Soft Condensed Matter
Resonances in Overdamped Odd Materials
Julius Kiln and Alexander Mietke
Odd viscoelasticity arises in parity-violating nonequilibrium materials, where it leads to unconventional mechanical responses and oscillatory relaxation even in overdamped systems. While many living and active
chiral materials present promising candidates to exhibit odd viscoelasticity, there is currently no approach that allows for a rheological inference of the large number of elastic and viscous
moduli that even a minimal isotropic odd viscoelastic material can depend on. Generalizing the century-old Papkovich-Neuber ansatz to active materials, our work introduces an odd Papkovich-Neuber (OPN) solution – an analytic solution for any isotropic linear odd fluid or solid, each described by up to 6 independent
moduli – that enable us to study the boundary-driven response in geometries that mimic common rheology methods. OPN solutions reveal three physically distinct resonances in odd viscoelastic solids that are characteristic of the underlying material
moduli and can all be interpreted within a single
geometric framework. Underlying this unification is an equivalent description of overdamped odd viscoelastic materials in terms of damped harmonic oscillators. Resonances appear as the effective damping coefficients of these oscillators vanish, which is facilitated by the activity that powers odd material properties.
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Statistical Mechanics
Streaming Molecular Dynamics Simulation Data for On-the-fly Processing and Analysis
Amruthesh Thirumalaiswamy, Lawson J. Woods, Heekun Cho et al. (+6 more)
Only a small fraction of the data generated in state-of-the-art all-atom multi-microsecond molecular dynamics (MD) simulations is typically analyzed. With femtosecond integration steps, microsecond simulations generate billions of time steps containing atomic positions, velocities, and forces, often corresponding to petabytes of data. Since this exceeds practical storage capacities, only a subset of frames is usually written to trajectory files at intervals of 10-100 ps. While sufficient for ensemble averages and slow dynamics, this approach discards information on fast processes such as molecular vibrations, solvent dynamics, short-lived transition states, and transport phenomena that are directly related to macroscopic properties and experimental observables. Here, we introduce a streaming framework for MD simulations that provides direct access to all data generated during a running simulation. Instead of writing high-frequency output to disk, the framework enables user-defined analysis and processing routines to access simulation data in real time. To achieve this, we extend the Interactive Molecular Dynamics (IMD) protocol and implement an enhanced version, termed IMDv3, in the MD packages GROMACS, NAMD, and LAMMPS. We further introduce the Python package imdclient, which receives IMDv3 data streams and exposes them to external applications. To maximize usability, we add an imdclient-based reader to the MDAnalysis package, enabling streamed simulation data to be analyzed alongside conventional trajectory files.
Benchmark results show that streaming can improve performance compared to simulations with high-frequency trajectory output. Example applications include live monitoring of custom variables, evaluation of velocity time-correlation functions with fast fluctuations, and real-time analysis of membrane pore currents.
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All authors Amruthesh Thirumalaiswamy, Lawson J. Woods, Heekun Cho, Hugo MacDermott-Opeskin, Jennifer Clark, Irfan Alibay, Yuxuan Zhuang, Oliver Beckstein, Matthias Heyden
Statistical Mechanics
Resonant interactions in the $\alpha$-FPUT lattice with site-dependent coefficients
Lorenzo Migliorelli, Giovanni Dematteis, Sergio Chibbaro et al. (+1 more)
The wave
turbulence framework has proven to be an effective tool for analyzing certain features of nonlinear energy transfer in one-dimensional nonlinear chains. In this work, we extend this approach to the $\alpha$-FPUT problem when the spring stiffness $\chi$ and the nonlinear coefficient $\alpha$ are site-dependent. Although three-wave interactions are non-resonant for constant coefficients, their spatial modulation gives rise to a non-trivial resonant
manifold. In this framework, we derive a new kinetic equation that suggests the possibility of substantially faster thermalization with respect to the constant coefficient case. The new kinetic equation includes also an extra term that can be associated to the Bragg-scattering mechanism, which promotes the isotropization of the wave-action spectral density function. We corroborate these results with direct numerical simulations, confirming the radically faster thermalization pathway in the presence of random coefficients.
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All authors Lorenzo Migliorelli, Giovanni Dematteis, Sergio Chibbaro, Miguel Onorato
Materials Science
ChatMOSP: A Chemistry-Grounded Mobile Agent for Working-State Catalyst Simulations
Sanyang Ye, Rui Qi, Beien Zhu et al. (+1 more)
Catalytic nanoparticles restructure dynamically under reaction conditions, so their working morphology and activity are governed by temperature, pressure, and gas composition. However, converting experimentally specified environments into physically meaningful morphology-performance simulations remains difficult because the translation of reaction conditions into model-specific energetic, kinetic, and execution parameters requires the specialized knowledge in computational catalysis. Here we report ChatMOSP, a chemistry-grounded mobile scientific
agent that translates natural-
language and voice-expressed catalytic requests into parameter-validated simulations using the Multi-scale Operando Simulation Package. ChatMOSP maps catalyst identity, temperature, pressure, gas composition, and target observables onto multiscale structure reconstruction and kinetic Monte Carlo tasks, retrieves database parameters or constructs missing inputs from an online literature-
retrieval workflow, and executes validated MOSP workflows. Using CO oxidation on Pd nanoparticles as an example, we verify the ChatMOSP simulations capture the temperature-induced transition from faceted to rounded morphologies observed by in-situ TEM experiments either by built-in database or from web-retrieved literature information when the parameters are absent. Moreover, we demonstrate the capability of ChatMOSP to perform end-to-end study at mobile devices to simulate a pressure-coverage-morphology-activity feedback cycle for Pt CO oxidation to interpret the oscillatory CO conversion. These results establish ChatMOSP as a physically constrained mobile
agent for accessible and interpretable catalyst working-state simulations.
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All authors Sanyang Ye, Rui Qi, Beien Zhu, Yi Gao
Materials Science
The structure of a melt: The case of liquid bismuth
Flor B. Quiroga, Isaías Rodríguez, David Hinojosa et al. (+3 more)
Molecular Dynamics (MD) is performed on supercells of 216 atoms of bismuth, going from 300 K to 573 K in 100 steps and maintaining it in the
liquid state, at 573 K, during 500 steps using the Materials Studio (MS) suite of codes. The Pair Distribution Functions (PDFs) and the Plane Angle Distributions (PADs) of the last 1, 10, 25 and 100 steps of the MD have been obtained. Averaging the last 100 steps, as representative of the
liquid, Reverse Monte Carlo (RMC) was applied to obtain 4 atomic structures, one for each set of initial random velocities. Then, a detailed structural study of
liquid bismuth at 573 K was undertaken; PDFs and PADs are calculated and reported. Two noticeable peaks appear for the PDFs, at 3.25 and 6.55 Å, along with a pseudo peak (shoulder) at 4.6 Å. This shoulder (after the first peak) of the PDFs is found to be related to the third and fourth neighbor peaks of the crystalline Wyckoff structure and also to the diagonal distances in deformed squares in the
liquid structure. For completeness J(r)s are also reported. Two prominent peaks in the MS PADs are observed: 53{\deg} and 85{\deg}; and two for the RMC PADs: 58{\deg} and 90{\deg}, suggesting the existence of deformed triangles and squares. Less abundant are higher-order geometrical structures.
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All authors Flor B. Quiroga, Isaías Rodríguez, David Hinojosa, Alexander Valladares, Renela M. Valladares, Ariel A. Valladares
Materials Science
AB2X4 spinel structures: similarity and difference between the centrosymmetric, Fd-3m, and non-centrosymmetric, F4132, space groups
Alla Arakcheeva, Arnaud Magrez and Gervais Chapuis
Many compounds belonging to the spinel AB2X4 structure play an important role due to their wide range of practical applications. Most of them are traditionally assigned to the centrosymmetric space group Fd-3m. However, the physical properties of some spinels are incompatible with centrosymmetry. This discrepancy is often accounted for by reducing the
symmetry to the non-centrosymmetric space group F-43m, allowing thus small atomic displacements from their original position in Fd-3m. In this work, we demonstrate that the loss of the inversion
symmetry can occur without any atomic displacements, since the centrosymmetric Fd-3m and non-centrosymmetric F4132 space groups are equivalent for structure determination and refinement based on X-ray diffraction data. If consistent with experiment, only the use of an anharmonic model of atomic displacements can distinguish these space groups. This study aims to clarify certain misconceptions regarding the structural
symmetry and physical properties of spinel type compounds.
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Mesoscale and Nanoscale Physics
Quantized thermal current vortices
Ferenc Márkus and Katalin Gambár
The thermal
Hall effect has emerged as a fundamental tool for probing exotic quasiparticles and topological order, particularly in
magnetic insulators where electronic conduction is suppressed. Much like skyrmions, which are characterized by their topologically protected
spin configurations, the thermal
Hall effect is deeply rooted in the
geometric properties of the underlying physical space. Although the effect is a well-established experimental phenomenon, current research points toward the existence of its
quantum analogue: the quantized thermal
Hall effect. In this paper, we provide a theoretical framework for this
quantum version based on Sommerfeld's flux quantization. Furthermore, we demonstrate the potential existence of dissipationless thermal current
vortices. We suggest that these
vortices may play a crucial role in the stability and dynamics of other topological structures, such as skyrmion
lattices, offering a new perspective on the interplay between heat transport and
magnetic textures.
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Strongly Correlated Electrons
Charge density wave in a band insulator
Md Shafayat Hossain, Wenhao Liu, Yuqi Zhang et al. (+20 more)
Charge density wave (CDW) implies a periodic modulation of the charge density. Typically observed in metallic systems, CDWs arise from
Fermi surface instabilities, resulting in the total or partial gapping of the
Fermi surface. Here, we present experimental evidence for a CDW state emerging in a band
insulator which has no
Fermi surface. The bulk and surface of our material platform, Bi4Br4, is gapped over the entire Brillouin zone. Through topographic and spectroscopic imaging at low temperatures, we unveil an unexpected unidirectional charge modulation in Bi4Br4, breaking the
lattice translation
symmetry. The CDW develops at temperatures below 40 K and adds an energy gap atop the existing insulating gap of Bi4Br4. Furthermore, our transport measurements reveal nonlinear electrical conduction, a phenomenon conventionally associated with the sliding or phason mode of incommensurate CDWs. These highly unusual observations represent a new type of CDW and demand a new theoretical framework for CDWs.
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All authors Md Shafayat Hossain, Wenhao Liu, Yuqi Zhang, Qi Zhang, Chao Lei, Nana Shumiya, Kouta Dagnino, Maksim Litskevich, Yu-Xiao Jiang, Jia-Xin Yin, Nikhil Dhale, Zi-Jia Cheng, Byunghoon Kim, Yongkai Li, Tyler A. Cochran, Xian P. Yang, Fan Zhang, Yugui Yao, Zhiwei Wang, Bing Lv, Titus Neupert, Luis Balicas, M. Zahid Hasan
Strongly Correlated Electrons
Signature of spin liquid state in a frustrated 3D antiferromagnet
Satish Kumar, U. Jena, A. Bandhopadhay et al. (+4 more)
Frustrated pyrochlore
lattices in transition-metal
oxides provide an ideal platform for realizing exotic
quantum states, including
spin liquids with unconventional low-energy excitations arising from the macroscopic ground-state degeneracy of corner-sharing tetrahedral networks. Here, we report the synthesis and comprehensive characterization of ZnCrGaO$4$, a frustrated three-dimensional pyrochlore-like magnet in which intrinsic cation ordering gives rise to unavoidable atomic-site disorder. A Curie–Weiss analysis of the high-temperature
magnetic susceptibility yields a large negative Curie–Weiss temperature, $\theta{\mathrm{CW}} \approx -205$ K, indicating dominant
antiferromagnetic exchange interactions ($J/k_{\mathrm{B}} \sim 55$ K) between Cr$^{3+}$ ($S = 3/2$) moments. Despite the presence of strong
antiferromagnetic interactions, no signature of long-range
magnetic ordering is observed down to 125 mK, as evidenced by specific-heat and ac-susceptibility measurements. Furthermore, the absence of bifurcation between zero-field-cooled and field-cooled dc
magnetic susceptibilities measured at 0.01 T indicates the absence of
spin freezing, which is further supported by the frequency-independent ac susceptibility down to 250 mK. The presence of broad maxima in the
magnetic specific heat and ac susceptibility at low temperatures suggests the development of short-range
spin correlations within a dynamic
magnetic state. In addition, the low-temperature specific heat follows a power-law behavior below 1 K, indicating the presence of unconventional low-energy excitations and algebraic
spin correlations. These results provide compelling evidence for a dynamic correlated ground state in ZnCrGaO$_4$, establishing it as a promising platform for exploring highly frustrated $S > 1/2$ three-dimensional
quantum magnets and potential
spin-
liquid behavior.
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All authors Satish Kumar, U. Jena, A. Bandhopadhay, G. B. G. Stenning, D. T. Adroja, S. Petit, P. Khuntia
Disordered Systems and Neural Networks
Anderson Localization: A Floquet operator Krylov space perspective
Hsiu-Chung Yeh and Aditi Mitra
The problem of Anderson localization, as well as the single particle localization-delocalizaton transition of the Aubry-André model, is studied employing operator Krylov space methods. It is shown that even when the dynamics is generated by a
Hamiltonian, studying the dynamics at stroboscopic rather than continuous times has its advantages. In particular, mapping the dynamics to an effective Floquet problem results in an operator Krylov space description where quantities such as the spectral function can be computed with fewer computational resources, while a moment method exists that allows for the extraction of Krylov parameters directly from the discrete time autocorrelation function. For stroboscopic dynamics, the operator Krylov space corresponds to the dynamics of an edge operator of an inhomogeneous Floquet transverse field Ising model, with the parameters of this effective model generated recursively. The Krylov parameters show disorder-averaged renormalization with their distribution narrowing as the recursion step increases. It is shown that a more physical spectral function is obtained from the Krylov parameters obtained from the disorder-averaged autocorrelation function, rather than the disorder-averaged Krylov parameters. The delocalized (localized) phase is shown to correspond to the appearance (absence) of a Porter-Thomas distribution, a ballistically propagating (localized) wavefront in operator Krylov space, and a smooth (discrete) Berstein-Szegö power-spectrum. The localization-delocalization transition is also demonstrated in operator Krylov space. A Porter-Thomas distribution is also observed at the critical point. The long-time dynamics and the inverse participation ratio at the critical point is shown to exhibit behavior consistent with a multi-fractal scaling with system size.
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Statistical Mechanics
Theory of supercooled water
Jacobo Troncoso and Claudio A. Cerdeiriña
We introduce a model of water contemplating true supercooled-
liquid states that, as such, are metastable with respect to the crystalline-solid ones. Its numerical solutions reproduce from Speedy-Angell's stability-limit picture to Poole et al.'s metastable
liquid–
liquid criticality. The real existence of a
liquid–
liquid critical point is found to gain significant theoretical plausibility from a hitherto unnoticed analogy with the “inversion thermodynamics” of Joule-Thomson gas throttling process and, by extension, with the equivalent phenomenology exhibited by black holes.
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Disordered Systems and Neural Networks · Cross-listed from quant-ph
Dynamical self-dual criticality in Fibonacci-monitored quantum Ising chains
Finn Eckstein, Harald Schmid, Quinten Preiss et al. (+3 more)
For the
quantum phase transition in the transverse-field Ising chain, Kramers-Wannier duality not only protects its critical properties but also pinpoints the location of the phase transition. Its role in out-of-
equilibrium, monitored dynamics, however, remains largely unexplored beyond time-periodic Floquet protocols where self-duality turns into a statistical average
symmetry. Here we explore the emergence of dynamical self-duality in the absence of time-translation
symmetry by investigating the monitored dynamics of one-dimensional Ising/Majorana chains where measurements are arranged in a quasiperiodic Fibonacci sequence. We find that the dynamical extension of this non-invertible
symmetry to an out-of-
equilibrium setting allows one to organize the dynamical phase diagram of entangled phases, both predicting the transition locations and protecting universal critical behavior. Analytically and numerically, we identify two distinct critical lines, both related to the golden ratio, for Born-rule weak measurements and for random Clifford projective measurements. The latter coincides with the transition of a pure imaginary-time
evolution, which can be viewed as a post-selected trajectory. The universality classes of the long-time critical steady states at Fibonacci times are determined, while the transient dynamics between Fibonacci times is deformed by measurements, realizing dynamical measurement-altered
quantum criticality in real time.
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All authors Finn Eckstein, Harald Schmid, Quinten Preiss, Simon Trebst, Felix von Oppen, Guo-Yi Zhu
Mesoscale and Nanoscale Physics
Electrostatically stabilized surface flat bands in rhombohedral graphite at zero displacement field
Kryštof Kolář, Andrea F. Young and Cyprian Lewandowski
Rhombohedral (ABC-stacked) multilayer
graphene hosts interaction-driven phases enabled by surface flat bands at large displacement fields. In thick flakes, however, strong screening suppresses internal electric fields, raising the question of whether a flat-band regime is accessible within the same experimental paradigm. Here, we show that self-consistent, nonlinear electrostatics provides a robust alternative mechanism: even in the absence of a displacement field, a nonuniform near-surface potential flattens the surface-band dispersion and enhances the density of states. In the strong-coupling limit, electrostatics drives the system toward uniform half-filling at each momentum, yielding an asymptotically flat surface band without any gating. At realistic interaction strengths, surface-band flatness is tuned by the proximal gate, with maximal flatness achieved at hole doping when the band is empty. Combining analytic arguments with fully self-consistent calculations in a realistic model, we map the resulting low-field regime and connect to finite $N\!\sim\! 6-15$ layered samples, providing a framework for analyzing the
symmetry-broken phases observed in these systems. Our results motivate future experiments in large-$N$ devices and establish a low-field regime for exploring electrostatically induced flat-band physics.
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Mesoscale and Nanoscale Physics
Controlling spin-$\frac 12$ antiferromagnetic interaction strength in nanographene dimers
Robiatul Adawia, Pawel Tecmer and Pawel Potasz
We demonstrate that the effective
spin-exchange coupling $J$ in open-shell nanographene dimers can be precisely tuned via tip-induced dehydrogenation of selected carbon atoms. Using the double ionization potential equation-of-motion coupled-cluster singles and doubles (DIP-EOM-CCSD) method, we accurately compute the singlet-triplet gaps, which correspond directly to the exchange coupling $J$. We show that the position of the dehydrogenated (or hydrogen-passivated) site in triangulene dimers strongly modulates the singlet-triplet splitting, allowing $J$ to be tuned over a wide range - from a few meV to several tens of meV. This strategy provides a simple yet powerful route for designing tailored
spin models with alternating or spatially patterned
spin-exchange couplings.
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Quantum Gases
Pressure and Size Dependence of Roton Emission and Vortex Creation by Moving Objects in He~II in $T \to 0$ Limit: Generalized Nonlocal Gross-Pitaevskii Model
Nicolás Pablo Müller, Ladislav Skrbek, Yuri A. Sergeev et al. (+1 more)
In the framework of generalized, nonlocal Gross-Pitaevskii (GP) model, we study numerically the pressure- and size-dependent mechanisms of roton emission and
vortex nucleation by objects moving in superfluid $^4$He. As far as the authors are aware, this is the first attempt to analyze the pressure dependence of these mechanisms and the associated critical velocities within a single theoretical framework. For each of several pressures in the range from 0 to the solidification pressure of $\approx25$~bar, we chose the parameters of the interatomic interaction potential such that the resulting excitation spectrum for the generalized, nonlocal GP equation approximates fairly accurately the pressure-dependent dispersion curve determined experimentally by Godfrin et al., Phys. Rev. B 103, 104516 (2021). In the two-dimensional approximation, for circular obstacles (disks) moving in quiescent $^4$He, we calculated two critical velocities – one corresponding to the roton emission and the other to the nucleation of quantized
vortices – as functions of pressure and the obstacle's size. We also comment briefly on three-dimensional simulations of the roton emission and
vortex nucleation by moving spherical obstacles.
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All authors Nicolás Pablo Müller, Ladislav Skrbek, Yuri A. Sergeev, Giorgio Krstulovic
Statistical Mechanics
Universal classification of continuous phase transitions with two order parameters
Yilun Xu and Feng-xiao Sun
The continuous phase transition, indicated by the macroscopic order parameter and the occurrence of the spontaneous
symmetry breaking, is well illustrated based on the Ginzburg-Landau's paradigm. In systems described by one order parameter, the phase diagram is only composed of the normal phase and the ordered phase. However, in systems with two or more order parameters, much richer phase diagrams and critical phenomena may emerge. According to coupling terms of the free energy, we classify the systems with two order parameters into several categories, featuring different patterns of phase diagrams and critical scalings respectively. Our work propose the new avenue to studying and evaluating the complex systems only based on the coupling terms in expressions of free energy.
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Quantum Gases
Time crystals in cavity-BEC systems
Jayson G. Cosme and Ludwig Mathey
The understanding of light-induced dynamical states continues to be a challenging and fruitful pursuit of science. This pursuit is supported by
quantum simulation of dynamical phenomena, e.g., in ultracold atom systems. Typically, ultracold atom dynamics are read out destructively, via time-of-flight imaging, limiting a detailed analysis. However, atom-cavity systems provide a real-time readout of the photonic state via
photon emission from the cavity, making the system ideally suited for the simulation of dynamical phenomena. Here, we review three distinct time crystalline states, predicted and realized in a cavity-BEC system. We give an example for each of them, based on minimal few-mode models. We characterize the time crystalline states via correlation functions of the cavity mode, and characteristic momentum modes of the condensate. This supports a clear distinction between these time
crystals. More generally, the sequence of studies reviewed here, serves as a blueprint for setting up minimal models and their characterization, for dynamical phenomena.
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Materials Science
Photoluminescent Tetragonal Tb-doped Pb2P2O7
Yong Liu, Wenhua Bi, Alla Arakcheeva et al. (+1 more)
In this study, we report the synthesis and characterization of a novel tetragonal polymorph of Tb-doped Pb2P2O7. Single-
crystal X-ray diffraction confirms the stabilization of the P41 and P43 enantiomorphs at room temperature due to the incorporation of Tb3+ ions. Optical investigations reveal green photoluminescence from the characteristic 5D4 -> 7Fj (J = 1-5) transitions of Tb3+, with each emission split due to the
crystal field effect, indicating the presence of Tb3+ in multiple coordination environments. The power dependence of the PL intensity follows a linear power-law behavior, suggesting a one-
photon excitation process. Temperature-dependent PL measurements show an initial increase in intensity up to 125C, attributed to energy transfer from structural defects, followed by thermal quenching above this temperature. Structural stability at elevated temperatures is confirmed via high-temperature X-ray diffraction (XRD), showing no phase transitions before melting at approximately 800C. These findings highlight the potential of tetragonal Tb-doped Pb2P2O7 as a new class of photoluminescent material.
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All authors Yong Liu, Wenhua Bi, Alla Arakcheeva, Arnaud Magrez
Statistical Mechanics · Cross-listed from quant-ph
Quantum Quenches that Resemble Operator Growth
Xiangyu Cao
We study growth quenches, which are local quenches that may gradually destabilize a false
vacuum in certain kinetic constrained
quantum lattice models, such as the East-West model. We point out a formal analogy with the dynamics of a local operator in the Heisenberg picture. Exploiting this analogy, we obtain several results on growth quenches by adapting operator-dynamics concepts and methods. First, applying the Krylov approach (recursion method), we
conjecture the linear growth of Lanzcos coefficients in generic quenches, $a_m \sim \nu m$ (diagonal), and $b_m \sim \alpha m$ (off-diagonal), extending an operator growth hypothesis. We show that the growth quench dynamics is localized in both Krylov and Fock spaces when $|\nu| > 2 \alpha$, and derive a bound for the growth quench analogue of Lyapunov exponent $\lambda_L \le \sqrt{4 \alpha^2 - \nu^2}$ when $|\nu| < 2 \alpha$. Second, we realize the Fock localization in large $N$ solvable growth quenches inspired by Sachdev-Ye-Kitaev (SYK) models. The bound on Lyapunov exponent is saturated in large-$q$ SYK grow quench. By contrast, the growth quench is almost always Fock localized in a nonrandom all-to-all growth quench amenable to semiclassics. Finally, in the 1D East-West model, we interpret Fock space cage states as the existence of a conserved charge. We show that the latter has ballistic transport due to current conservation. Moreover, adding hopping with a fine-tuned amplitude induces a partial localization due to a flat band. Our work suggest growth quenches as a promising approach to realize non-
equilibrium coherent phenomena in many-body systems.
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Quantum Gases · Cross-listed from quant-ph
Coherent dynamics in chaotic spin chains via interference-protected subspaces
Aron Kerschbaumer, Jean-Yves Desaules and Maksym Serbyn
Generic
quantum many-body systems are expected to thermalize, scrambling initial coherence while local observables relax to
equilibrium values. Weak ergodicity breaking, often associated with
quantum many-body scarring of homogeneous states, provides rare exceptions with long-lived coherence. We introduce a family of local
spin-1/2 chains with a structured subspace that hosts a much broader range of nonthermal phenomena, such as scars, chirally propagating quasiparticles or approximate topological edge modes. These nonthermal phenomena happening at high energy densities can be understood via structured subspaces that are protected by destructive interference. We develop a quantitative leakage theory predicting which states retain coherence and suggest ways to improve the stability by inducing fast oscillations in the complement subspace. Our framework connects asymptotic scars,
quantum cages, and parent-
Hamiltonian constructions, and shows that weak ergodicity breaking in chaotic systems extends well beyond revivals of homogeneous initial states.
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Materials Science
Phase-dependent electronic structure of two-dimensional Ag layers at the graphene/SiC interface
Sawani Datta, Boyang Zheng, Arpit Jain et al. (+4 more)
Intercalation at the
graphene/SiC interface provides a controlled route to stabilize atomically thin layers with properties distinct from their bulk counterparts. In this platform, the structure and stability of the intercalated phase depend sensitively on the defect landscape of the starting substrate. For intercalated two-dimensional silver at the
graphene/SiC interface, two phases have been observed: a phase epitaxial to the SiC
lattice, Ag$_{(1)}$, readily obtained following the conventional intercalation method under ultra-high-
vacuum conditions and extensively characterized, and a more densely packed phase, called Ag$_{(2)}$, which has remained largely unexplored. Here we report an in situ ultra-high-
vacuum preparation method of the second phase intercalated at the
graphene/SiC interface; this phase previously was prepared via high-pressure confinement heteroepitaxy. Low-energy electron diffraction shows that Ag$_{(2)}$ is rotated by 30 degree relative to the SiC
lattice and forms supercells, in contrast to the $(1\times 1)$ epitaxial relation of Ag$_{(1)}$ with SiC. High-resolution angle-resolved photoemission spectroscopy reveals a more rich Ag$_{(2)}$ band dispersion compared to the Ag$_{(1)}$. In density functional theory calculations, by defining the unfolding
entropy which, in a quantified way, finds that the band structure of Ag$_{(2)}$ is more suitable to be unfolded to the SiC primitive
cell, and the resulting unfolded band dispersion is in great agreement with the experimental data. We further show that the different intercalated Ag phases tune the electronic properties of the overlying quasi-free-standing
graphene layer differently: compared with Ag$_{(1)}$, Ag$_{(2)}$ yields an $\sim$1.75 times higher charge carrier density and modifies the charge-plasmon interaction of the
graphene layer, indicating a change in effective screening at the interface.
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All authors Sawani Datta, Boyang Zheng, Arpit Jain, Kathrin Küster, Joshua A. Robinson, Vincent H. Crespi, Ulrich Starke
Quantum Gases · Cross-listed from hep-th
On the Ising/tricritical-Ising interface: From ${W}_3$ symmetry to Rydberg atoms
António Antunes and Junchen Rong
We consider interfaces between critical
spin-chains in different universality classes, described in the continuum limit by defect/interface conformal field theory (DCFT/ICFT). We focus on a conformal interface between the Tricritical Ising (TIM) and the Ising CFT exploring the possibility of its experimental realizations in the context of Rydberg atom arrays. Our analysis emphasizes non-invertible
symmetries and consistency under modular transformations, and uses defect couplings and the defect spectrum – including in the case of mixed boundary conditions – to make sharp experimental predictions. The structure of the observables hinges on a newly discovered pattern of emergent ${W}_3$
chiral symmetry for the Tricritical-Ising/Ising interface.
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Superconductivity
Quantum critical collapse of a pinned vortex glass in high-field superconducting resonators
David Perconte, Thibault Charpentier, Nikolaos Koutsopoulos et al. (+8 more)
The interplay between disorder and
vortex–
vortex interactions in strongly disordered
superconductors in a
magnetic field can stabilize a
vortex-glass state, characterized by strong pinning and the absence of positional order. Yet its role in the destruction of superconductivity at the field-driven
superconductor–
insulator transition has remained unresolved. Here we use plasmonic microwave spectroscopy of superconducting resonators patterned from amorphous indium
oxide thin films to directly track the superfluid density up to the critical field $B_c$. We find an unexpected resilience of the superfluid density, which decreases only logarithmically over nearly three orders of magnitude in field, in stark contrast to the rapid power-law suppression expected for
vortex lattices. We attribute this anomalously slow decay to a collective
vortex-pinning mechanism counterintuitively enhanced by
vortex–
vortex interactions. The superfluid density then vanishes linearly at $B_c$, where independent magnetoresistance measurements identify a continuous
quantum critical point, unlike the abrupt transition observed at zero field. We further uncover an exceptionally large nonlinear electromagnetic response of the
vortex glass, manifested as a pronounced positive-Kerr effect with potential for
quantum sensing. These results show how disorder controls the critical
magnetic field and identify the
vortex glass as the key intermediate state governing the
magnetic-field-induced
superconductor–
insulator transition.
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All authors David Perconte, Thibault Charpentier, Nikolaos Koutsopoulos, Kalpajit Roy, Nadjib Benchabane, Xiaoli Peng, Florent Blondelle, Frédéric Gay, Mikhail Feigel'man, Viktor Kabanov, Benjamin Sacépé
Mesoscale and Nanoscale Physics
Orbital Selective Dirac-like States in EuAgAs Revealed by Polarization Dependent ARPES and DFT
Mohit Mudgal, Suman Nandi, Mohamed El Gazzah et al. (+5 more)
Magnetic topological semimetals provide a promising platform for emergent
quantum phenomena driven by the interplay between magnetism and relativistic
fermions, including anomalous transport effects and tunable topological phases. Here, we investigate the electronic structure and orbital character of EuAgAs, a
magnetic topological Dirac semimetal candidate, using density functional theory (DFT) and polarization dependent angle resolved photoemission spectroscopy (ARPES).
Fermi surface mapping and constant energy contours measured at 9 eV reveal ring like features that systematically expand with increasing binding energy, consistent with nearly linear low energy Dirac like dispersion. ARPES measurements at different
photon energies hint at the presence of a van Hove singularity predicted by DFT calculations. Furthermore, this indicates that the photoemission
matrix elements are highly sensitive to the excitation energy, allowing different
photon energies to selectively probe distinct orbital characters. Polarization dependent ARPES measurements performed in s- and p-polarized geometries exhibit pronounced variations in spectral intensity, indicating
symmetry selective orbital contributions to electronic states. These
matrix element driven intensity modulations are well reproduced by DFT calculations. Furthermore, the observed Dirac like states remain nearly unchanged over the temperature range from 9 K to 30 K, suggesting that the
magnetic ordering has minimal influence on the electronic structure. Our combined experimental and theoretical results provide detailed insight into the orbital selective electronic structure of EuAgAs and its implications for
magnetic topological
quantum states.
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All authors Mohit Mudgal, Suman Nandi, Mohamed El Gazzah, Masashi Arita, Shin-ichiro Ideta, Nirmal J. Ghimire, Kenya Shimada, Anup Pradhan Sakhya