Peer Revenue Fully funded

Papers

Fresh from arXiv, typeset properly. Highlighted words trade on the market.

Physics Condensed Matter

cond-mat Watch Condensed Matter

Saturday 26 September

Mesoscale and Nanoscale Physics

Helicity-Controlled Hall Transport in Hybrid Topological Magnetic Textures

Anton V. Hlushchenko, Julia Kharlan, Mykhailo I. Bratchenko et al. (+3 more)

Topological magnetic textures can serve as information carriers driven by spin currents. However, their motion is generally accompanied by a Hall effect that deflects them from the current direction, limiting transport efficiency and controllability. We develop a unified spin-space transformation framework enabling a systematic study of hybrid spin textures with different helicities, such as skyrmions, antiskyrmions, bimerons, and antibimerons. Combining analytical theory with micromagnetic simulations, we establish the relation between helicity and current-driven transport. An analytical solution of the generalized Thiele equation identifies helicity as a geometric control parameter and yields a simple expression for the Hall angle, enabling its continuous tuning, complete suppression, and deterministic steering along arbitrary in-plane directions. Micromagnetic simulations confirm that the generated spin textures remain stable under Landau–Lifshitz–Gilbert dynamics and validate the analytical predictions. These results establish helicity as a versatile control parameter for programmable transport of topological magnetic textures.
Read the full abstract

All authors Anton V. Hlushchenko, Julia Kharlan, Mykhailo I. Bratchenko, Aleksei V. Chechkin, Jarosław W. Kłos, Oleg A. Tretiakov

Quantum Gases

Pancake-shaped vortex droplets in dipolar molecular BECs

Zibin Zhao, Xinyi Tang, Tianmiao Zhang et al. (+6 more)

Anisotropic interactions profoundly affect topological excitations in quantum fluids. Motivated by recent advances in the studies of microwave-shielded polar molecules, we introduce self-trapped modes in the form of pancake-shaped quantum droplets (QDs) with embedded vorticity, which are maintained by strongly anisotropic dipole-dipole interactions. The stability region of singly charged ($S=1$) vortices nearly coincides with that of the ground-state QDs ($S=0$), demonstrating the robustness of the vortex states. The strong anisotropy of the system splits the core (pivot) of vortex QDs with $S=2$ into separated unitary ones. The angular momentum and stability of the state with $S=2$ are affected by the separation between the unitary cores. Higher-charge vortex QDs with $S>2$ are stable too, for sufficiently large particle numbers and inter-core separations. On the other hand, bound vortex-antivortex pairs with $S=\pm 1$ are unstable. Head-on collisions between the vortex QDs exhibit distinct regimes, including rebound, merger, and fragmentation. Tuning the cylindrically symmetric component of the dipolar interaction reveals a pronounced sign-dependent response: positive tuning preserves the self-bound vortex, whereas negative tuning drives expansion and fragmentation. The results demonstrate that the microwave-dressed molecular QDs offer a robust platform for the realization of self-trapped vortex states, demonstrating how the strong anisotropy reshapes their structure, stability, and dynamics.
Read the full abstract

All authors Zibin Zhao, Xinyi Tang, Tianmiao Zhang, Zhaopin Chen, Huanbo Luo, Guihua Chen, Bin Liu, Boris A. Malomed, Yongyao Li

Materials Science · Cross-listed from cs.LG

Phase Space Attention:A Hairer Lift Circumvents the Single-Layer Induction Obstruction

Kingsuk Maitra, Shagun Sood Morteza Hosseini, Suman Gunnala et al. (+1 more)

We circumvent the Sanford-Hsu-Telgarsky (SHT) single-layer induction obstruction within a linear, one-step, causal, bilinear, symplectically consistent design class on the post-RoPE substrate, by lifting attention onto a symplectic phase space, mirroring Hairer's lift of Stormer-Verlet. The lift exits the premise of the SHT counting argument rather than the bound itself. The reframing exhibits the obstruction as a filter-order gap: a one-layer bilinear score realises a $z$-transform of joint order $(0,0)$, whereas the induction discriminator requires key-side order $\geq 1$. Applying the symplectic upper shear $M_\gamma:(q,p)\mapsto(q+\gamma p,p)$ to the post-RoPE query and key streams closes it. We prove this lift is unique within the factorised subclass, exactly symplectic at operator level, and requires post-RoPE placement; and in an explicit $T_4$-only Gaussian reduction we derive a closed-form two-branch induction phase transition, held out at $r=0.9876$ with zero fitted parameters. That law is an analytically solvable limit, not a robust prediction: restoring the $T_3$ channel moves $\gamma_c$ at $d_k=64$ from 1.030 to 0.569 and removes the crossover. Deployability follows by exact derivation: the KV cache is unchanged, prefix reuse and speculative decoding are preserved, overhead is $6d$ FLOPs per token per layer, INT8 headroom grows by at most $\log_2(1+2\gamma)$ bits, fused kernels are unmodified, and no parameters are added. At 91.3M parameters a supercritical sweep locates an emergence band: induction forms 3/3 seeds at $\gamma=0.80$ in a mean of 717 steps, against 2/3 seeds and 2700 steps at $\gamma=0$. Adverse results are reported as directly: a key-only half-lift reaches 0.949 against 0.811 for the symmetric operator, so if induction accuracy is the objective, the half-lift is the better construction. Forty-one notebooks and result files ship as ancillary material.
Read the full abstract

All authors Kingsuk Maitra, Shagun Sood Morteza Hosseini, Suman Gunnala, Vikram Gupta

Statistical Mechanics

Continuously varying exponents in the distribution of waiting times in the symmetric exclusion process on a percolation cluster

Arpan Chatterjee, Kabir Ramola and Deepak Dhar

We study the waiting-time distribution of hard-core interacting particles in the symmetric exclusion process on one- and two-dimensional lattices with side branches attached to each lattice site in the steady state. We use numerical simulations together with an approximate analytical treatment of particles trapped in side branches in the steady state. Such a two-dimensional carpet serves as a simplified model for trapping of a supercritical percolation cluster. At high particle densities, the system exhibits strong dynamical heterogeneity, with the distribution of logarithms of waiting times developing well-separated peaks corresponding to particles trapped at different depths from the backbone. We show that the probability that a tagged particle occupies the same position at time $t_0+t$ as at time $t_0$ decays algebraically as $t^{-\omega}$, where the exponent $\omega$ varies continuously with particle density for densities above a threshold value $\rho^*<1$. We also investigate the correlations between successive waiting times along the trajectory of a tagged particle.
Read the full abstract

Strongly Correlated Electrons

Symmetry-permuting entanglers for non-invertible symmetry-protected topological phases

Minyoung You

1+1D symmetry-protected topological (SPT) phases with invertible symmetry can be characterized by the symmetric entanglers: globally symmetric finite-depth local unitary circuits that generate representative ground states from a product state. For non-invertible symmetries, however, distinct SPT phases, such as the three $\mathrm{Rep}(D_8)$ SPT phases, may not be connected by any symmetric entangler. We show that the three $\mathrm{Rep}(D_8)$ SPT phases can nevertheless be connected by symmetry-permuting finite-depth local unitary circuits, realizing dualities predicted by topological quantum field theory (TQFT). We construct an explicit matrix product unitary connecting two of the $\mathrm{Rep}(D_8)$ SPT phases, and show that its action on string order parameters reproduces the anyon permutation predicted by the TQFT duality.
Read the full abstract

Materials Science

Dopant-modulated lattice softening drives drastic thermal conductivity reduction in \beta-FeSi2 thermoelectrics

Cuiping Zhang, Qingyong Ren, Yangfan Cui et al. (+15 more)

Suppressing lattice thermal conductivity (K_lat) is pivotal for thermoelectric efficiency. While traditional strategies rely heavily on phonon scattering from mass- and size-mismatches, we demonstrate a robust K_lat suppression mechanism driven by dopant-induced lattice stiffness modulation. Through a comparative analysis of p-type (Mn) and n-type (Co, Ir) doping in the \beta-FeSi2 model system, we show that Co and Ir doping significantly reduce K_lat. Notably, Co doping achieves a ~71% reduction at 300 K even without significant mass and size contrast. By correlating transport data with neutron powder diffraction, heat capacity, and Raman spectroscopy, we reveal anomalous lattice expansion, a substantial reduction in Debye temperature, and marked vibrational redshift and broadening. These systematic changes provide strong evidence for atomic-scale lattice softening and a fundamental weakening of interatomic force constants, which synergistically lower phonon group velocities and amplify anharmonic scattering. Our findings establish lattice stiffness manipulation as a powerful strategy for thermal management, offering a distinct design pathway beyond traditional mass- and strain-fluctuation models.
Read the full abstract

All authors Cuiping Zhang, Qingyong Ren, Yangfan Cui, Chen Chen, Songbai Hu, Shengnan Dai, Chin-Wei Wang, Wanju Luo, Dexiang Gao, Bao Yuan, Junying Shen, Fan Chen, Wei Xu, Yuting Li, Mingfang Shu, Xiaoli Huang, Pengfei Qiu, Jie Ma

Quantum Gases

Quantum undular bores, rainbows, and event horizons in superfluid dam breaks

Liam M. Farrell, Wyatt Kirkby, Alex Harris et al. (+3 more)

The sudden removal of a potential barrier from a Bose-Einstein condensate (BEC) gives rise to a quantum version of a hydrodynamic dam break and leads to rich wave dynamics that have similarities to other localized defect problems such as domain wall dynamics in spin systems. Denoting $\Delta n$ as the initial difference in density between the upper $n_{1}$ and lower $n_{0}$ reservoirs on either side of the dam, we use the Gross-Pitaevskii equation to study the quasi-one dimensional case in both perturbative ($\Delta n \ll n_{0}$) and non-perturbative ($\Delta n \sim n_{1}$) regimes. In the perturbative regime a pair of outwardly propagating dispersive wavepackets forms which can be viewed as quantum versions of undular tidal bores that have analytic forms at long times in terms of the integrals of Airy functions with a wavelength that grows as $(\hbar^2 t)^{1/3}$. Airy functions are the universal wave functions that dress structurally stable fold caustics where pairs of rays coalesce, and, indeed, we show that the quantum dam break problem has the same ray structure as the naturally occurring caustic phenomenon of a double rainbow, including Alexander's dark band between the two bows where no light is scattered: we identify the intermediate density plateau in the dam break as an analogous `silent band' where only evanescent sound waves can exist. In the opposite regime of a non-perturbative dam break we show that a self-induced sonic horizon occurs when $\Delta n \geq (8/9)n_{1}$. A discussion of possible experimental schemes for amplification of quantum undulations is included as well as an alternative scheme for dispersive wave generation where a constant flow is imprinted on a BEC in box trap.
Read the full abstract

All authors Liam M. Farrell, Wyatt Kirkby, Alex Harris, David Tyler, Maxim Olshanii, Duncan H.J. O'Dell

Mesoscale and Nanoscale Physics

Enhancing magnonic frequency combs via geometric nonlinearity

Yushun Fang and Weichao Yu

Magnonic frequency combs (MFCs) generated via internal magnetic nonlinearities have exhibited rich physics beyond their optical counterparts. However, existing approaches rely on dynamic nonlinearity, which typically demands high power thresholds and stringent momentum conservation. Here we show that the geometric nonlinearity intrinsic to magnetic systems, originating from the unit-norm constraint of the magnetization vector, can serve as an independent nonlinear resource for MFC generation. Through transverse Floquet engineering, this geometric constraint converts a transverse drive into a longitudinal parametric modulation. In the low-frequency limit, the four-particle process reduces to an effective two-magnon modulation, enabling low-threshold comb generation in the linear regime, with the modulation amplitude scaling quadratically with the driving field and enhanced flatness arising from geometric harmonics. These results provide a deeper understanding of frequency combs and magnon nonlinear interactions, and offer a new theoretical foundation for enhancing MFC performance.
Read the full abstract

Mesoscale and Nanoscale Physics · Cross-listed from physics.optics

Geometry-Controlled Polarization Photocurrents in Scalable PtSe2 Infrared Pixels

Eunice Y. Paik, Owen A. Vail, Madaline R. Marland et al. (+11 more)

Polarization-sensitive photodetectors provide multi-dimensional optical information beyond the capabilities of traditional intensity-based detectors. The noble metal dichalcogenide PtSe2 presents unique opportunities for tunable polarization detection due to its strong spin-orbit coupling, material stability, customizable broadband polarization responses, and direct compatibility with a wide range of substrates for back-end-of-line silicon integration. In this work, we demonstrate room-temperature near-infrared to mid-wavelength infrared polarization photoresponses using scalable, as-grown, wide-area PtSe2 films, and we show that the measured polarization response is reshaped by device geometry. Finite-element current-flow simulations reproduce the observed spatial redistribution of the polarization-sensitive response and localize the transverse polarization response near the pixel center. This geometry-enabled separation allows wavelength-dependent laser spot scans to distinguish symmetry-allowed photocurrents from contact-proximate, dichroism-mediated photothermal contributions. At near-infrared wavelengths, we observe spatial response that is consistent with linear-dichroic photothermoelectric currents, whereas mid-wavelength infrared measurements reveal a helicity-dependent photothermal contribution under oblique illumination. These results identify pixel boundary engineering as both a design lever and a diagnostic tool for scalable PtSe2 polarization-sensitive infrared pixels.
Read the full abstract

All authors Eunice Y. Paik, Owen A. Vail, Madaline R. Marland, William A. Beck, Antonio Llopis-Jepsen, Wendy L. Sarney, Jeffery H. Leach, Stefan Heiserer, Nikolas Dominik, Cormac Ó Coileáin, Paul B. Seifert, Georg S. Duesberg, Blair C. Connelly, George J. de Coster

Mesoscale and Nanoscale Physics

In-Memory AM Demodulation Using an All-Silicon Independent-Dual-Gate Gain-Cell Memory with $<10^{-22}$ A Leakage Determined by Single-Electron Counting

Katsuhiko Nishiguchi, Toshiaki Hayashi, Kensaku Chida et al. (+3 more)

Ultra-low-leakage memories are attracting increasing attention for in-memory sensing and computing. However, achieving sufficiently long retention in silicon memories for analog signal processing remains challenging because of leakage through the access transistor. In this work, we demonstrate an all-silicon independent-dual-gate memory whose leakage current, inferred from single-electron counting statistics, is below $10^{-22}$ A, giving a measured retention time exceeding 1000 s. Owing to the extremely low leakage, the subthreshold nonlinearity of the access transistor can be exploited without disturbing the stored charge, enabling in-memory amplitude-modulation (AM) demodulation. The proposed memory provides a CMOS-compatible platform for ultra-low-power signal processing and in-memory sensing.
Read the full abstract

All authors Katsuhiko Nishiguchi, Toshiaki Hayashi, Kensaku Chida, Takase Shimizu, Gento Yamahata, Seiya Kasai

Materials Science

Temperature Dependent Evolution of the Electronic Structure in EuZn2As2 across the Neel Transition

Milo Sprague, Anup Pradhan Sakhya, Barun Ghosh et al. (+8 more)

Magnetoresistive materials have been tremendously important for the development of magnetic memory storage and spintronic devices. Recently, the antiferromagnetic EuX2Pn2 compounds, with X being a transition metal and Pn being a pnictogen, have seen intensive research interest due to their unusual anomalous Hall effect behavior and pronounced resistive anomaly near the Neel temperature (TN). These magnetotransport phenomena have been interpreted in the context of shortranged ferromagnetic Structuations, magnetic polaron formation, canted spin configurations, and temperature dependent metal insulator transitions in the electronic structure. Here, we report the observation of such a pronounced resistivity anomaly in EuZn2As2 near TN = 19 K. We demonstrate the suppression of this anomaly using applied magnetic fields, both in plane and out of plane. To further interpret the origin of the observed transport behavior, we studied the temperature dependent electronic structure using combined angle resolved photoemission spectroscopy (ARPES) and first principles density functional theory (DFT) calculations, which exhibits limited modifications to the bands across TN away from the Fermi energy. This lack of involvement of the electronic structure indicates a spin-scattering origin of the aforementioned transport properties, rather than a reconstruction of the Fermi surface.
Read the full abstract

All authors Milo Sprague, Anup Pradhan Sakhya, Barun Ghosh, Mazharul Islam Mondal, Arun K. Kumay, Himanshu Sheokand, Kapil Gope, Tetiana Romanova, Dariusz Kaczorowski, Arun Bansil, Madhab Neupane

Statistical Mechanics · Cross-listed from cs.AI

Escaping Alignment: A Physical Trap Model of Best-of-N Jailbreaking

Marco Biroli

Best-of-$N$ jailbreaking (BoN) bypasses safeguards of aligned models by drawing $N$ independent augmentations of an unsafe prompt and sampling $M$ completions of each. Previous works have shown that the attack success rate (ASR) seems to follow a power-law in $N$, which we challenge. The exponent drifts with $N$, with an exponential crossover which is a finite-size artifact of the adversarial dataset. Little work has been done to explore the entire two-budget ($N, M$) attack surface as well as its dependence on the generation temperature $T$. We introduce a simple barrier model where each prompt has a baseline safety level and each augmentation a random thermally activated barrier. Then four numbers, each backed by an interpretable safety mechanism, determine the entire ($N, M$) attack surface. They extrapolate predictions from $N \leq 100$ to $N = 10^4$, collapse five distinct models on the same scaling function and predict ASR at different temperatures from the one they were fitted at.
Read the full abstract

Materials Science · Cross-listed from cs.RO

Active 3D weaves for load-bearing and damage-resilient locomotion

Guowei Wayne Tu and Evgueni T. Filipov

The craft of weaving, where different materials are interlaced, has tremendous potential for creating active and functional systems for use in soft robots, prosthetics, wearables, exoskeletons, and more. These textile-like systems are flexible and safe for human-machine interaction; however, this inherent flexibility limits their ability to carry loads, which is essential for many robotic functions. In this work, we introduce a general framework for integrating active materials into three-dimensional (3D) woven shells to create robotic structures that combine high axial stiffness for load bearing, low bending stiffness for efficient actuation, and system-level resilience for damage tolerance. These woven robots can be modularly assembled from 'woven corners', a fundamental unit of 3D woven structures. We use eigenvalue calculations to identify load bearing and actuation mechanisms of the 3D woven structures, and use that information to make five different robots capable of locomotion. We demonstrate that these 3D woven robots can locomote carrying loads 70 times their self-weight, and can maintain repeatable performance even after being subjected to extreme compression. This work is a pathway toward the design, manufacturing, and simulation of future 3D woven robotic systems where load bearing, high stiffness, active functional deformation, locomotion, and system-level resilience are all needed.
Read the full abstract

Friday 25 September

Statistical Mechanics

Odd stochastic density functional theory

Yael Avni, Michel Fruchart, David Martin et al. (+2 more)

Stochastic density functional theory (SDFT) provides a powerful framework for studying the dynamics of many-body systems both in and out of equilibrium. In its standard form, it can be viewed as a density-based formulation of coupled Langevin equations with white noise. Here, we extend SDFT to a class of systems, ranging from magnetized electrolytes to chiral active matter, that possess a chiral overdamped limit in which a relaxation timescale and an oscillation period are simultaneously taken to zero. We derive this formulation, which we dub “odd SDFT", by taking the overdamped limit of a fluctuating hydrodynamic description of underdamped particles subject to a Lorentz force. We establish the validity and utility of the resulting framework by calculating the collective mobility tensor of interacting particles using both direct linear response and a Green-Kubo relation. We then apply the theory to the Hall conductivity of electrolytes in magnetic fields. Going beyond mean-field theory and using two distinct Green-Kubo relations, we derive the full conductivity tensor, extending the relaxation part of the Debye-Hückel-Onsager theory to the case of finite magnetic fields.
Read the full abstract

All authors Yael Avni, Michel Fruchart, David Martin, Tali Khain, Vincenzo Vitelli

Mesoscale and Nanoscale Physics

Magnetic Q-balls

A.J. Balseyro Sebastian, Keisuke Ohashi and Muneto Nitta

We study charged soliton branches in quasi-one-dimensional chiral magnetic systems with Dzyaloshinskii–Moriya (DM) interaction, easy-axis anisotropy, and Zeeman coupling. The same static magnetic functional is equipped with two different dynamical completions: an antiferromagnetic model with second-order time derivatives and a ferromagnetic model with Berry-phase dynamics. On the helical branch selected by the static DM interaction, the problem reduces to an analytically tractable one-dimensional system for the polar angle of the order parameter. We derive the existence conditions for polar Q-balls from the curvature of the reduced effective potential and the presence of a nonzero turning point. In the antiferromagnetic case, the allowed frequency window is symmetric and can be completely closed by the combined effect of the DM coupling and the Zeeman field. At zero Zeeman field, the same reduction also supports antiferromagnetic Q-kinks, for which we obtain explicit profiles, charges, energies, and reduced-sector fission criteria. In the ferromagnetic case, the Berry phase makes the rotation frequency act as a shifted Zeeman field. As a result, north- and south-pole charged droplets are selected by opposite signs of the shifted rotation. We also show that a formal pole-to-pole solution of the ferromagnetic mechanical problem does not generally correspond to a finite-energy magnetic soliton, because the Berry term does not renormalize the physical Hamiltonian. These results clarify how charged-soliton mechanisms depend on the underlying magnetic dynamics, even when the static chiral energy is the same.
Read the full abstract

Strongly Correlated Electrons

Chiral Weyl-Kondo semimetallic state through enhanced correlation in CeGaGe

Arushi, Kevin Allen, Yuan Fang et al. (+11 more)

Strongly correlated chiral materials have been proposed to host a chiral Weyl-Kondo semimetal (cWKSM) state, in which Kondo hybridization pins chirality-induced Kramers-Weyl point crossings, together with additional symmetry-enforced band crossings, near the Fermi level. Realizing this state requires a material that combines crystal chirality, non-symmorphic symmetry, and Kondo correlations, and currently there are no known materials that combine all these requirements. Here we report evidence for a cWKSM state in CeGaGe, a member of the RXY (R = rare earth; X = Al, Si; Y = Ga, Ge) family. Magnetization measurements confirm long-range antiferromagnetic order below T$_N$ = 4.7 K with a complex, canted magnetic structure. Unique to CeGaGe among the known RXY systems is a structural transition from an achiral tetragonal I4$_{1}$md structure (at high temperatures) to the chiral tetragonal P4$_{3}$ structure (at low temperatures). The structural transition in CeGaGe allows us to highlight the role of chirality in stabilizing the Kramers cWKSM state. Hall resistivity measurements with $H || c$ reveal an anomalous Hall conductivity (AHC) that is constant below the Kondo temperature $T_K \approx 7$ K and drops sharply above it. This crossover tracks the onset of Kondo coherence rather than the magnetic ordering, which occurs at T$_N$ = 4.7 K. Together with first-principles calculations for the $P4_3$ structure, this identifies the AHC as an intrinsic, Berry-curvature-driven contribution generated by Kondo hybridization, rather than a consequence of extrinsic scattering or dynamic scalar spin chirality. These results establish CeGaGe as a rare experimental platform in which crystal chirality, strong electronic correlations, and non-trivial band topology coexist, providing the first material realization of a Kondo-driven cWKSM state.
Read the full abstract

All authors Arushi, Kevin Allen, Yuan Fang, Kuan-Sen Lin, Mounica Mahankali, Hari Bhandari, Karthik Rao, Alberto Ruiz Biestro, Christopher Lane, Jian-Xin Zhu, Sanu Mishra, Geoffroy Hautier, Qimiao Si, Emilia Morosan

Mesoscale and Nanoscale Physics

Nanodiamond Sensing of Stray Fields during Domain Reversal

Kin On Ho, Hamza Abudayyeh, Andrew Perez et al. (+6 more)

Quantitative measurement of nanoscale stray magnetic fields during domain reversal is important for understanding and optimizing magnetic memory and logic devices. Yet, achieving high spatial resolution with minimally invasive probes remains challenging. Here we demonstrate nanodiamonds (NDs) hosting an ensemble nitrogen vacancy (NV) centers as local quantum sensors of domain-reversal stray fields in a CoFeB strip. During magnetic-field-driven reversal, the ND sensors resolve three distinct local responses depending on their positions relative to the strip: a positive frequency jump at the edge, an unexpected negative jump just outside the strip, and a negligible change near the center. These contrasting signals are quantitatively explained by magnetostatic boundary fields from micromagnetic simulations. We further implement a fully constrained fitting procedure for optically detected magnetic resonance spectra, enabling robust field extraction even when resonances are partially resolved. Together, these results establish NV-ND magnetometry as a simple, transferable, and quantitative approach for characterizing spatially heterogeneous magnetic fields in thin-films and spintronic devices.
Read the full abstract

All authors Kin On Ho, Hamza Abudayyeh, Andrew Perez, Hui-Ping Chang, Liang Juan Chang, Junwei Tong, Can Cui, Jean Anne C. Incorvia, Xiaoqin Li

Other Condensed Matter · Cross-listed from quant-ph

Quantum error mitigation from information dynamics

Philippe Suchsland, Thomas Schuster, Manuel S. Rudolph et al. (+3 more)

Overcoming experimental errors is a central challenge in quantum science. This challenge is particularly acute in large and complex quantum circuits, where quantum information spreads into exponentially many paths, foiling any direct attempt to understand errors' impact. In this work, we present a novel approach to understanding and mitigating experimental errors, based on a surprisingly compact representation of a quantum circuit's information dynamics, the reactivity function. The shape of a circuit's reactivity function governs its noise response, and its amenability to different error mitigation methods. From this viewpoint, we introduce two complementary such methods. The first, Pauli-path zero-noise extrapolation, fits a parameterized model to a circuit's reactivity function and uses it to accurately extrapolate to zero noise. The second, tunable error cancellation, filters a circuit's reactivity function to cancel noise on all information up to a threshold locality. Crucially, both methods feature a tuning parameter that allows one to systematically improve their accuracy until convergence. Across three circuit families from published experiments, our methods overcome conventional zero-noise extrapolation biases as large as 30%; at $\sim$$10^{-2}$ root-mean-square error, they reduce sampling cost relative to probabilistic error cancellation by up to a factor of $10^3$.
Read the full abstract

All authors Philippe Suchsland, Thomas Schuster, Manuel S. Rudolph, Nicholas Noll, Thomas E. O'Brien, Zlatko K. Minev

Soft Condensed Matter · Cross-listed from physics.flu-dyn

Reversibility and Multiplicity in Liquid-Vapor Phase Change

Luiz Eduardo Czelusniak, Alexander J. Wagner and Luben Cabezas Gómez

Using diffuse-interface theory, we uncover unexpected phase-change phenomena that are absent from widely used models of evaporation and condensation. In the inviscid limit, the same adjacent thermodynamic states admit stationary evaporation and condensation with equal and opposite mass fluxes, even when the vapor pressure lies below saturation. Viscosity breaks this reversibility but gives rise to multiple stationary condensation rates for the same vapor state. Lattice Boltzmann simulations dynamically recover these states, showing that these phenomena are dynamically realized by the diffuse-interface equations rather than arising solely as mathematical solutions of the reduced interfacial relations. Our results reveal previously unexplored behavior in a well-established theory of liquid–vapor interfaces.
Read the full abstract

Superconductivity

Quantum Geometric Origin of Yu-Shiba-Rusinov States

Rui-Xing Zhang

In this work, we revisit the classic Yu-Shiba-Rusinov (YSR) problem of magnetic impurities in $s$-wave superconductors and uncover a quantum geometric origin of the YSR bound-state structure. The key geometric quantity is the momentum-space average of Bloch band projector over low-energy electrons, whose matrix rank, positive eigenvalues, and corresponding eigenvectors directly control the number, energies, and symmetry representations of the YSR states, respectively. As a result, a superconductor with nontrivial normal-state quantum geometry can host more bound states than its trivial counterpart, even if they share the same electronic dispersion. We apply our theory to monolayer $1H$-NbSe$_2$ and find that the geometric texture of its single superconducting band enforces three symmetry-distinct YSR channels for a magnetic point impurity at Nb or Se sites. Our work opens a route to probing normal-state wavefunction geometry through local YSR spectroscopy.
Read the full abstract

Materials Science

Jahn-Teller Distortion-Driven Lattice Parameter Tunability in Coherent High-Entropy Oxide Thin Films

Dhiya Srikanth, Joseph Petruska, Matthew Furst et al. (+3 more)

Here, we isolate how Cu concentration and Jahn-Teller distortions control the out-of-plane lattice parameter of pseudomorphic MgCoNiCuZnO-derived high-entropy oxide films on MgO. We prepare nine compositions spanning 0-20% Cu, verify target composition and phase by X-ray fluorescence and diffraction, and grow films by pulsed laser deposition across multiple substrate temperatures. At 500 {\deg}C, the lattice parameter increases nearly linearly with Cu content; at 300{\deg}C, it decreases nonlinearly, producing a 2.6% difference between temperature regimes for equimolar MgCoNiCuZnO at our growth conditions. We attribute this change in lattice parameter to temperature-dependent coupling between Cu-driven Jahn-Teller distortions and Co valence change. While prior work identifies Co valence as the primary driver of the MgCoNiCuZnO lattice response with temperature; our results establish Cu Jahn-Teller distortion as an equally important structural control parameter.
Read the full abstract

All authors Dhiya Srikanth, Joseph Petruska, Matthew Furst, Kaylin Lamaute, Jon-Paul Maria, Saeed S. I. Almishal

Materials Science

The Young-E(3) Tensor Product Decomposition for Rotation and Permutation Equivariant Cluster Expansions

James M. Goff and Aidan P. Thompson

A generalization of fixed-lattice cluster expansions (CE) and atomic cluster expansions (ACE) is presented that expresses both rotation and permutation symmetries. By performing Schur–Weyl decomposition in Young subgroup-stabilized carriers, followed by joint coupling of rotation and permutation representations, arbitrary $S_N\times SO(3)$ tensor product carriers are generated. This allows us to resolve complete, orthonormal joint rotation and permutation-adapted bases for arbitrary tensor product ranks and arbitrary angular and radial tensor product content. We show that this very general Young–E(3) (YE3T) tensor product basis contains the ACE basis as a subset, corresponding to the special case where permutation symmetry character is restricted to the fully symmetric carrier. Rather than constructing an overcomplete rotation and permutation-invariant basis and reducing it a posteriori, Barthelemy et al. recently demonstrated scaling benefits by not constructing an overcomplete basis. YE3T directly produces a complete orthonormal basis without an overcomplete step and rigorously extends to permutation characters beyond permutation-symmetric features. The YE3T decomposition yields new joint irreducible rotation- and permutation-equivariant basis sets that surpass existing rotation-adapted expansions in both speed and accuracy, defining a new Pareto front for machine-learned interatomic potentials. We show that the tunability of the permutation symmetry character makes the basis useful for both atomistic and electronic-structure simulations.
Read the full abstract

Materials Science

Knowledge-Driven XRD Phase Identification via Multi-View Retrieval and Explanation

Doaa Mohamed and Markus Stricker

X-ray diffraction (XRD) is a experimental technique for determining the phase composition and structure of crystalline materials. However, interpreting XRD patterns is challenging, particularly in high-throughput materials discovery, where many novel materials may need to be characterized and no reference patterns are available. Consequently, machine learning is increasingly used to accelerate and automate the analysis while reducing errors associated with human interpretation. We propose a multi-decision framework for XRD phase analysis that integrates representation learning, similarity-based retrieval, and explainable decision support within a unified reference database. A convolutional autoencoder learns compact latent representations of XRD patterns that preserve structural similarity while remaining robust to variations arising from experimental noise and measurement conditions. By integrating multiple decision pathways within a shared latent space, the framework moves beyond single-label prediction toward ranked and interpretable phase analysis that mirrors expert practice. During inference, complementary decision mechanisms are applied, including latent-space classification and retrieval, explanation-guided similarity using Integrated Gradients, and composition-based similarity search. These mechanisms generate ranked candidate phase lists that are aggregated into a final prediction with an associated confidence score. Experiments on synthetic datasets demonstrate strong predictive performance, achieving 98.85\,% accuracy for crystal system classification and 95.82\,% accuracy for space group prediction on the test set, while maintaining robustness under realistic perturbations. The framework supports reliable, analyst-friendly identification of crystal phases and structures in high-throughput and exploratory materials discovery settings.
Read the full abstract

Disordered Systems and Neural Networks

Connecting finite-size scaling and renormalization-group flows in Anderson localization on random graphs

Ignacio García-Mata, Weitao Chen, John Martin et al. (+2 more)

We investigate the relation between two complementary descriptions of the Anderson transition on small-world random graphs: finite-size scaling of eigenfunction moments and renormalization-group (RG) flows of multifractal dimensions $D_q$. The RG flows recover the qualitative structure previously reported for the information dimension $D_1$, while their extension to other $D_q$ with smaller moment orders $q<1/2$ confirms the strongly multifractal nature of the localized phase characterized by a clear separation between multifractal and localized behaviors at strong disorder. On the other hand, we show that we can construct another beta function characterizing the flow of eigenfunction moments, whose collapse onto a single function across different disorder strengths provides a clear confirmation of single-parameter scaling property. These results indicate that the family of RG trajectories observed for the information dimension $D_1$ need not imply two-parameter scaling and Kosterlitz-Thouless like critical behavior. To characterize these properties, one should consider different observables, such as large $q>1/2$ and small $q<1/2$ eigenfunction moments, which are associated with distinct critical behaviors, in particular different critical exponents.
Read the full abstract

All authors Ignacio García-Mata, Weitao Chen, John Martin, Bertrand Georgeot, Gabriel Lemarié

Statistical Mechanics · Cross-listed from hep-th

Spread Complexity for Local Operator Quenches with Conserved Momentum

Ali Fatemiabhari

We study a family of locally excited states in two-dimensional conformal field theories in different setups, defined on the plane, on the cylinder, or at finite temperature. These states are constructed by assigning independent chiral and anti-chiral regulators to a local primary operator, leading to excitations carrying net momentum. We analytically calculate the first few Lanczos coefficients and the early time behaviour of the spread complexity associated with these states. Then, using numerical methods, we obtain the coefficients reaching larger Krylov indices and find the associated spread complexity for a longer range of time evolution. We also compare the rate of change of the resulting spread complexity with the proposed holographic dual quantity, related to the proper momentum of an infalling particle in the dual bulk, but we observe a mismatch.
Read the full abstract

Soft Condensed Matter

Mechanical Clustering of Cells via the ExtraCellular Matrix

Ran Glinowiecki, Shahar Goren, Oren Tchaicheeyan et al. (+4 more)

Tissues are composites of living cells and extracellular matrix (ECM), that jointly determine their unique mechanical behavior. Here, we experimentally demonstrate that contractile cells remodel the ECM by generating long-range bands of aligned and densified fibers that mechanically couple cells into multicellular clusters. Using a finite-element model, we quantify the collective mechanical interactions mediated by these ECM bands for various volume fractions of cells. The model incorporates contractile particles that mimic cell-active forces within a nonlinear biological gel, inducing stiffening internally rather than through external loading. We find that even a small volume fraction of contractile particles (approximately 10%), much below what is expected for percolation of sphere contacts, leads to internal stiffening, mediated by the high-concentrated stress bands between cells and is strongly dependent on the nonlinear mechanical response of the ECM. Percolation analysis of the band network reveals sharp transitions at a critical particle volume fraction, that aligns with the onset of internal stiffening. These results demonstrate that long-range interaction between contractile cells through the deformation of the medium has the potential to globally shape the structure and mechanics of the bulk gel, leading to a functional structure with modified properties. These modified macroscopic changes can define organizing principles in tissue patterning and morphogenesis.
Read the full abstract

All authors Ran Glinowiecki, Shahar Goren, Oren Tchaicheeyan, Bar Ergaz, Robin L. B. Selinger, Yair Shokef, Ayelet Lesman

Strongly Correlated Electrons

Read-Rezayi fractional Chern insulators in modulated Bernal graphene

Ruth Mora-Soto, André Grossi Fonseca, Raul Perea-Causin et al. (+3 more)

Fibonacci anyons provide a universal platform for topological quantum computation, and emerge as low-energy excitations in the $\mathbb{Z}_3$ Read-Rezayi phase in the fractional quantum Hall effect. However, realistic microscopic realizations of this phase in the absence of a magnetic field have remained elusive. We study a model of periodically modulated Bernal bilayer graphene with gate-screened Coulomb interactions. Using the recently developed target-phase optimization method in conjunction with band-projected exact diagonalization, we identify at filling $\nu=3/5$ a region of parameter space whose ground state is consistent with a Read-Rezayi fractional Chern insulator. The partially filled band from which it arises is a part of a two-band complex which mimics geometric aspects of the lowest and first Landau levels, with the ground state at $\nu=1/2$ consistent with the Moore-Read state. Our results suggest that modulated Bernal graphene can realize delicate non-Abelian fractional quantum Hall states at zero magnetic field, while demonstrating target-phase optimization as a practical route to discovering such phases in realistic, high-dimensional microscopic models.
Read the full abstract

All authors Ruth Mora-Soto, André Grossi Fonseca, Raul Perea-Causin, Hui Liu, Emil J. Bergholtz, Marin Soljačić

Strongly Correlated Electrons

Zoology of chiral superconductors in Chern bands

André Grossi Fonseca, Aidan Reddy, Ahmed Abouelkomsan et al. (+2 more)

Evidence for chiral superconductivity has recently been observed in several van der Waals systems including rhombohedral multilayer graphene and twisted bilayer MoTe$_2$. In the latter, superconductivity emerges at carrier densities near a fractional Chern insulator. This raises the question of what kinds of superconductors may emerge in a system of electrons in a topological band with strong repulsive interactions. Here, we adapt the target-phase optimization method to search for chiral superconductors in a minimal model of interacting electrons in a Chern band. We construct a differentiable loss function for superconductors from the sign oscillation of the pair-binding energy and combine gradient-based optimization with a rigorous screening procedure to identify and characterize superconductors. Applying this framework within exact diagonalization to spinless electrons in periodically modulated Landau levels with screened Coulomb interactions, we uncover a broad family of chiral superconducting phases. At filling $\nu=2/3$, we recover the previously identified $f-\mathrm{i} f$ hole superconductors and find additional $p\pm \mathrm{i} p$ and $f+\mathrm{i} f$ superconductors of both electrons and holes, occurring near and far from the limit of ideal quantum geometry. At $\nu=1/2$, we identify $p- \mathrm{i} p$ electron and $f-\mathrm{i} f$ hole superconductors and find, for the first time, a direct transition between chiral superconductors and composite Fermi liquids. Our results reveal that chiral superconductivity in Chern bands comprises a diverse landscape of competing pairing instabilities and establish target-phase optimization as a general strategy for searching for quantum phases in complex interacting systems.
Read the full abstract

All authors André Grossi Fonseca, Aidan Reddy, Ahmed Abouelkomsan, Liang Fu, Marin Soljačić

Strongly Correlated Electrons

Emergent low-energy many-body Hilbert spaces in Chern bands

Chen-Xin Jiang, Zi-Xiang Hu and Bo Yang

We show that in Landau levels and more generic Chern bands, the most relevant many-body subspace selected by realistic two-body interactions alone (e.g., in the limit of vanishing bandwidth and band gap) depends strongly on the particle density and can be constructed systematically. Using the well-defined hierarchical structure of conformal Hilbert spaces (CHS), each with a highest-density vacuum state, we compute, for both fermionic and bosonic systems, the many-body quantum metric that quantifies the interaction energy scales of these subspaces. For a large family of short-range, Coulomb-based interactions, particles preferentially occupy the many-body states in the smallest accommodating CHS. This allows us to describe the low-energy physics of the interacting system in terms of the appropriate anyonic degrees of freedom. Our results also explain why, in any Chern band (in lattice or continuum systems), band mixing tends to be suppressed even in the limit of strong interaction; this suppression is stronger when the band deviates less from the ideal trace condition and when the two-body interaction is shorter-ranged.
Read the full abstract

Strongly Correlated Electrons · Cross-listed from quant-ph

Probing the classical complexity of quantum dynamics experiments

Thomas Schuster and Andreas Elben

A confluence of recent works has shown that many quantum circuits and dynamics are efficiently simulable by classical algorithms that track local information, even when conventional complexity measures such as the entanglement and magic are high. Here, we introduce a novel measure of complexity, the reactivity, to capture this new method of classical attack. Unlike conventional complexity measures, the reactivity does not capture a property of a quantum state or operator in isolation, but rather a quantum experiment as a whole. We provide numerical and rigorous evidence that quantum experiments with low reactivity are simple by a host of measures: they are efficient to classically simulate, learn, and fast-forward. This motivates the search for quantum experiments with high reactivity, which may evade these simplistic features. To this end, we introduce easily implementable experimental protocols—dubbed Pauli path spectroscopy—that allow one to efficiently measure the reactivity of any quantum experiment of interest. Our protocols are applicable even when the experiment itself is beyond the reach of classical simulation.
Read the full abstract