Strongly Correlated Electrons · Cross-listed from hep-th
On the SymTFTs of Finite Non-Abelian Symmetries
Oren Bergman, Jonathan J. Heckman, Max Hübner et al. (+3 more)
The $(D+1)$-dimensional
symmetry topological field theory (SymTFT$_{D+1}$) of a $D$-dimensional absolute
quantum field theory (QFT$_D$) provides a topological characterization of
symmetry data. In this framework, the SymTFT comes equipped with a physical boundary specifying a relative QFT, and a topological boundary which specifies the global form of
symmetries. In general, there need not be a unique bulk theory which encodes this information but it is often helpful to have a more manifest presentation of
symmetries in terms of bulk degrees of freedom. For the case of a finite non-Abelian
symmetry group $G$, the bulk SymTFT may be described by a Dijkgraaf-Witten TFT with gauge group $G$. This makes manifest the “electric” presentation of the
symmetry data but can obscure some of the
magnetic data as well as non-Abelian structure present in the absolute QFT$_D$ such as
symmetry operators which cannot fully detach from the topological boundary. We address these issues for 3D SymTFTs by constructing discrete BF-like theory Lagrangians for finite groups which admit a presentation as an extension by a finite Abelian group and a finite (possibly non-Abelian) group. This enables us to give a streamlined approach to reconstructing the fusion rules of the accompanying Drinfeld center, but also allows us to construct surface-attaching non-genuine line operators associated directly with non-Abelian group elements rather than just their conjugacy classes. We also sketch how our treatment generalizes to higher-dimensional SymTFTs.
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All authors Oren Bergman, Jonathan J. Heckman, Max Hübner, Daniele Migliorati, Xingyang Yu, Hao Y. Zhang
Statistical Mechanics · Cross-listed from hep-th
Outer automorphisms are sufficient conditions for RG fixed points
Thede de Boer and Andreas Trautner
We point out that the existence of an outer
automorphism (Out) is a sufficient condition for the existence of a fixed hyperplane (fixed point, separatrix) in the renormalization group (RG) flow of a
Quantum Field Theory (QFT). The corresponding RG fixed hyperplane is determined by a
symmetry argument and can be computed without resorting to perturbation theory. This provides the mathematical underpinning of 't Hooft's technical naturalness argument, and results in a systematic way to derive non-perturbative all-order constraints on the RG beta functions. If an Out exists, the
symmetry of the fully coupled system of beta functions is larger than the
symmetry of the action. We also stress the importance of including goofy transformations in these considerations.
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Disordered Systems and Neural Networks
Pruning-induced phases in fully-connected neural networks: the eumentia, the dementia, and the amentia
Haining Pan, Nakul Aggarwal and J. H. Pixley
Modern neural networks are heavily overparameterized, and
pruning, which removes redundant
neurons or connections, has emerged as a key approach to compressing them without sacrificing performance. However, while practical
pruning methods are well developed, whether
pruning induces sharp phase transitions in the neural networks and, if so, to what universality class they belong, remain open questions. To address this, we study fully-connected neural networks trained on MNIST, independently varying the dropout (i.e., removing
neurons) rate at both the training and evaluation stages to map the phase diagram. We identify three distinct phases: eumentia (the network learns), dementia (the network has forgotten), and amentia (the network cannot learn), sharply distinguished by the power-law scaling of the cross-
entropy loss with the training
dataset size. {In the eumentia phase, the algebraic decay of the loss, as documented in the machine learning literature as neural scaling laws, is from the perspective of statistical mechanics the hallmark of quasi-long-range order.} We demonstrate that the transition between the eumentia and dementia phases is accompanied by scale invariance, with a diverging length scale that exhibits hallmarks of a Berezinskii-Kosterlitz-Thouless-like transition; the phase structure is robust across different network widths and depths. Our results establish that dropout-induced
pruning provides a concrete setting in which neural network behavior can be understood through the lens of statistical mechanics.
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Strongly Correlated Electrons
Fracton Spin Liquid and Exotic Frustrated Phases in Ising-like Octochlore Magnets
Matthew Stern, Michael D. Burke, Michel J. P. Gingras et al. (+2 more)
For nearly three decades, research on frustrated magnetism in three dimensions (3D) has centered on the pyrochlore
lattice of corner-sharing tetrahedra and the classical
spin liquid (CSL) known as
spin ice. We propose that a
lattice of corner-sharing octahedra – the octochlore
lattice – may provide a next-generation platform for 3D frustrated magnetism, with realizations in anti-perovskite and alkali-rare-earth fluoride compounds. We study the phase diagram of Ising moments on the octochlore
lattice, finding a variety of frustrated phases including CSLs and phases with subextensive ground state degeneracy intermediate between
spin liquids and long-range order. Utilizing a cluster multipole framework, we present a unified treatment of this variety of frustrated behaviors. In addition to a
spin ice CSL, we identify a fracton CSL with excitations restricted to move along one-dimensional (1D) lines, a classical U(1) equivalent of the paradigmatic X-cube model harboring fracton topological order. These "lineon" quasiparticles carry
magnetic quadrupole moments, contrasting the famous
magnetic monopoles of
spin ice. These two CSLs lie at the boundaries of a parent "frustrated chains" phase with subextensive degeneracy. Each CSL corresponds to a condensate of different bound states of 1D ferro-spinons, giving rise to quasi-critical dimensional crossovers near the ends of the frustrated chains phase associated to avoided Kasteleyn-like transitions. We also find a
spin nematic phase whose ground states may be viewed as fracton
crystals, exhibiting both uniaxial and biaxial orders. The latter is caused by spontaneous dimensional reduction owing to accidental
symmetries of the subextensive ground state
manifold. This work paves the way for the realization of fracton CSLs and the exploration of other exotic states in underexplored octochlore
magnetic materials.
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All authors Matthew Stern, Michael D. Burke, Michel J. P. Gingras, Judit Romhányi, Kristian Tyn Kai Chung
Mesoscale and Nanoscale Physics · Cross-listed from quant-ph
Qubit measurement and backaction in a multimode nonreciprocal system
B. T. Miller, Lindsay Orr, A. Metelmann et al. (+1 more)
High fidelity
qubit readout is a cornerstone for
quantum information protocols. In traditional superconducting
qubit readout, a chain of microwave amplifiers and nonreciprocal components aid in detecting the
qubit's state with tolerable added noise and backaction. However, the loss, size, and
magnetic field of standard nonreciprocal components have sparked a decades-long search for more efficient and scalable alternatives. One prominent approach employs networks of parametrically coupled modes to achieve nonreciprocity. While this class of devices can be directly integrated with the
qubit's readout cavity, current understanding of the resulting single
quantum system is substantially lacking. Here we provide a first-principles theoretical tool to understand and design networks of linear modes integrated with embedded
qubits. We utilize this theory to inform and analyze the experimental implementation of a
qubit readout with an integrated three-mode nonreciprocal system. In doing so, we achieve excellent agreement between the experimental and theoretical
qubit measurement and dephasing rates. We then theoretically analyze the same system operated as an integrated nonreciprocal amplifier, predicting high efficiency for reasonable experimental parameters.
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All authors B. T. Miller, Lindsay Orr, A. Metelmann, F. Lecocq
Strongly Correlated Electrons
Interaction-Driven Ferrimagnetic Stripes in the Extended Hubbard Model
Chunhan Feng, Miguel A. Morales and Shiwei Zhang
Long-range interactions can qualitatively reorganize correlated-electron ground states. In the square-
lattice Hubbard model, on-site repulsion produces
antiferromagnetic spin and charge stripes upon doping. We show that including a nearest-neighbor repulsion $V$ can dramatically alter this behavior. Using auxiliary-field
quantum Monte Carlo and density
matrix renormalization group methods, we find that, above a critical ratio $V/U$ ($\sim 0.25$), the system develops a modulated ferrimagnetic order intertwined with checkerboard charge-density-wave. Inside the ferrimagnetic domains,
spin density alternates between positive (or negative) and nearly zero values. When the total
spin is fixed to zero, positive and negative domains alternate in space; when
spins are unconstrained, a ferrimagnetic state emerges with finite magnetization. Including a next-nearest-neighbor hopping $t'$ changes the modulation wavelength but leaves the order robust. Our results demonstrate that even short-range nonlocal interactions can stabilize qualitatively new
magnetic textures, with implications for cuprate materials and programmable
quantum simulators.
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Materials Science
Emergent Anomalous Hall Effect from Surface States in the Altermagnet MnTe Thin Films
Yufei Zhao, Saswata Mandal, Chao-Xing Liu et al. (+1 more)
Transport measurements on thin films of the prototypical altermagnet MnTe have reported conflicting phenomena of anomalous
Hall effects (AHE), including opposite signs and thickness-independent resistivity. Here we resolve these discrepancies by separating bulk and surface contributions to the AHE for different
crystal terminations. Using first-principles calculations and
symmetry-based effective models, we show that although the bulk hosts a characteristic $g$-wave
Fermi surface, surface states within the bulk gap acquire a ferromagnet-like
spin polarization and dominate the AHE at experimentally relevant
Fermi energies. While the surface magnetization follows the surface
spin sublattice, the resulting AHE is uniquely determined by the bulk Néel order for a given termination. Both bulk and surface contributions are closely linked to a small but finite out-of-plane orbital magnetization. Incorporating realistic interfacial chemistry further reveals that a Te capping layer can reverse the surface AHE sign relative to that on an InP substrate. Our results establish a microscopic framework for interpreting and engineering AHE responses in altermagnetic thin films through interface design.
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All authors Yufei Zhao, Saswata Mandal, Chao-Xing Liu, Binghai Yan
Strongly Correlated Electrons
Stable Topology in Exactly Flat Bands
Yan-Qi Li, Yi-Jie Wang, Pei-Han Lin et al. (+2 more)
Topological flat bands (FBs) offer an ideal platform for realizing exotic topological phases and exploring
quantum geometric effects, yet their realization with both exact flatness and stable
topology in local
lattice models has been hindered by fundamental no-go
theorems. The obstruction is also manifested as the absence of exact Gaussian TNS representations for topological
insulators and
superconductors. Here, we overcome this barrier by demonstrating the existence of critical topological FBs (CTFBs) in finite-range hopping models. They saturate the no-go
theorems via a unique structure of Bloch wavefunctions: While continuous over the whole Brillouin zone, the projector $P(k)$ onto FBs is non-analytic at isolated band touching points. Filling such CTFBs yields short-range entangled topological states with power-law correlations due to the non-analyticity. We then establish a general
symmetry-based principle to systematically construct CTFBs that carry desired topological invariants in given space groups. It utilizes the bipartite structure and requires no further fine-tuning, and the
topology is robust against arbitrary
symmetry-preserving gap-opening perturbations. Remarkably, independent tuning of the
quantum geometry is allowed. Examples exhibiting Chern numbers 1, 2, 3, 6, in 2D, and strong $\mathbb{Z}_2$ indices in 2D and 3D are demonstrated for concreteness. An automated
algorithm further identifies more than 50,000
symmetry-indicated CTFBs, including crystalline and higher-order topological ones. In the end, we show that the bipartite structure naturally endows the filled CTFB states with exact TNS representations with finite bond dimensions. By bridging the topological band theory to TNS methods, CTFB provides a novel tractable starting point for exploring strongly correlated topological matter, with potential relevance to realistic material realizations.
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All authors Yan-Qi Li, Yi-Jie Wang, Pei-Han Lin, Bin Wang, Zhi-Da Song
Mesoscale and Nanoscale Physics
Quantum Inductance as a Phase-Sensitive Probe of Fermion Parity Switching in Majorana Nanowires
Binayyak B. Roy, Jay D. Sau and Sumanta Tewari
We study the flux-dependent
quantum inductance of a one-dimensional (1D)
semiconductor-
superconductor (SM-SC) Majorana nanowire coupled to a
quantum dot in an interferometric setup. Although
quantum capacitance in this setup enables fast
fermion parity readout, as has been demonstrated experimentally, it cannot by itself reliably confirm a protected
fermion parity switch, a key signature of non-trivial
topology and the existence of Majorana zero modes (MZMs). In realistic devices, disorder can produce avoided crossings or narrow double crossings between the two parity sectors that can mimic the behavior of a protected single parity switching, leading to false positives for non-trivial topological behavior. We show that
quantum inductance provides a complementary probe that is directly sensitive to the phase structure of the low energy spectrum, allowing us to distinguish genuine
fermion-parity crossings from avoided crossings or narrow double crossings. Using a general Lehmann framework applied to both effective models and full microscopic simulations with disorder, we demonstrate that only a true
fermion-parity switch produces the characteristic inductive response of a protected crossing. In contrast, topologically trivial avoided crossings or narrow double crossings yield
quantum inductance signatures that are markedly different from those of topologically nontrivial
fermion parity crossings. Therefore, our results show that combined measurements of
quantum capacitance and
quantum inductance provide a robust and experimentally accessible means to identify true
fermion-parity switches, corresponding to a nontrivial Pfaffian invariant.
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Materials Science
A textured polar phase in strained SrTiO3
Huaiyu Hugo Wang, Ernesto Flores, Jade Stanton et al. (+11 more)
Quantum materials can harbour hidden phases whose microscopic structures differ from conventional ordered states while reproducing their macroscopic signatures, making them easy to miss. Strontium titanate is a longstanding puzzle of this kind: on cooling it shows every hallmark of an incipient ferroelectric, yet never orders, and is usually described as a
quantum paraelectric in which fluctuations suppress ferroelectricity. Here we combine uniaxial strain, single-cycle terahertz excitation and femtosecond x-ray scattering to measure the polar collective modes of strontium titanate as a function of momentum and strain. Under modest tensile strain, we observe a new vibrational mode that emerges not at the Brillouin zone centre, as a ferroelectric transition would require, but at finite wavevector, identifying the ordered state as a polar texture on nanometre length scales rather than a uniform ferroelectric. Unstrained
quantum paraelectric strontium titanate is then naturally understood as the disordered precursor of this textured phase, offering a resolution to a decades-old puzzle and illustrating how finite-momentum collective excitations can unmask hidden phases in
quantum materials.
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All authors Huaiyu Hugo Wang, Ernesto Flores, Jade Stanton, Gal Orenstein, Peter R. Miedaner, Laura Foglia, Maya Martinez, David A. Reis, Roman Mankowsky, Mathias Sander, Henrik Lemke, Serhane Zerdane, Keith A. Nelson, Mariano Trigo
Disordered Systems and Neural Networks · Cross-listed from quant-ph
Onset of Ergodicity Across Scales on a Digital Quantum Processor
Faisal Alam, Marcos Crichigno, Elizabeth Crosson et al. (+7 more)
Understanding how isolated
quantum many-body systems thermalize remains a central question in modern physics. We study the onset of ergodicity in a two-dimensional disordered Heisenberg Floquet model using digital
quantum simulation on IBM's Nighthawk superconducting processor, reaching system sizes of up to $10\times10$
qubits. We probe ergodicity across different length scales by coarse-graining the system into spatial patches of varying sizes and introducing a measure based on the collision
entropy of each patch, enabling a detailed study of when ergodic behavior emerges across scales. The high sampling rate of superconducting
quantum processing units, together with an optimal sample
estimator, allow us to access patches of sizes up to $3\times3$. We observe that as the Heisenberg coupling $J$ increases, the noiseless system undergoes a smooth crossover from subergodic to ergodic behavior, with smaller patches approaching their random-
matrix-theory values first, thereby revealing a hierarchy across scales. In the region of parameter space where classical tensor-network simulations are reliable, small patches or small values of $J$, we find excellent agreement with the error-mitigated
quantum simulation. Beyond this regime, volume-law
entanglement and contraction complexity growth causes the cost of classical methods to rise sharply. Our results open new directions for the use of
quantum computers in the study of
quantum thermalization.
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All authors Faisal Alam, Marcos Crichigno, Elizabeth Crosson, Steven T. Flammia, Filippo Maria Gambetta, Max Hunter Gordon, Michael Kreshchuk, Ashley Montanaro, Alberto Nocera, Raul A. Santos
Disordered Systems and Neural Networks · Cross-listed from quant-ph
Transition from Statistical to Hardware-Limited Scaling in Photonic Quantum State Reconstruction
Attila Baumann, Zsolt Kis, János Koltai et al. (+1 more)
The theoretical efficiency of classical shadow
tomography is predicated on a perfect Haar-random
unitary ensemble, yet this mathematical ideal remains physically unattainable in near-term hardware. Here, we report the experimental discovery of a fundamental accuracy bound on integrated photonic processors: a “Hardware Horizon” where the reconstruction error undergoes a sharp phase transition. While the error initially obeys the predicted statistical scaling $\mathcal{O}(M^{-1/2})$, it abruptly saturates at a floor determined by the spectral distortions of the realized
unitary group. By deriving a phenomenological error model, we decouple the competing mechanisms of static coherent spectral distortion and dynamic decoherence, demonstrating that this intrinsic noise floor imposes a hard bound that statistical accumulation cannot overcome. These findings establish that the utility of shadow
tomography on NISQ (noisy intermediate-scale
quantum) hardware is defined by a specific scaling law involving hardware parameters, necessitating active compensation strategies to bridge the gap between theoretical purity and the noisy reality of integrated photonics.
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All authors Attila Baumann, Zsolt Kis, János Koltai, Gábor Vattay
Disordered Systems and Neural Networks
Aleksey Lunkin
We develop a microscopic theory of thermalisation for a thermometer coupled to a many-body bath beyond standard Markovian and
Fermi-golden-rule assumptions. By modeling interaction
matrix elements in the non-interacting basis as independent random variables, we derive a
diffusion-propagator expression for the reduced dynamics and show that relaxation is controlled by the distribution of interaction-induced level broadenings. The theory predicts a thermalisation timescale set by the inverse typical broadening and yields a non-Markovian generalization of global balance. Exact-diagonalization tests for heavy-tailed Lévy couplings, an all-to-all transverse-field Ising model, and the one-dimensional Imbrie model show good agreement with these predictions.
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Mesoscale and Nanoscale Physics
Persistent altermagnetism
Warlley H. Campos, F. C. Fobasso Mbognou, Anna Birk Hellenes et al. (+4 more)
Persistent
spin textures with collinear
spin polarization are promising platforms for spintronics applications. However, their typically relativistic
spin-orbit origin leads to weak
spin splittings and fragile
spin coherence. Here, we demonstrate a previously overlooked class of robust collinear
spin polarization protected by mirror
symmetry in combination with a strong exchange-driven altermagnetic order, which persists even in the presence of
spin-orbit coupling. By combining first-principles calculations with a systematic classification of
spin and
magnetic layer groups, we identify this phenomenon-termed persistent altermagnetic
spin polarization (PASP)-to occur in 158
spin layer groups and in representative materials including metallic V$_2$Te$_2$O, insulating La$_2$CuO$_4$, and semiconducting VSI$_2$. Furthermore, we theoretically demonstrate that PASP is ferroelectrically switchable in VSI$_2$. Finally, we show that this PASP switching can lead to large changes in
spin-filtering conductance in a model all-altermagnetic junction. Our results open the possibility of employing PASP in all-altermagnetic
magnetic memory and
spin-transistor devices and establish universal principles of altermagnetism in
spin-orbit-coupled monolayers.
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All authors Warlley H. Campos, F. C. Fobasso Mbognou, Anna Birk Hellenes, Joseph Poata, Taikang Chen, Jan Priessnitz, Libor Šmejkal
Materials Science
A blended approach for evolving phase fields using peridynamics: Cyclic loading in quasi-brittle fracture
Hayden Bromley and Robert Lipton
A field theory is presented for predicting damage and fracture in quasi brittle materials. It is an expression of Newton's second law for an elastic-plactic continuum. The theory satisfies energy balance, with positive energy dissipation rate in accordance with the laws of thermodynamics. The formulation delivers a mesh free method for predicting crack patterns in quasi-brittle media and simulations show quantitative and qualitative agreement with experiments, including hysteresis and damage associated with three-point bending tests on concrete and size effects for quasi-brittle materials. We conduct numerical experiments exhibiting the competition between plastic yield strength and Griffith strength on fracture nucleation. This work has appeared in the Journal of the Mechanics and Physics of Solids, 216 (2026).
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Strongly Correlated Electrons
Kinetic obstruction to pairing in the doped Kitaev-Heisenberg ladder
Bradraj Pandey, Bo Xiao, Satoshi Okamoto et al. (+4 more)
We investigate the hole-doped Kitaev-Heisenberg ($t$-$J$-$K$) model on a two-leg ladder geometry using the density-
matrix renormalization group (DMRG). We first consider the behavior of the
antiferromagnetic Kitaev (AFK)
spin-
liquid phase as a function of hopping strength $t$ and doping level. This reveals intriguing pairing tendencies only for $\frac{t}{K} \lesssim 0.65$, consistent with prior results on three-leg ladders, and firmly supports the emerging picture that the physics of doped Kitaev
spin liquids strongly depends on the kinetic energy of the doped holes. Analysis of one- and two-hole doping uncovers close links between the spatial profiles of the plaquette operator and the charge density. We construct a doping-dependent phase diagram for
antiferromagnetic Heisenberg interactions and intermediate hopping $t=1$. Upon doping, the rung-singlet region develops dominant superconducting correlations. Charge-density-wave correlations dominate at weak doping near the transition to the stripy phase.
Spin-density wave-like behavior is found in the AFK and
ferromagnetic Kitaev limits, and in the stripy phase.
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All authors Bradraj Pandey, Bo Xiao, Satoshi Okamoto, Gonzalo Alvarez, Gábor B. Halász, Elbio Dagotto, Pontus Laurell
Superconductivity
A superconducting half-dome in bilayer nickelates
Yidi Liu, Bai Yang Wang, Jiarui Li et al. (+12 more)
Understanding how superconductivity emerges and collapses in correlated electron systems remains a central challenge in condensed matter physics. As a recently discovered member of the high temperature
superconductor family,
bilayer nickelates provide a new opportunity for examining this problem. Their pronounced sensitivity to oxygen stoichiometry, while posing challenges for stabilizing superconductivity, simultaneously offers an effective control parameter for tuning electronic phases. Here we report a superconducting half-dome in compressively strained
bilayer nickelate thin films as a function of continuous tuning of oxygen stoichiometry. Starting from an optimally superconducting state, increasing oxygen stoichiometry gradually suppresses superconductivity toward a metallic phase, whereas decreasing oxygen stoichiometry drives a granular
superconductor-to-
insulator transition while leaving the superconducting onset intact. This half-dome structure can be understood to arise from the contrasting roles played by interstitial oxygen versus oxygen vacancies - namely the dominance of doping versus scattering. Notably, the half-dome emerges consistently across samples with different rare-earth combinations, with or without alkaline-earth doping, revealing a general feature of the
bilayer nickelate phase diagram.
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All authors Yidi Liu, Bai Yang Wang, Jiarui Li, Yaoju Tarn, Lopa Bhatt, Michael Colletta, Yi-Ming Wu, Cheng-Tai Kuo, Jun-Sik Lee, Berit H. Goodge, David A. Muller, Zhi-Xun Shen, Srinivas Raghu, Harold Y. Hwang, Yijun Yu
Quantum Gases · Cross-listed from hep-ph
Schwinger Model with a Dynamical Axion
Gabriel Rouxinol, Tom Magorsch, Jesse J. Osborne et al. (+2 more)
One of the major open puzzles in the Standard Model of particle physics is the strong CP problem: although
Quantum Chromodynamics allows a CP-violating topological $\theta$-term, experiments constrain its value to be extremely small. The Peccei–Quinn mechanism resolves this problem by promoting the $\theta$-angle to a dynamical field-introducing the
axion – whose dynamics relax the effective angle $\theta_\text{eff}$ to a CP-conserving minimum. Here, we investigate the resulting
axion physics in a
Hamiltonian lattice gauge theory (LGT) by coupling a quantized
axion field to the massive Schwinger model with a topological $\theta$-term. Using infinite
matrix product state techniques, we compute the ground-state properties of the resulting theory and demonstrate that the
axion dynamically relaxes $\theta_\text{eff}$ to the minimum of the
vacuum energy. Consequently, the ground-state energy becomes independent of $\theta$, demonstrating the
axion-mediated solution to the strong CP problem within a fully dynamical LGT. We further analyze CP restoration and extract the
axion mass from the topological susceptibility and excitation spectrum. Our results provide a nonperturbative demonstration of
axion dynamics in a
quantum LGT amenable to investigation on modern
quantum hardware.
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All authors Gabriel Rouxinol, Tom Magorsch, Jesse J. Osborne, Nora Brambilla, Jad C. Halimeh
Statistical Mechanics
Non-Markovian Entropy Dynamics in Living Systems from the Keldysh Formalism
Feiyi Liu, Min Guo, Hongwei Tan et al. (+1 more)
Living systems are open nonequilibrium systems that continuously exchange energy, matter, and information with their environments, leading to
stochastic dynamics with
memory and active fluctuations. In this study, we develop a non-Markovian theoretical framework for the
entropy dynamics of living systems based on the Keldysh functional formalism and
stochastic thermodynamics. The approach naturally incorporates colored environmental noise,
memory-dependent dissipation, and many-body interactions, yielding generalized Langevin dynamics and non-Markovian master equations. Within this framework we derive an exact frequency-domain expression for the
entropy production rate and show that violations of the fluctuation-dissipation relation provide a direct thermodynamic signature of active biological fluctuations. We further demonstrate that environmental
memory enhances low-frequency fluctuations and
entropy production, leading to critical slowing down near dynamical instability. These results provide a microscopic physical foundation for the
entropy "bathtub" picture of living systems and connect
entropy evolution with development, aging, and death in nonequilibrium dynamics.
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All authors Feiyi Liu, Min Guo, Hongwei Tan, Yang Wang
Materials Science
Proof-Carrying Materials: Falsifiable Safety Certificates for Machine-Learned Interatomic Potentials
Abhinaba Basu and Pavan Chakraborty
Machine-learned interatomic potentials (MLIPs) are deployed for high-throughput materials screening without formal reliability guarantees. We show that a single MLIP used as a stability filter misses 93% of density functional theory (DFT)-stable materials (recall 0.07) on a 25,000-material
benchmark. Proof-Carrying Materials (PCM) closes this gap through three stages:
adversarial falsification across compositional space, bootstrap envelope refinement with 95% confidence intervals, and Lean 4 formal certification.
Auditing CHGNet, TensorNet and MACE reveals architecture-specific blind spots with near-zero pairwise error correlations (r <= 0.13; n = 5,000), confirmed by independent
Quantum ESPRESSO validation (20/20 converged; median DFT/CHGNet force ratio 12x). A risk model trained on PCM-discovered features predicts failures on unseen materials (AUC-ROC = 0.938 +/- 0.004) and transfers across architectures (cross-MLIP AUC-ROC ~ 0.70; feature importance r = 0.877). In a thermoelectric screening case study, PCM-audited protocols discover 62 additional stable materials missed by single-MLIP screening - a 25% improvement in discovery yield.
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Strongly Correlated Electrons
Pressure-Induced Chemical Bonding Effects on Lattice and Magnetic Instabilities in Antiferromagnetic Insulating CaMn$_2$Sb$_2$
Matt Boswell, Antonio M. dos Santos, Mingyu Xu et al. (+3 more)
Exotic
quantum phenomena often emerge near an electronic delocalization transition (EDT) from an
antiferromagnetic insulating phase to a strongly correlated metallic state under pressure. We report the pressure-induced structural and
magnetic evolution of the
antiferromagnetic insulator CaMn$_2$Sb$_2$. Single-
crystal X-ray diffraction reveals a first-order phase transition near 5.4 GPa from a trigonal P-3m1 structure to a monoclinic P2$_1$/m phase, accompanied by a ~7% volume collapse. Residual electron density analysis at intermediate pressures reveals charge localization along Mn-Sb chains, signaling electronic instability preceding the structural transition. Bonding analysis indicates anisotropic Mn-Sb orbital reconfiguration under pressure, driving a distorted square-pyramidal geometry.
Neutron scattering confirms the transition and identifies a pressure-induced incommensurate
magnetic order, distinct from the ambient
antiferromagnetic state. In the monoclinic phase, zigzag Mn chains exhibit
antiferromagnetic coupling along the ac-plane, enabled by enhanced orbital overlap. These results establish CaMn$_2$Sb$_2$ as a model system for studying the coupling of structural distortion, charge redistribution, and
magnetic order in layered Mn pnictides under pressure.
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All authors Matt Boswell, Antonio M. dos Santos, Mingyu Xu, Madalynn Marshall, Su-Yang Xu, Weiwei Xie
Mesoscale and Nanoscale Physics
Coherent perfect absorption of anti-modes in an indirect coupled magnon-polariton system
Chenyang Lu, Jiguang Yao, Jiongjie Wang et al. (+2 more)
In this work, we report coherent perfect absorption (CPA) of anti-modes in an indirectly coupled
magnon–polariton system. By examining both single and indirectly coupled cases, we experimentally distinguish the modal decay rate $\gamma$ from the effective decay rate $\gamma_{\rm{eff}}$. At CPA, $\gamma_{\rm{eff}} = 0$, leading to a vanishing output and a visually narrow spectrum in the dB-scale, while the intrinsic linewidth set by $2\gamma$ remains unchanged, demonstrating that the effective decay rate dictates the spectral amplitude rather than the physical loss. Furthermore, in the indirectly coupled system, CPA persists over a broad, magnetically tunable detuning range, in contrast to the single-detuning CPA observed in the directly coupled case, thereby enabling magnetically reconfigurable and frequency-selective microwave absorbers.
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All authors Chenyang Lu, Jiguang Yao, Jiongjie Wang, Jiang Xiao, Can-Ming Hu
Materials Science
Observation of Iso-Symmetric Structural and Lifshitz Transitions in Quasi-one-dimensional CrNbSe$_5$
Mingyu Xu, Peng Cheng, Shuyuan Huyan et al. (+5 more)
Chalcogenides-rich transition metal compounds host a rich landscape of emergent
quantum phenomena that are intimately governed by their quasi-one-dimensional chemical-bonding frameworks and their response to external perturbations such as pressure. Here, we report a pressure-induced iso-symmetric structural transition in the quasi-one-dimensional compound CrNbSe$_5$, in which the electronic ground state is controlled not by
symmetry breaking but by a continuous reorganization of local bonding interactions. Applied pressure reversibly tunes CrNbSe$_5$ between semiconducting and semimetallic states, enabling access to low- and high-carrier electronic regimes through direct modulation of metal-chalcogen bonding. High-pressure single-
crystal X-ray diffraction directly resolves the
evolution of Cr-Se and Nb-Se bond distances, coordination polyhedra, and connectivity, revealing a fully reversible semimetal-
semiconductor-semimetal transition driven by gradual yet cooperative bond rearrangements within a preserved crystallographic
symmetry. In contrast to chemical substitution, which irreversibly alters composition and introduces disorder, pressure acts as a clean, continuous control parameter that reshapes the bonding landscape without disrupting structural
symmetry. These results establish CrNbSe$_5$ as a model system for electronically driven phase switching via tunable chemical bonding, highlighting iso-symmetric bond reorganization as a powerful design principle for pressure-controlled electronic and spintronic functionalities.
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All authors Mingyu Xu, Peng Cheng, Shuyuan Huyan, Wenli Bi, Su-Yang Xu, Sergey L. Bud'ko, Paul C. Canfield, Weiwei Xie
Materials Science
Raman relaxation in Yb(III) molecular qubits: non-trivial correlations between spin-phonon coupling and molecular structure
Giacomo Sansone, Lorenzo A. Mariano, Stefano Carretta et al. (+2 more)
The coordination complexes of Yb(III) exhibit some of the longest
spin coherence times among 4f compounds, making them a promising platform for molecular
quantum technologies. While
spin-
phonon relaxation remains a limiting factor for coherence times even at low temperature, its control through chemical design has the potential to push these
spin qubits prototypes beyond current limits. With the aim of providing insights on how to chemically control
spin-
phonon relaxation, we here present a full ab initio study of
spin-
phonon dynamics for three Yb(III) molecules exhibiting minimal chemical differences, yet quantitatively different
spin relaxation times. Results show that low-temperature relaxation is governed by Raman processes triggered by a small group of largely delocalized low-energy
phonons. The analysis of these contributions highlights that the modulation of
spin-
phonon coupling by molecular structure modifications beyond the first coordination shell are highly non-trivial in nature and hard to rationalize in simple chemical terms. These findings call for a conceptual step change from the attempt to use simple magneto-structural correlations to interpret the effect of molecular structural modifications on
spin-
phonon relaxation, and present predictive first-principles frameworks as a potential driving force of future chemical design strategies
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All authors Giacomo Sansone, Lorenzo A. Mariano, Stefano Carretta, Paolo Santini, Alessandro Lunghi
Materials Science
Irradiation-induced amplification of electric fields at oxide interfaces as revealed by correlative DPC-STEM and DFT
Elizabeth A. Peterson, Dongye Liu, Sean H. Mills et al. (+5 more)
Heterointerfaces are ubiquitous in modern devices, found in technologies ranging from microelectronics to structural components for energy applications. Many of these emerging technologies are found in applications such as satellites, batteries, and next generation
nuclear reactors, that are subject to harsh environments. In some scenarios, multiple extreme conditions, such as irradiation and corrosion, act on the material simultaneously. Extending the lifetime of these technologies is dependent on a detailed understanding of how their component materials platforms and interfaces respond in extreme environments, where irradiation and corrosion may couple in unique ways, distinct from corrosion under ambient conditions.
Oxides, which form readily over metal underlayers, can act as protective coatings; enhancing the robustness of
oxide overlayers to protect underlying metal
alloys is a potential avenue towards corrosion mitigation. Here we study the impact of irradiation-induced non-
equilibrium defects on charge segregation and electric fields at and near multi-phase
oxide heterointerfaces. We perform a detailed study of irradiated Fe2O3-Cr2O3 thin film
heterostructures using first-principles DFT electronic structure modeling paired with 4D-STEM DPC and EELS techniques to measure nanoscale changes in electric fields. Our results show clear evidence that irradiation drives substantial modulation of interfacial electric fields that can be tailored by controlling the atomistic chemical structure of the
oxide interface. We show that irradiation can selectively induce built-in electric fields, thereby altering their direction; this suggests a pathway to engineering protective
oxide heterostructure overlayers that can electrically control the spatial distribution of defects, with significant implications for the design of corrosion-resistant materials for extreme environments.
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All authors Elizabeth A. Peterson, Dongye Liu, Sean H. Mills, Tiffany C. Kaspar, Hyosim Kim, Yongqiang Wang, Blas P. Uberuaga, Andrew M. Minor
Statistical Mechanics · Cross-listed from quant-ph
The Constrained Origin of Canonical and Microcanonical Ensembles in Quantum Theory
Loris Di Cairano
In
quantum theory,
equilibrium statistical mechanics is usually formulated through the canonical ensemble, whose privileged status is tied to the Euclidean continuation of time
evolution. The microcanonical ensemble, by contrast, is commonly introduced as a separate spectral construction. In this work we show that this asymmetry is representational rather than structural. We formulate the system in an extended
Hilbert space in which time is promoted to an auxiliary clock degree of freedom and physical states are selected by a reparametrization-invariant constraint operator $\hat C = \hat P_T + \hat H$. The corresponding projector $\delta(\hat C)$ provides a single unified object from which both canonical and microcanonical ensembles emerge as complementary projections in the clock sector. In the clock-time representation, a purely imaginary clock separation yields the Euclidean kernel and the canonical partition function. In the conjugate clock-energy representation, the same projector reduces to the spectral operator $\delta(\hat H-E)$ and hence to the microcanonical density of states. The main consequence is structural: canonical and microcanonical statistics need not be introduced as independent constructions, since both are already encoded in the same constrained
quantum dynamics.
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Soft Condensed Matter
Arrested coalescence drives helical coiling and networking of filamentous smectic condensates
Christopher A. Browne, Paul G. Severino, Yvonne Zagzag et al. (+5 more)
Liquid-
liquid crystal phase separation (LLCPS) occurs in many industrial and biological settings. Interestingly, when smectic phases demix from the homogeneous mixture, they can form filamentous condensates that spontaneously assemble into sparse networks with rich life-like dynamics. Here, we study the underlying process of filament networking. Microscopy reveals that new linkages between filaments are initiated by an adhesive interaction between straight filaments; parallel filaments snap into contact and then rapidly wind into helical coils, despite the absence of molecular chirality or transitions between mesophases. Using polarized optical microscopy, theoretical modeling, and simulation, we show that parallel filaments coalesce, but are arrested in double-barreled “ribbon” structures. This arrested coalescence is driven purely by interfacial energy minimization under the constraints of smectic layering. The arrested ribbons spontaneously coil into double helices to further reduce interfacial area, thus driving compaction into networks. We propose a microstructure consistent with this interpretation, which quantitatively predicts the extent of arrested coalescence. In total, these findings suggest a generic pathway for network formation in
liquid crystals that provides insight about the formation of condensate networks in other engineered or biological materials.
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All authors Christopher A. Browne, Paul G. Severino, Yvonne Zagzag, Jacob Z. Cloutier, Aaron C. Boyd, Yihao Chen, Arjun G. Yodh, Chinedum O. Osuji
Disordered Systems and Neural Networks · Cross-listed from physics.soc-ph
Why urban heterogeneity limits the 15-minute city
Marc Barthelemy
The `15-minute city' has emerged as a central paradigm in urban planning, promoting universal access to work and essential services within short travel times. Its feasibility-particularly for commuting to work-has however rarely been examined quantitatively. Here, we show that proximity to employment is fundamentally constrained by the internal structure of urban economies. Combining urban geometry with empirically observed firm-size distributions, we derive a lower bound on commuting times that holds independently of planning choices or transport technologies. This bound reveals a sharp transition: when employment is sufficiently concentrated, no spatial rearrangement of workplaces can ensure uniformly short commutes, even under optimal placement. Applied to Paris and its near suburbs, we find that achieving universal 15-minute commutes would require substantial economic restructuring or differentiated mobility strategies. The relevant question is therefore not whether an $x$-minute city is achievable, but what the minimal feasible $x$ is given a city's economic structure and spatial scale.
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Strongly Correlated Electrons
Directional Manipulation of a Staggered Charge Density Wave and Kondo Resonance in UTe2
Nileema Sharma, Fangjun Cheng, Hyeok Jun Yang et al. (+7 more)
UTe2 is a rare example of a correlated
quantum material in which unconventional density wave orders, Kondo physics,
spin-triplet pairing, and reentrant superconductivity coexist within the same electronic system. Its superconducting state develops out of a strongly correlated normal phase. The identification and control of competing or intertwined normal-state orders are thus central to elucidating the electronic landscape from which its superconductivity arises. Here, using scanning tunnelling microscopy (STM) in a vector
magnetic field, we uncover a previously unreported staggered charge-density-wave (CDW) in high-quality UTe2
crystals and demonstrate its strong directional response to an external
magnetic field: the staggered CDW is completely quenched by a modest 1.7 T field aligned with the quasi-one-dimensional uranium chain direction (a-axis), while remaining robust against fields along other crystallographic directions. This pronounced anisotropy is consistent with an orbital-driven mechanism that leads to a field-tuned
quantum phase transition. Strikingly and counterintuitively, the same field orientation and strength concomitantly alter the hybridization gap and suppress the 5f Kondo resonance. Modelling indicates that this correlated
evolution arises from a switch of the dominant hybridization channel from Te 5p- U 5f to U 6d- U 5f coupling, suggesting an intimate interplay between CDW and the Kondo effect. Our work establishes an effective tuning knob for the intertwined orders in UTe2 and provides evidence for orbital-selective Kondo hybridization, shedding light on its correlated normal state.
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All authors Nileema Sharma, Fangjun Cheng, Hyeok Jun Yang, Matthew Toole, James McKenzie, Mitchell M. Bordelon, Sean M. Thomas, Priscila F. S. Rosa, Yi-Ting Hsu, Xiaolong Liu
Superconductivity
Quantum interference in a twisted high-Tc SQUID senses emergent interfacial order
Amit Basu, Samrat Ash, Ritajit Kundu et al. (+12 more)
Engineering artificial systems by twisting and stacking van der Waals materials has proven to be an excellent platform for exploring emergent
quantum phenomena that can be significantly different from the constituents. Recent advances in the fabrication of high-quality twisted interfaces provide a unique opportunity to study the little-explored interfacial superconducting order in twisted cuprate
superconductors. In our work, we fabricate superconducting
quantum interference devices (SQUID) that utilize the twisted interface of $\mathrm{Bi_2Sr_2CaCu_2O_{8+\delta}}$, a high-Tc cuprate
superconductor. By measuring the
magnetic field modulation of switching current and differential resistance, we find a $\mathrm{\pi}$ phase difference between the two Josephson junction arms of the SQUID reflecting
chiral superconducting order – a crucial aspect inaccessible to single Josephson junction devices of the past. Our observations also indicate co-tunneling of the Cooper pairs and a time-reversal
symmetry-broken emergent superconducting order. Additionally, these SQUIDs are well suited for use as state-of-the-art flux sensors close to 77 K, achieving a flux noise sensitivity of $\sim$1.5 $\mathrm{\mu\Phi_0/\sqrt{Hz}}$. Stabilizing new superconducting orders using twisted interfaces and probing them using
quantum interference opens new avenues to understanding the microscopic origin of unconventional
superconductors. Our SQUID architecture is suitable for investigating the charge transport mechanisms and the
symmetry of superconducting order at the interfaces of other systems, reflecting the broad applicability beyond cuprate
superconductors.
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All authors Amit Basu, Samrat Ash, Ritajit Kundu, Neha Bhatia, Sakshi Nema, Tejaswini Gawade, Khushabu Agrawal, Abhishek Das, Joydip Sarkar, Amit Shah, Ruta Kulkarni, Digambar A. Jangade, Arijit Kundu, A. Thamizhavel, Mandar M. Deshmukh