Statistical Mechanics · Cross-listed from physics.chem-ph
Free energy differences and coexistence of clathrate structures II and H via lattice-switch Monte Carlo
Olivia S. Moro, Nigel B. Wilding and Vincent Ballenegger
We introduce a simulation technique to compute the free energy difference between two hydrate structures of different stoichiometry connected to a reservoir of gas molecules at a prescribed pressure. The method permits the determination of coexistence parameters for the system when the two hydrate structures have the same number of water molecules $N_w$. The approach is based on performing isobaric
Lattice Switch Monte Carlo simulations to measure free energy differences between the hydrate structures when they are either fully occupied by gas molecules, or fully empty. This measurement is combined with thermodynamic integration within an ensemble in which the number of guest molecules $N_g$ can fluctuate under the control of a chemical potential $\mu_g$. We analyze the properties of the resulting constant-$N_w,\mu_g,P,T$ ensemble and show how it can be used to calculate coexistence points via a thermodynamic cycle. Applying the method to argon and methane structures, we find coexistence pressures that are in good agreement overall with the available experimental data.
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Materials Science
X-ray Absorption and Resonant X-ray Emission at the Carbon Edge of Li$_2$CO$_3$
John Vinson, Terrence Jach, Rainer Unterumsberger et al. (+2 more)
While highly successful, density functional theory is known to have limitations owing to its neglect of many-body electron-electron interactions. This neglect leads to errors in the single-particle energies, leading to underestimated band gaps and band widths as well as errors in band
alignment at interfaces. Many-body perturbation theory, in the form of the $GW$ self-energy correction, has been widely used to improve upon these short-comings. Though less well studied, the same $GW$ method is also able to predict the finite quasiparticle lifetime that is seen to cause anomalous broadening in the lowest-lying lines of valence emission spectra. Using near-edge x-ray absorption and emission, we probe the electronic structure of Li$_2$CO$_3$. Our measurements are compared to first-principles calculations, including $GW$ self-energy corrections to the single-particle energies and excitonic effects from the Bethe-Salpeter equation.
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All authors John Vinson, Terrence Jach, Rainer Unterumsberger, Michael A. Woodcox, Burkhard Beckhoff
Statistical Mechanics
Global Oscillations in Depinning Models with Aging
F. V. Pereyra Aponte and E. A. Jagla
We propose a model that extends the standard depinning paradigm by incorporating an aging mechanism into the local pinning force. This favors oscillations between a stuck state of large pinning, and a slipping state of smaller pinning. We show that for mean field interactions between sites this mechanism can lead to the appearance of “king avalanches" and global instabilities, producing a global oscillatory stick-slip stress regime. We construct the phase diagram for this mean field case and identify regions of smooth dynamics, pure stick-slip, and bistability. Crucially, when considering two-dimensional systems with short-range interactions we find that states of global stress oscillation persist, but in contrast to the mean field case, no system-size avalanches appear. Instead, we observe alternating temporal intervals of larger and lower avalanche activity that correlate with the stress oscillations.
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Quantum Gases
Bosonic Working Media in a Frustrated Rhombi Chain: Otto and Stirling Cycles from Flat Bands, Caging, and Flux Control
Francisco J. Peña, Rafael García-Zamora, Gabriele De Chiara et al. (+5 more)
We demonstrate that flat-band engineering provides a direct route to control and optimize the thermodynamic performance of
quantum heat engines. We consider noninteracting
bosons on a rhombic chain
lattice described by a Bose-Hubbard model in the noninteracting limit, where a
magnetic flux serves as a tunable parameter that continuously reshapes the single-particle spectrum. By driving the system toward the fully frustrated Aharonov-Bohm caging regime, the band structure transitions from dispersive to completely flat, strongly modifying the thermal occupation of the modes. We show that this flux-induced spectral restructuring has clear and measurable thermodynamic consequences. In particular, the Otto cycle exhibits a significant enhancement of both work output and efficiency when operating near the caging regime. We identify the underlying mechanism as a pronounced suppression of heat released to the cold reservoir, rather than an increase in absorbed heat, revealing that flat-band formation is an effective strategy to increase work extraction. In contrast, the Stirling cycle is governed by
entropy changes during isothermal, flux-driven processes, leading to greater work extraction over a broader parameter range but at lower efficiency. These results establish
geometric frustration and Aharonov-Bohm caging as thermodynamic resources and show that spectral engineering via synthetic gauge fields offers a viable, experimentally accessible pathway to tailor the performance of bosonic
quantum thermal machines.
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All authors Francisco J. Peña, Rafael García-Zamora, Gabriele De Chiara, Jorge Flores, Santiago Henríquez, Nathan M. Myers, Felipe Barra, Patricio Vargas
Statistical Mechanics · Cross-listed from quant-ph
Simple slow operators and quantum thermalization
Tian-Hua Yang, Ethan Jeon, Sarang Gopalakrishnan et al. (+1 more)
We establish a rigorous operator-space condition for the thermalization of typical initial states. We introduce a concept of simple slow operators (SSOs), defined as operators that evolve slowly under Heisenberg-picture dynamics and have significant small-sized components. We show that the non-thermalization of typical initial states drawn from a weakly entangled state ensemble implies the existence of SSOs; equivalently, the absence of SSOs implies that typical initial states thermalize. We establish these results by introducing the concept of an ensemble variance norm of an operator, defined as the typical magnitude of the expectation value of that operator with respect to states in the ensemble. For low-
entanglement ensembles, the norm is related to operator sizes, allowing us to establish a direct link between operator dynamics and thermalization.
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All authors Tian-Hua Yang, Ethan Jeon, Sarang Gopalakrishnan, Dmitry A. Abanin
Statistical Mechanics
Genuine quantum scars in Floquet chaotic many-body systems
Harald Schmid, Andrea Pizzi and Johannes Knolle
Unstable periodic orbits act as organizing structures for classical chaotic systems and underpin
quantum scarring. Long known in single-particle systems, genuine
quantum scars based on unstable periodic orbits have been recently extended to isolated many-body systems for time-independent
Hamiltonians. Their fate under periodic driving, however, remains largely uncharted, challenged by the expectation that these systems should in general heat to infinite temperature. Here, we investigate how genuine scarring competes with the drive in a Floquet many-body system. Using chaotic
spin chains, we demonstrate that Floquet states remain scarred in the high-frequency limit. Beyond this static correspondence, we uncover additional, driving-induced Floquet scars with no static analog. We construct a rich dynamical stability diagram with intermediate-frequency regimes of enhanced and quenched scarring, which we understand with a classical analysis of the Lyapunov exponent. Our results position Floquet systems as a natural platform for tuning the scarring behavior of
quantum many-body systems.
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Strongly Correlated Electrons
Superconductivity near two-dimensional Van Hove singularities: a determinant quantum Monte Carlo study
Gustav Romare, Daniel Shaffer, Alex Levchenko et al. (+2 more)
The superconducting transition temperature $T_c$ of the two-dimensional attractive Hubbard model is computed in the vicinity of both ordinary (logarithmic) and higher-order (power-law) Van Hove singularities using determinant
quantum Monte Carlo simulations. For interaction strengths $|U| \lesssim W/3$, where $W$ is the electronic bandwidth, $T_c$ is enhanced in the neighborhood of the Van Hove point, albeit more weakly than expected from weak-coupling BCS theory. Enhancing the Van Hove singularity from logarithmic to power-law yields only a minor additional enhancement of $T_c$. For $|U| \gtrsim W/3$, the maximum $T_c$ shifts away from the Van Hove point and instead occurs at a density unrelated to any features in the non-interacting density of states, consistent with a strong-coupling interpretation. We find that the maximal $T_c$ in the model is achieved at intermediate $U$ and at a density away from the Van Hove point.
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All authors Gustav Romare, Daniel Shaffer, Alex Levchenko, Edwin Huang, Ilya Esterlis
Quantum Gases · Cross-listed from quant-ph
Programmable Fermionic Quantum Processors with Globally Controlled Lattices
Gabriele Calliari, Charles Fromonteil, Francesco Cesa et al. (+4 more)
We introduce a framework for realizing universal fermionic
quantum processing with globally controlled itinerant fermionic particles. Our approach is tailored to the example of neutral atoms in optical
lattices, but transposes to other setups with similar capabilities. We give constructive protocols to realize arbitrary fermionic processes, with time-dependent control over global parameters of the experimental setup, such as tunneling and interaction in a
Fermi-Hubbard type model. We first prove the universality of our framework and then discuss implementation variants, such as hybrid analog-digital simulation of extended
Fermi-Hubbard models, e.g., with long-range couplings.
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All authors Gabriele Calliari, Charles Fromonteil, Francesco Cesa, Torsten V. Zache, Philipp M. Preiss, Robert Ott, Hannes Pichler
Materials Science · Cross-listed from physics.ed-ph
Building an Affordable Self-Driving Lab: Practical Machine Learning Experiments for Physics Education Using Internet-of-Things
Yang Liu, Qianjie Lei, Xiaolong He et al. (+9 more)
Machine learning (ML) is transforming modern physics research, but practical, hands-on experience with ML techniques remains limited due to cost and complexity barriers. To address this gap, we introduce an affordable, autonomous, Internet-of-Things (IoT)-enabled experimental platform designed specifically for applied physics education. Utilizing an Arduino microcontroller, a customizable multi-wavelength light emitting diode (LED) array, and photosensors, our setup generates diverse, real-time optical
datasets ideal for training and evaluating foundational ML
algorithms, including traversal methods,
Bayesian inference, and deep learning. The platform facilitates a closed-loop, self-driving experimental workflow, encompassing automated data collection, preprocessing, model training, and validation. Through systematic performance comparisons, we demonstrate the superior ability of deep learning to capture complex nonlinear relationships compared to traversal and
Bayesian methods. At approximately $60, this open-source IoT platform provides an accessible, practical pathway for students to master advanced ML concepts, promoting deeper conceptual insights and essential technical skills required for the next generation of physicists and engineers.
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All authors Yang Liu, Qianjie Lei, Xiaolong He, Yizhe Xue, Kexin He, Haitao Yang, Yong Wang, Xian Zhang, Li Yang, Yichun Zhou, Ruiqi Hu, Yong Xie
Quantum Gases · Cross-listed from quant-ph
Floquet Many-Body Cages
Tom Ben-Ami, Roderich Moessner and Markus Heyl
Many-body cages have very recently emerged as a general route for nonergodic behaviour in
quantum matter. Here, we show that new types of many-body cages can be engineered in Floquet
circuits with the potential to realize novel nonequilibrium
quantum states. For that purpose, we first identify an explicit, general construction of Floquet
circuits capable of hosting many-body cages. We then present a generic strategy to engineer and structure Floquet many-body cages. We demonstrate the developed scheme for the
quantum hard disk model as a generic constrained model system, realizable for instance in Rydberg atom arrays. We construct Floquet
circuits yielding Floquet many-body cages with topological properties and $\pi$-quasienergy modes, implying `time crystalline' spatiotemporal order. Our results can be directly extended to general
quantum circuits, thus providing a new tool to engineer nonequilibrium behaviour in driven systems.
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Statistical Mechanics · Cross-listed from quant-ph
A complexity phase transition at the EPR Hamiltonian
Kunal Marwaha and James Sud
We study the computational complexity of 2-local
Hamiltonian problems generated by a positive-weight symmetric interaction term, encompassing many canonical problems in statistical mechanics and optimization. We show these problems belong to one of three complexity phases: QMA-complete, StoqMA-complete, and reducible to a new problem we call EPR*. The phases are physically interpretable, corresponding to the energy level ordering of the local term. The EPR* problem is a simple generalization of the EPR problem of King. Inspired by empirically efficient
algorithms for EPR, we
conjecture that EPR* is in BPP. If true, this would complete the complexity classification of these problems, and imply EPR* is the transition point between easy and hard local
Hamiltonians. Our proofs rely on perturbative gadgets. One simple gadget, when recursed, induces a renormalization-group-like flow on the space of local interaction terms. This gives the correct complexity picture, but does not run in
polynomial time. To overcome this, we design a gadget based on a large
spin chain, which we analyze via the Jordan-Wigner transformation.
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Materials Science
Evidence for Umklapp electron scattering emission from metal photocathodes
I-J. Shan, L.A. Angeloni and W. Andreas Schroeder
Comparison of the measured spectral emission properties of single-
crystal Cu(001) and W(111) photocathodes to established photoemission theories reveal evidence for an additional one
photon emission process predominantly affecting electron emission near and below the photoemission threshold. This additional photoemission process is postulated to be due to a momentum-resonant Franck-Condon mechanism mediated by inelastic Umklapp electron scattering. An initial first-principles simulation of this emission process (involving the electron thermal effective mass, the inelastic electron mean free path at the
vacuum level, and the number of
Fermi surfaces in the metal), when combined with a direct one-step band emission model, is consistent with the measured spectral dependencies of both the
quantum efficiency and mean transverse energy of electron photoemission from the two single-
crystal metal photocathodes.
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Strongly Correlated Electrons
Probing spinon interactions in the spin-1 bilinear-biquadratic chain
Yonatan Lin, Oleg A. Starykh and Anna Keselman
We study the dynamical
spin and nematic correlations in the bilinear-biquadratic
spin-1 chain in the critical phase hosting deconfined spinons. We demonstrate how spinon interactions can be directly probed in the presence of a
magnetic field or a single-ion anisotropy. Our analytical predictions are supported by numerical
matrix-product-state (MPS) simulations of the underlying microscopic model.
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Soft Condensed Matter
Variations on the Three-Sphere: Laves' Labyrinth Lopped
Lauren Niu and Randall D. Kamien
Inspired by the structure of $srs$ Laves networks in $\mathbb{R}^3$ that underpin the celebrated gyroid surface, we construct a Laves network of identical three-coordinated vertices on $S^3$ with double-twist. This network is a subset of the vertices and edges of the 600-
cell, and can be viewed as a bipartite graph of disjoint 24-
cell vertices inscribed in the 600-
cell. We describe mutually entangled realizations of this network on $S^3$, and describe their relation to the well-known $srs$ Laves network structure in $\mathbb{R}^3$.
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Strongly Correlated Electrons
Heavy fermion $\textit{d-f}$ hybrid and the SmB$_6$ low temperature phase
Anzhelika V. Buskina and Vladimir A. Zyuzin
In this Letter we theoretically study physical properties of a model of heavy
fermion $d-f$ hybrid. In the studied model two species of
fermions have dispersions with different masses, one being much heavier than the other. Hybridization between the
fermions at the crossing point of their dispersions doesn't open a true insulating gap leaving a heavy
fermion $d-f$ hybrid at the
Fermi level. As a result, our theoretical model qualitatively explains experiments on the low-temperature phase of the SmB$_6$. These are the linear in temperature specific heat, saturation of the resistance, and frequency dependence of the optical conductivity. Calculated optical conductivity shows a broadened peak at the twice the value of hybridization as well as a low-frequency tail.
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Mesoscale and Nanoscale Physics
Sensitive dependence of Poor Man's Majorana modes on the length of the superconductor
Zhi-Lei Zhang, Xin Yue, Guo-Jian Qiao et al. (+1 more)
In a hybrid system where two
quantum dots (QDs) are coupled to a conventional $s$-wave
superconductor, Poor Man's Majorana modes (PMMs) have been proposed. Existing theories often idealize the
superconductor (SC) as a bulk system or an infinitely long chain, or treat it as another
quantum dot with proximity-induced superconductivity, while experiments employ superconducting segments of finite length. Here, we model the SC as a finite-length 1D chain and treat the QDs and SC on equal footing. We obtain the conditions for the existence of PMMs, valid for arbitrary SC length and applicable to arbitrary tunneling strengths and
magnetic fields. We find that the number of PMMs is highly sensitive to the SC length: it oscillates between zero and two with a period set by the
Fermi wavelength ($\sim1\,\text{\AA}$), while four PMMs appear in the long-SC limit where the effective coupling between the two QDs becomes negligible. We further demonstrate that the PMMs that are separately localized at the two ends of the hybrid system do not exist in the finite-length case. Consequently, only nearly localized PMMs can be identified when the
magnetic field is strong enough. In this way, the generalized `sweet spot' of the practical system can be found.
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All authors Zhi-Lei Zhang, Xin Yue, Guo-Jian Qiao, C. P. Sun
Mesoscale and Nanoscale Physics
Spectroscopy of Heat Transport and Violation of the Wiedemann–Franz Law in a GaAs Hydrodynamic Mesoscopic Channel
Yu. A. Pusep, M. A. T. Patricio, M. M. Glazov et al. (+5 more)
The Wiedemann–Franz law, which determines the universality of the ratio of thermal conductivity to electrical conductivity, is studied in the hydrodynamic electron transport regime, where electron–electron scattering predominates over scattering by disorder. In this case, the different relaxation of electric and thermal currents can lead to a violation of the Wiedemann–Franz law, which is expected to be even more pronounced in mesoscopic electron systems. This paper reports the propagation of hot electrons in a GaAs hydrodynamic narrow channel, studied using micrometer-resolution photoluminescence thermometry. A temperature dependence of the Lorenz number was obtained, indicating a violation of the Wiedemann–Franz law. The important role of narrow constrictions in this violation was also demonstrated, and theoretical arguments are presented.
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All authors Yu. A. Pusep, M. A. T. Patricio, M. M. Glazov, V. A. Oliveira, M. D. Teodoro, A. D. Levin, A. K. Bakarov, G. M. Gusev
Mesoscale and Nanoscale Physics
Dynamical Poles in Non-Hermitian Impurity Scattering
Ao Yang, Kai Zhang and Chen Fang
In Hermitian
impurity scattering, each isolated late-time exponential is the fingerprint of a bound state. We show that this correspondence breaks down in non-Hermitian bands. For a single
impurity in a non-Hermitian
lattice, the late-time signal is controlled by isolated complex frequencies selected by the analytic continuation of the Green's function relevant to real-time dynamics, which we term dynamical poles (DPs). DPs need not coincide with static bound states: one may appear without any bound-state counterpart, while a static bound state may be dynamically invisible. The remainder of the signal is an incoherent background set by complex continuum edges. Our results establish that the real-time analytic structure of the Green's function, not the static
eigenvalue problem alone, organizes non-Hermitian
impurity scattering.
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Soft Condensed Matter
Inverse design of a magneto-elastica for shape-morphing
JiaHao Li, Yingchao Zhang, Weicheng Huang et al. (+4 more)
Slender
magnetic elements provide a versatile platform for programmable shape-morphing under remote
magnetic actuation. However, a general and physically interpretable framework for the inverse design of a 'magneto-elastica' under prescribed boundary conditions remains lacking. In this work, we develop an explicit analytical formulation for the inverse design of a magneto-elastica based on the integral form of the moment
equilibrium equations. Compared with purely local differential formulations, this integral approach makes the global constraints imposed by boundary conditions and moment balance explicit, and enables a systematic characterization of the feasible design space. We identify the key dimensionless parameters that govern the competition between
magnetic torques and elastic restoring moments and show that the applied boundary conditions are an essential ingredient. We obtain closed-form solutions for the beam tapering profiles required to generate desired actuated shapes in the cases of clamped–free and clamped–clamped configurations; in the latter case, this includes analytical expressions for the boundary reactions. The formulation recovers the classical inverse elastica in the absence of
magnetic fields and reveals a linear scaling between
curvature deviation and
magnetic mismatch. A tessellation strategy based on stiffness tailoring is further proposed for the design of discretized morphing surfaces. The theoretical predictions are validated against discrete elastic rod simulations and experiments across representative geometries. This work establishes a consistent analytical framework for the inverse design of a magneto-elastica and provides new insight into magnetically-induced shape programming in slender structures.
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All authors JiaHao Li, Yingchao Zhang, Weicheng Huang, Shenghao Ye, HengAn Wu, Dominic Vella, Mingchao Liu
Soft Condensed Matter
Building and maintaining a System of Intracellular Compartments
Amit Kumar and Madan Rao
Organelle patterning and its heritability remain central mysteries in
cell biology, highlighting the fundamental tension between genetic inheritance and self-assembly. Here, we explore the nonequilibrium assembly and emdedded size control of the Golgi cisternae and endosomes, amid a continuous flux of membrane traffic, within a
stochastic framework of mechanochemical fusion-fission cycles that violate detailed balance. Using a dynamical systems approach, we identify distinct, robust regimes, ranging from fixed points to limit cycles with definite phase relations between cisternae. We identify these dynamical regimes with diverse phenotypes, from stable cisternae to periodic,
cell-cycle-dependent dissolution/reassembly of cisternae to cisternal progression. We analyse its dynamic response to systematic perturbations or driving protocols and make definite predictions that may be tested experimentally. Our analysis reveals that the two competing models of Golgi organization - vesicular transport and cisternal progression - are, in fact, two phases of the same underlying nonequilibrium process. We see that cisternal size homeostasis is brought about by a size-dependent embedded control system driven by fusion-fission kernels. Finally, our framework offers a strategy for controlling cisternal number and chemical identity by modulating the interplay between glycosylation enzymes and membrane fission-fusion dynamics.
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Statistical Mechanics · Cross-listed from hep-lat
Hilbert Space Fragmentation from Generalized Symmetries
Thea Budde, Marina Kristć Marinković and Joao C. Pinto Barros
Hilbert space fragmentation refers to exponential growth in the number of dynamically disconnected Krylov sectors with system size. It is taken as evidence of ergodicity breaking, since conventional
symmetries generate at most a
polynomial number of sectors. However, we demonstrate that generalized
symmetries can fragment the
Hilbert space. Models with higher-form, subsystem, and gauge
symmetries can have exponentially many
symmetry sectors. We further prove that non-invertible
symmetries can induce additional fragmentation within individual
symmetry sectors. Fragmentation in several known models arises from generalized
symmetries, and the presence of exponentially many Krylov sectors therefore does not by itself imply ergodicity breaking. Finally, we show that disorder free localization arises naturally from Krylov-restricted thermalization when sectors lack translation invariance, requiring neither ergodicity breaking nor gauge
symmetry.
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Mesoscale and Nanoscale Physics
A. Shubnic, I. Chestnov, I. Lobanov et al. (+3 more)
We study the coupling between
spin excitations and acoustic waves in
bilayers of CrSBr, an ambiently stable 2D
magnetic material. We demonstrate that a strong dependence of inter-layer exchange coupling on strain makes possible the resonant generation of
magnons by an acoustic wave. It is shown that the parameters of the generation, in particular the resonant frequency, can be tuned by an external
magnetic field, which makes CrSBr a promising platform for spintronics applications.
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All authors A. Shubnic, I. Chestnov, I. Lobanov, V. Uzdin, I. Iorsh, I. A. Shelykh
Materials Science
Order-disorder transition and Na-ion redistribution in NASICON-type Na$_3$FeCr(PO$_4$)$_3$
Madhav Sharma, Archna Sagdeo and Rajendra S. Dhaka
We report the temperature-dependent synchrotron based X-ray diffraction analysis of NASICON type Na$_3$FeCr(PO$_4$)$_3$ sample, which undergoes a
symmetry-lowering structural transition from a monoclinic ($C2/c$) phase with long-range Na-vacancy order to a rhombohedral ($R\bar{3}c$) phase with statistical disordered Na ions. The [FeCr(PO$_4$)$_3$] polyanionic framework remains essentially unchanged, confirming that the transition is governed by redistribution of the Na sublattice rather than by reconstruction of the host framework. The structural
evolution is accompanied by a discontinuous increase in the $c$-axis and the unit-
cell volume, reflecting the progressive depopulation of the Na(1) sites and transfer of Na ions toward the Na(2) sublattice. The temperature dependence of superstructure intensity found to deviate from mean-field critical behavior, instead, the experimental
evolution is accurately captured by a sigmoidal phase-fraction model. The calorimetric measurements show that the enthalpy change for the first transition around 350~K is significantly larger than that of the anomaly around 445 K, indicating the dominant configurational rearrangement of Na ions occurs within the lower-temperature interval. Overall, the diffraction and calorimetric results demonstrate that Na ordering proceeds through an order-disorder transition involving intermediate Na configurations and a finite coexisting regime. The quantitative correlation between Na-vacancy ordering,
lattice strain, and
symmetry lowering reveals the central role of configurational interactions within the Na conduction channels in governing the phase stability of NASICON-type materials.
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Materials Science
All optical ultrafast pure spin current in the altermagnet Cr$_2$SO
Deepika Gill, Ruikai Wu, Peter Elliott et al. (+2 more)
All-optical generation of pure
spin current – the flow of
spin in the absence of a corresponding charge flow – relies on a
symmetry based compensation of valley charge. The 2d $d$-wave altermagnets, ideal spintronics materials due to a very low
spin-orbit coupling, possess a
magnetic point group and highly anisotropic valley
manifolds that would appear to preclude such current compensation, excluding them as materials for the ultrafast generation of pure
spin current. Here we show that infra-red valley excitation combined with a THz pulse envelope allows the generation of large and nearly 100% pure
spin currents in the altermagnet Cr$_2$SO. Our approach is based on a valley selection rule coupling linearly polarized light to
spin opposite valleys, along with the intrinsic momentum shift that a co-occurring THz pulse imbues a valley
spin excitation with. These results thus provide a practical and all-optical route to the generation of pure
spin current in $d$-wave 2d altermagnets, opening a route to lightwave control of
spin in an environment with very low intrinsic
spin mixing.
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All authors Deepika Gill, Ruikai Wu, Peter Elliott, Sangeeta Sharma, Sam Shallcross
Mesoscale and Nanoscale Physics
Heating Dynamics of Mesoscopic Electron Baths at High Magnetic Field
F. Zanichelli, A. Veillon, C. Piquard et al. (+8 more)
Quantum thermodynamics addresses the dynamics of heat flow in
quantum devices driven out of
equilibrium. Although mesoscopic
circuits at low temperatures provide a flexible platform to explore this dynamics, experimental studies are wanting because thermal timescales in nanodevices are often too fast. Here we engineer and investigate with noise thermometry a mesoscopic thermal
circuit where heat flows between electron,
phonon and
nuclear systems can occur on slower timescales. The central constituent of this device is a micrometer-scale metallic island electrically connected to large cold electron reservoirs through two to four ballistic
quantum Hall channels, a component frequently used for exploring stationary thermal currents. We uncover a two-step thermalization process specific to the mesoscopic scale, involving a fast initial temperature step followed by a much slower rise extending over minutes. This observation is quantitatively accounted for by the balance between heat flows through electronic
quantum channels, to cold
phonons, and to the
nuclear spins in the metallic island. The disclosed mesoscopic thermalization takes a step into the field of
quantum thermo-dynamical phenomena, highlighting their distinctive nature on a central constituent of
quantum circuits. The implications for the thermal engineering of nanodevices include the thermal characterization of exotic states at high
magnetic field.
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All authors F. Zanichelli, A. Veillon, C. Piquard, A. Aassime, Y. Sato, A. Cavanna, Y. Jin, J. Folk, U. Gennser, A. Anthore, F. Pierre
Materials Science
Piezomagnetic Switching of Nonvolatile Antiferromagnetic States
Xilai Bao, Oleksandr V. Pylypovskyi, Huali Yang et al. (+17 more)
Prospective spintronic
memory and logic devices will benefit from the negligible stray field and ultrafast
magnetic dynamics inherent to antiferromagnets [1]. However, realizing isothermal, nonvolatile, and deterministic switching of
antiferromagnetic states remains a key challenge [2, 3]. Here, we propose a piezomagnetic writing scheme in triangular Mn3Ir-based
memory cells, with readout achieved via the exchange bias effect. Our approach enables deterministic and nonvolatile switching of the
antiferromagnetic states, which exhibit exceptional robustness against external perturbations. The switching mechanism is ascribed to piezomagnetic effect of Mn3Ir combined with the interfacial Dzyaloshinskii-Moriya interaction at the antiferromagnet-ferromagnet interface. This scheme overcomes the speed limitations imposed by conventional isothermal methods based on isothermal crystallization mechanism [4]. Our findings highlight the potential of piezomagnetic effects in designing advanced spintronic devices, providing an efficient pathway for manipulating
antiferromagnetic states and developing energy-efficient
memory technology.
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All authors Xilai Bao, Oleksandr V. Pylypovskyi, Huali Yang, Yali Xie, Damien Faurie, Fatih Zighem, Sophie F. Weber, Jiabin Wang, Jiachen Liang, Hong Xu, Ruoan Zou, Huatao Jiang, Dong Han, Pavlo Makushko, Xiaotao Wang, Lin Guo, Proloy T. Das, Nicola A. Spaldin, Denys Makarov, Run-Wei Li
Strongly Correlated Electrons · Cross-listed from quant-ph
Alexander Altland and Julian Sonner
Recent years have witnessed tremendous progress in developing a fine-grained low-dimensional
holographic correspondence, specifically the construction of
quantum mechanical boundary theories as
holographic duals of two-dimensional
gravity. In these developments,
quantum chaos played a crucial role, both as source of universality and as a guiding principle for the matching of bulk and boundary signatures of
gravity. In this article we review the construction of the chaos-assisted low-dimensional
holographic correspondence for non-experts. We open with an introductory discussion of the two main protagonists of the theory, the SYK model and two-dimensional Jackiw-Teitelboim
gravity. Within this framework we will discuss two independent 'bridges' between bulk and boundary physics, one pertaining to early time chaotic instabilities, the other to late time
quantum chaos up to and including time scales of the order of the gravitational
quantum level spacing. We will demonstrate that the resolution of these fine-grained
quantum scales requires the extension of semiclassical
gravity by elements of string theory. We conclude with an outlook towards higher dimensional generalizations of the chaotic
holographic correspondence.
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Mesoscale and Nanoscale Physics · Cross-listed from physics.optics
Engineering strong coupling in ultra-compact photonic crystal/2D material platforms
Eleonora P. Kraus, Jamie M. Fitzgerald, Carlos Maciel-Escudero et al. (+1 more)
Sub-wavelength thick photonic
crystal (PhC) slabs coupled to 2D excitonic materials, such as transition metal dichalcogenides (TMDs), are a promising platform for highly tunable, room-temperature, on-chip optoelectronic devices. Unlike conventional Fabry-Perot microcavities, these compact open cavities exhibit non-trivial electric field profiles, leading to spatially distinct regions of weak and strong coupling with
excitons within the PhC unit
cell. Using coupled mode theory and rigorous solutions to Maxwell's equations, we investigate how the PhC geometry can be used to control these coexisting
exciton/polariton contributions and tailor the resulting optical spectra. For large filling factors, i.e., small air gaps, we show that PhC polaritons can be modeled as dark waveguide modes brightened via the periodicity of the PhC slab. Furthermore, by spatially patterning the TMD monolayer based on the local field intensity, we reveal the simultaneous presence of
excitons in both the weak and strong coupling regimes. Overall, this work provides fundamental insights into the strong light-matter coupling regime in structured photonic environments, offering a pathway to design and optimize metal-free, ultra-compact polaritonic devices.
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All authors Eleonora P. Kraus, Jamie M. Fitzgerald, Carlos Maciel-Escudero, Ermin Malic
Materials Science
Exact demagnetisation field for periodic one-dimensional array of rectangular prisms
Frederik Laust Durhuus, Andrea Roberto Insinga and Rasmus Bjørk
The
magnetic field from a uniformly magnetised, rectangular prism is known exactly, which is the basis for a large number of micromagnetic simulations. Here we derive an analytical solution for the field from a periodically repeating infinite array of prisms aligned end-to-end, which becomes exact on the center axis in the limit of infinitesimally thin prisms. Using the same method we derive the on-axis field for a one-dimensional array of point dipoles. We validate the obtained results numerically and furthermore compare with the common macrogeometry approach and more recent uniform magnetisation method, demonstrating an excellent convergence rate for the novel method.
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Statistical Mechanics · Cross-listed from quant-ph
Path Integral Approach to Quantum Fisher Information
Francis J. Headley, Mahdi RouhbakhshNabati, Henry Harper-Gardner et al. (+3 more)
We present a real-time path-integral formulation of the
quantum Fisher information for dynamical parameter estimation. For pure states undergoing
unitary evolution, we show that the
quantum Fisher information can be expressed as a connected symmetrized covariance of a time-integrated action deformation, equivalently as an integrated insertion of $\partial_\lambda S$ in the propagator. This reformulation avoids explicit state reconstruction by rewriting the
quantum Fisher information in terms of real-time correlators that are natural targets for many-body methods. We further embed the construction into the Schwinger-Keldysh closed-time-path formalism, identifying the
quantum Fisher information with the Keldysh component of an appropriate contour-ordered correlator generated by forward and backward propagating sources. Finally, using the Van Vleck-Gutzwiller approximation we re-derive the compact semiclassical
quantum Fisher information expression, clarifying how classical trajectory data control leading-order metrological sensitivity.
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All authors Francis J. Headley, Mahdi RouhbakhshNabati, Henry Harper-Gardner, Daniel Braun, Henning Schomerus, Emre Köse