaging
Jialun Liu, David Yang and Ian Robinson
Bragg coherent diffraction imaging (BCDI) phase
retrieval becomes rapidly difficult in the strong-phase regime, where a
crystal contains distortions beyond half a
lattice spacing. An important special case is the phase domain problem, where blocks of a
crystal are displaced with sharp jumps at domain walls. The strong-phase, here defined as beyond $\pm \pi/2$, generates split Bragg peaks and dense fringe structure for which classical iterative solvers often stagnate or return different solutions from different initialisations. Here, we introduce an unsupervised
Fourier Vision Transformer (
Fourier ViT) to solve this block-phase, multi-domain phase-
retrieval problem directly from measured 2D Bragg diffraction intensities.
Fourier ViT couples reciprocal-space information globally through multiscale
Fourier token mixing, while shallow convolutional front and back-ends provide local filtering and reconstruction. We validate the approach on large-scale synthetic
datasets of Voronoi multi-domain
crystals with strong-phase contrast under realistic noise corruptions, and on experimental diffraction from a $\mathrm{La}_{2-x}\mathrm{Ca}_x\mathrm{MnO}_4$ nanocrystal. Across the regimes considered,
Fourier ViT achieves the lowest reciprocal-space mismatch ($\chi^2$) among the compared methods and preserves domain-resolved phase reconstructions for increasing numbers of domains. On experimental data, with the same real-space support,
Fourier ViT matches the iterative
benchmark $\chi^2$ while improving robustness to random initialisations, yielding a higher success rate of low-$\chi^2$ reconstructions than the complex convolutional neural network baseline.
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Materials Science
A Stochastic Cluster Expansion for Electronic Correlation in Large Systems
Annabelle Canestraight, Anthony J. Dominic, Andres Montoya-Castillo et al. (+2 more)
Accurate many-body treatments of condensed-phase systems are challenging because correlated solvers such as full configuration interaction (FCI) and the density
matrix renormalization group (DMRG) scale exponentially with system size. Downfolding and
embedding approaches mitigate this cost but typically require prior selection of a correlated subspace, which can be difficult to determine in heterogeneous or extended systems. Here, we introduce a
stochastic cluster expansion framework for efficiently recovering the total correlation energy of large systems with near-DMRG accuracy, without the need to select an active space a priori. By combining correlation contributions from randomly sampled environment orbitals with an exactly treated subspace of interest, the method reproduces total energies for non-reacting and reactive systems while drastically reducing computational cost. The approach also provides a quantitative diagnostic for molecule-solvent correlation, guiding principled
embedding decisions. This framework enables systematically improvable many-body calculations in extended systems, opening the door to high-accuracy studies of chemical processes in condensed phase environments.
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All authors Annabelle Canestraight, Anthony J. Dominic, Andres Montoya-Castillo, Libor Veis, Vojtech Vlcek
Mesoscale and Nanoscale Physics
Simultaneous High-Fidelity Readout and Strong Coupling for a Donor-Based Spin Qubit
Si Yan Koh, Weifan Wu, Kelvin Onggadinata et al. (+7 more)
Superconducting resonators coupled to solid-state
qubits offer a scalable architecture for long-range entangling operations and fast, high-fidelity readout. Realizing this requires low
photon-loss rates and
qubits with tunable electric dipole moments that couple strongly to the resonator's electric field while maintaining long coherence times. For
spin qubits,
spin-
photon coupling is typically achieved via
spin-charge hybridization. However, this introduces a fundamental trade-off: a large
spin-charge admixture enhances the coupling strength, which boosts readout and resonator-mediated gate speeds, but exposes the
qubit to increased decoherence, thereby increasing the threshold required for strong coupling and limiting the time available for accurate state measurement. This makes it essential to identify optimal operating points for each
qubit platform. We address this for the donor-based flip-flop
qubit, whose microwave-controllable electron-
nuclear spin states make it suitable for coupling to microwave resonators. We demonstrate that, by choosing intermediate tunnel couplings that balance strong interaction with long
qubit lifetimes, high-fidelity readout and strong coupling are simultaneously achievable. We also map out the respective charge-
photon couplings and
photon-loss rates required. Furthermore, we show that experimental constraints on charge-
photon coupling and
photon loss can be mitigated using squeezed input fields. As similar trade-offs appear in
quantum-dot-based
qubits, our methods and insights extend naturally to these platforms, offering a potential route toward scalable architectures.
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All authors Si Yan Koh, Weifan Wu, Kelvin Onggadinata, Arghya Maity, Mark Chiyuan Ma, Calvin Pei Yu Wong, Kuan Eng Johnson Goh, Bent Weber, Hui Khoon Ng, Teck Seng Koh
Other Condensed Matter · Cross-listed from cs.CE
MagneX: A High-Performance, GPU-Enabled, Data-Driven Micromagnetics Solver for Spintronics
Andy Nonaka, Yingheng Tang, Julian C. LePelch et al. (+7 more)
In order to comprehensively investigate the multiphysics coupling in spintronic devices, it is essential to parallelize and utilize GPU-acceleration to address the spatial and temporal disparities inherent in the relevant physics. Additionally, the use of cutting-edge time integration libraries as well as machine learning (ML) approaches to replace and potentially accelerate expensive computational routines are attractive capabilities to enhance modeling capabilities moving forward. Leveraging the Exascale Computing Project software framework AMReX, as well as SUNDIALS time-integration libraries and python-based ML workflows, we have developed an open-source micromagnetics modeling tool called MagneX. This tool incorporates various crucial
magnetic coupling mechanisms, including Zeeman coupling, demagnetization coupling, crystalline anisotropy interaction, exchange coupling, and Dzyaloshinskii-Moriya interaction (DMI) coupling. We demonstrate the GPU performance and scalability of the code and rigorously validate MagneX's functionality using the mumag standard problems and widely-accepted DMI
benchmarks. Furthermore, we demonstrate the data-driven capability of MagneX by replacing the computationally-expensive demagnetization physics with neural network libraries trained from our simulation data. With the capacity to explore complete physical interactions, this innovative approach offers a promising pathway to better understand and develop fully integrated spintronic and electronic systems.
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All authors Andy Nonaka, Yingheng Tang, Julian C. LePelch, Prabhat Kumar, Weiqun Zhang, Jorge A. Munoz, Christian Fernandez-Soria, Cesar Diaz, David J. Gardner, Zhi Jackie Yao
Strongly Correlated Electrons · Cross-listed from quant-ph
Non-Abelian Quantum Low-Density Parity Check Codes and Non-Clifford Operations from Gauging Logical Gates via Measurements
Maine Christos, Chiu Fan Bowen Lo, Vedika Khemani et al. (+1 more)
In this work, we introduce constructions for non-Abelian qLDPC codes obtained by gauging transversal Clifford gates using measurement and feedback. In particular, we identify two qualitatively different approaches to gauging qLDPC codes to obtain their non-Abelian counterparts. The first approach applies to codes that exhibit a generalized form of Poincaré duality and leads to a qLDPC non-Abelian Clifford stabilizer code, whose stabilizers are reminiscent of the action of a Type-III twisted
quantum double. Our second approach applies to general qLDPC codes, and uses a graph of ancilla
qubits which may be tailored to properties of the input codes to gauge a single transversal gate. For both constructions, the resulting gauged codes are shown to have properties analogous to 2D non-Abelian topological order – e.g. the analog of a single anyon on a
torus. We conclude by demonstrating that our gauging procedures enable magic state preparation via the measurement of logical Clifford gates. Consequently, our gauging constructions offer a protocol for performing non-Clifford operations on any qLDPC code.
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All authors Maine Christos, Chiu Fan Bowen Lo, Vedika Khemani, Rahul Sahay
Quantum Gases
Second excited state of ${}^4\mathrm{He}$ tetramer
A. Deltuva
The four-
boson universality suggests the existence of the second excited tetramer state in a system of cold ${}^4\mathrm{He}$ atoms. It is not bound but could be seen as a resonance in the atom-trimer scattering. This process is rigorously calculated using the momentum-space transition operator framework with two realistic interatomic potentials. The $S$-wave phase shift and cross section show a resonant behavior below the excited trimer threshold, but there are sizable nonresonant contributions from $P$ and $D$ waves as well. The position and width of the resonant state is determined, and for the latter significant finite-range effects are found.
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Materials Science
Kagome edge states under lattice termination, spin-orbit coupling, and magnetic order
Sajid Sekh, Annica M. Black-Schaffer and Andrzej Ptok
We study the edge state properties of a two-dimensional kagome
lattice using a tight-binding approach, focusing on the role of
lattice termination,
spin-orbit coupling, and
magnetic order. In the pristine limit, we show that the existence of localized edge states is highly sensitive to boundary geometry, with certain terminations completely suppressing edge modes. Kane-Mele
spin-orbit coupling opens a bulk gap and stabilizes topologically protected helical edge states, yielding a robust $\mathbb{Z}_2$ insulating phase that is insensitive to termination details. In contrast, the combined effect of a Zeeman field and Rashba
spin-orbit coupling drives the system into Chern insulating phases, with Chern numbers consistent with the number of
chiral edge modes. We further demonstrate that non-coplanar
magnetic textures generate multiple Chern phases through finite scalar
spin chirality, with Kane-Mele coupling strongly tuning the topological gaps. Our results provide important insights into the tunability of edge states in the kagome
lattice, which can be key to designing materials with novel electronic properties and topological phases.
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Statistical Mechanics · Cross-listed from quant-ph
A Route to Quantum-Coherent Thermodynamics
Maurizio Fagotti
Equilibrium thermodynamics emerges because a vast number of microscopic states become indistinguishable at the level of local observables. We start from the observation that a nonequilibrium
quantum state can also be represented by an ensemble of pure states that minimizes the average energy variance. We show that varying the statistical weights within this optimal family organizes state space into “minimum-variance leaves”, which generalize the space of stationary states underlying
equilibrium. We observe thermodynamic compression on the leaves, which in the simplest scenario manifests itself in the indistinguishability of states with the same energy density. We call this “leaf typicality”; at
equilibrium it reduces to eigenstate thermalization or its generalizations. Numerical tests support leaf typicality on some leaves and indicate a breakdown of its stronger forms on others, suggesting a rich thermodynamic organization beyond
equilibrium. These results open a route to a unified statistical mechanics of
equilibrium and nonequilibrium
quantum states.
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Statistical Mechanics
Charged moments and symmetry-resolved entanglement from Ballistic Fluctuation Theory
Giorgio Li, Léonce Dupays and Paola Ruggiero
The charged moments of a reduced density
matrix provide a natural starting point for deriving
symmetry-resolved Rényi and
entanglement entropies, which quantify how
entanglement is distributed among
symmetry sectors in the presence of a global internal
symmetry in a
quantum many-body system. In this work, we study charged moments within the framework of Ballistic Fluctuation Theory (BFT). This theory describes large-scale ballistic fluctuations of conserved charges and associated currents and, by exploiting the height-field formulation of twist fields, gives access to the asymptotic behaviour of their two-point correlation functions. In Del Vecchio Del Vecchio et al. $[1]$, this approach was applied to the special case of branch-point twist fields used to compute
entanglement entropies within the replica approach. Here, we extend those results by applying BFT to composite branch-point twist fields, obtained by inserting an additional gauge field. Focusing on free
fermions, we derive analytic expressions for charged Rényi
entropies both at
equilibrium, in generalized Gibbs ensembles, and out of
equilibrium following a
quantum quench from $U(1)$ preserving pair producing integrable initial states. In the latter case, our results agree with the
conjecture arising from the quasiparticle picture.
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Mesoscale and Nanoscale Physics · Cross-listed from physics.optics
Theoretical description of interface states in a tetragonal lattice of bianisotropic resonators
Alina D. Rozenblit and Nikita A. Olekhno
In the present paper, we construct a theoretical description of a three-dimensional photonic structure in the form of a tetragonal
lattice of bianisotropic resonators applying a dyadic Green's function approach. By representing the resonators as point electric and
magnetic dipoles, we obtain the Bloch
Hamiltonians for the approximations considering the interactions between the nearest, next-nearest, and next-to-next-nearest resonators, and construct the corresponding real-space tight-binding models. We analyze the band diagrams, spatial structure of the eigenmodes, and their localization, revealing quadratic degeneracies in the vicinity of high-
symmetry points in the absence of bianisotropy and the emergence of in-gap states localized at a domain wall upon the introduction of bianisotropy. Finally, we compare the theoretical results with full-wave numerical simulations for an array of bianisotropic resonators.
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Strongly Correlated Electrons
Magnetopological mechanics in Maxwell lattice frustrated Mott insulators
Hong-Hao Song, Pengwei Zhao and Gang v. Chen
Topological boundary modes, a hallmark of
quantum topological phases, remarkably occur in classical mechanical systems through an interesting correspondence with the
quantum case. Here, we explore the Maxwell
lattice frustrated Mott
insulators and argue that the combination of the intrinsic
spin-
lattice coupling and the
spin exchanges could induce the topological mechanics with topological boundary floppy modes in the
phonon spectra. This mechanism and phenomena are dubbed
magnetic topological mechanics, or, magnetopological mechanics in short. Focusing on a two-dimensional kagomé
lattice spin model, we illustrate how strong
spin-
lattice coupling drives a spontaneous
lattice distortion, resulting in the topological Maxwell
lattice with the topological polarization and non-trivial
phonon spectra. Moreover, the
magnetic field, that directly changes the
spin state, indirectly influences the
lattice structure via the
spin-
lattice coupling, thereby providing a method to control the Maxwell
lattice and the boundary modes. We expect this work to inspire interests in the Maxwell
lattice Mott insulating materials and the coupling between
lattices and electronic orders.
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Quantum Gases
Protocols for a many-body phase microscope: From coherences and d-wave superconductivity to Green's functions
Christof Weitenberg, Luca Asteria, Ola Carlsson et al. (+2 more)
Quantum gas microscopes probe
quantum many-body
lattice states via projective measurements in the occupation basis, enabling access to various density and
spin correlations. Phase information, however, cannot be directly obtained in these setups. Recent experiments went beyond this by measuring local current operators and local phase fluctuations. Here we propose how
Fourier-space manipulation in a matter-wave microscope allows access to various long-range off-diagonal correlators in experimentally realistic settings, realizing a many-body phase microscope. We demonstrate in particular how the fermionic d-wave superconducting order parameter in arbitrary Hubbard-type models, the non-equal time Green's function yielding the spectral function, or the hidden order of composite
bosons in a fractional Chern
insulator can be directly measured. Our results show the great potential of matter-wave microscopy for accessing exotic correlators including phases and coherences and characterizing intriguing
quantum many-body states.
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All authors Christof Weitenberg, Luca Asteria, Ola Carlsson, Annabelle Bohrdt, Fabian Grusdt
Strongly Correlated Electrons
Huge Symmetric Elastoresistance in the Kondo Lattice YbRh$_2$Si$_2$
Soumendra Nath Panja, Jacques G. Pontanel, Julian Kaiser et al. (+2 more)
Heavy-
fermion metals are prototype correlated electron systems for the study of Kondo
entanglement and
quantum criticality. We use the
symmetry decomposed elastoresistance to uncover the fingerprints of strain-dependent Kondo scattering as function of temperature and
magnetic field in the prototypical tetragonal Kondo
lattice YbRh$_2$Si$_2$. By combining longitudinal and transverse resistance measurements under uniaxial strain applied along the tetragonal $[100]$ and $[110]$ directions, we obtain the elastoresistive responses in the in plane $A_{1g}$, $B_{1g}$, and $B_{2g}$
symmetry channels. While the responses in the
symmetry-breaking channels are negligible, a huge enhancement of the isotropic symmetric $A_{1g}$ elastoresistance is found approaching -50 at low temperatures. Scaling analysis and comparison with linear thermal expansion measurements reveal that the symmetric elastoresistance probes the contribution of Kondo scattering to the strain dependence of
magnetic entropy and signals strain- and field controlled
quantum criticality upon cooling to 2 K.
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All authors Soumendra Nath Panja, Jacques G. Pontanel, Julian Kaiser, Anton Jesche, Philipp Gegenwart
Materials Science
A critical assessment of bonding descriptors for predicting materials properties
Aakash Ashok Naik, Nidal Dhamrait, Katharina Ueltzen et al. (+4 more)
Most machine learning models for materials science rely on descriptors based on materials compositions and structures, even though the chemical bond has been proven to be a valuable concept for predicting materials properties. Over the years, various theoretical frameworks have been developed to characterize bonding in solid-state materials. However, integrating bonding information from these frameworks into machine learning pipelines at scale has been limited by the lack of a systematically generated and validated database. Recent advances in high-throughput bonding analysis workflows have addressed this issue, and our previously computed
Quantum-Chemical Bonding Database for Solid-State Materials was extended to include approximately 13,000 materials. This database is then used to derive a new set of
quantum-chemical bonding descriptors. A systematic assessment is performed using statistical significance tests to evaluate how the inclusion of these descriptors influences the performance of machine-learning models that otherwise rely solely on structure- and composition-derived features. Models are built to predict elastic, vibrational, and thermodynamic properties typically associated with chemical bonding in materials. The results demonstrate that incorporating
quantum-chemical bonding descriptors not only improves predictive performance but also helps identify intuitive expressions for properties such as the projected force constant and
lattice thermal conductivity via symbolic regression.
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All authors Aakash Ashok Naik, Nidal Dhamrait, Katharina Ueltzen, Christina Ertural, Philipp Benner, Gian-Marco Rignanese, Janine George
Soft Condensed Matter
Solvothermal vapor annealing and environmental control setup with adjustable magnetic field module for GISAXS studies
Christian Kjeldbjerg, Bo Jakobsen, Miriam Varón et al. (+3 more)
A compact, modular environmental control and solvothermal vapor annealing chamber designed for maintaining a controlled atmosphere with regard to solvent humidity and temperature is presented. The setup allows ex situ and in situ grazing incidence small-angle X-ray scattering (GISAXS) investigations of thin film self-assembly and reorganization. Its modular slotting system enables stable reconfiguration, including the integration of an adjustable
magnetic field module. The temperature is maintained via a water-based heating and cooling loop supplemented by resistive elements, and the solvent vapor environment is regulated using a commercial controlled mixing and evaporation unit. The performance of the setup is validated through measurements of fill and quench times together with
magnetic field mapping with Gauss meter measurements and finite element simulations. Further, the versatility of the setup is demonstrated with four research examples using the chamber for solvothermal vapor annealing of block copolymer thin films together with lab-based ex situ and in situ GISAXS measurements. The portable new design offers robust environmental control and flexibility for advanced thin film investigations both in the lab and at large scale facilities. The design can be adapted for grazing incidence small-angle
neutron scattering, GISANS.
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All authors Christian Kjeldbjerg, Bo Jakobsen, Miriam Varón, Kim Lefmann, Cathrine Frandsen, Dorthe Posselt
Strongly Correlated Electrons · Cross-listed from hep-th
Refined half-integer condition on RG flows
Ken Kikuchi
Renormalization group flows are constrained by
symmetries. Traditionally, we have made the most of 't Hooft anomalies associated to the
symmetries. The anomaly is mathematically part of the data for the monoidal structure on
symmetry categories. The
symmetry categories sometimes admit additional structures such as braiding. It was found that the additional structures give further constraints on renormalization group flows. One of these constraints is the half-integer condition. The condition claims the following. Braidings are characterized by conformal dimensions. A
symmetry object $c$ in a braided
symmetry category surviving all along the flow thus has two conformal dimensions, one in ultraviolet $h_c^\text{UV}$ and the other in infrared $h_c^\text{IR}$. In a renormalization group flow with a renormalization group defect, they add up to a half-integer $h_c^\text{UV}+h_c^\text{IR}\in\frac12\mathbb Z$. We find a necessary condition for the sum to be half-integer. We solve some flows with the refined half-integer condition.
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Quantum Gases
Two-photon-assisted collisions in ultracold gases of polar molecules II : Optical shielding of ultracold polar molecular collisions
Gohar Hovhannesyan, Charbel Karam, Romain Vexiau et al. (+4 more)
We theoretically investigate the collisions between ultracold polar molecules in the presence of two
lasers ensuring a Raman resonant transition on individual molecules to suppress
photon scattering, taking the example of bosonic $^{23}$Na$^{39}$K molecules. By varying
laser detunings and intensities, we enable a repulsive long-range interaction potential between molecules. After solving a set of coupled Schrödinger equations with the
Hamiltonian written in the basis of
laser-dressed states of the molecule pair at infinite distance, we identify quasi-resonant conditions under which elastic collisions are favored over inelastic and reactive ones, by a factor of about 2, thus demonstrating a promising pathway for efficient two-
photon optical shielding of ultracold molecular collisions. The results are analyzed in terms of scattering length of the colliding
laser-dressed molecules, which exhibit prominent resonances assigned to the interaction of the entrance channel with other specific channels, consistent with the existence of a quasi-bound level of the long-range molecular pair induced by the
lasers.
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All authors Gohar Hovhannesyan, Charbel Karam, Romain Vexiau, Leon Karpa, Maxence Lepers, Nadia Bouloufa-Maafa, Olivier Dulieu
Materials Science
Stacking theory for bilayer two-dimensional magnets
Jun-Xi Du, Sike Zeng and Yu-Jun Zhao
Two-dimensional unconventional magnetism has recently attracted growing interest due to its intriguing physical properties and promising applications in spintronics. However, existing studies on stacking-induced unconventional magnetism mainly focus on specific materials and stacking configurations. Here, we develop a general
symmetry-based stacking theory for two-dimensional magnets. We first introduce
spin layer groups as the fundamental
symmetry framework, providing the essential
magnetic symmetry information for the stacking theory. Based on this framework, we construct the complete set of 448 collinear
spin layer groups for describing two-dimensional collinear magnets. Subsequently, we develop a general
magnetic stacking theory applicable to arbitrary
magnetic systems and derive its general solutions. Using CrF$_3$ as an illustrative example, we show how this theory enables designs of two-dimensional unconventional magnetism, as validated by first-principles calculations. We realize two-dimensional fully compensated ferrimagnetism through our stacking theory. Our work provides a general
symmetry-guided platform for discovering and designing stacking-induced unconventional magnetism.
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