Mesoscale and Nanoscale Physics
Unveiling Topological Fusion in Quantum Hall Systems from Microscopic Principles
Arkadiusz Bochniak, Shinsei Ryu, Jürgen Fuchs et al. (+1 more)
Establishing the fusion rules of anyonic quasiparticles in fractional
quantum Hall fluids is essential for understanding their underlying topological order. Building on the
conjecture that key topological properties are encoded in the ”DNA” of candidate many-body wave functions - that is, the pattern of dominant orbital occupations restricted to a finite number of lowest Landau levels - we propose a combinatorial framework that derives these fusion rules directly from microscopic data. By extending Schrieffer's counting argument and introducing classes of topological excitations, our framework provides a unified route to the fusion rules for both Abelian and non-Abelian excitations. This approach elucidates the emergence of topological features from first principles in both fermionic and bosonic systems. In particular, we unveil the previously unknown fusion rules of the Hafnian fluid.
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All authors Arkadiusz Bochniak, Shinsei Ryu, Jürgen Fuchs, Gerardo Ortiz
Superconductivity
Control of turn-to-turn contact resistivity in resistively insulated REBCO coils
Jun Lu, Kwangmin Kim, Iain Dixon et al. (+6 more)
Resistively insulated (RI) REBCO magnets feature short ramp times and low ramp losses while maintaining the advantages of no-insulation coils with high engineering current density and tolerance for defects in the REBCO conductor. Control of the turn-to-turn contact resistivity Rc is key to RI technology. Rc must be sufficiently high to prevent a large transient current, which could result in high mechanical stress during magnet quenches. Meanwhile it must be lower than the quench propagation limit to avoid conductor burn-out during a quench. Therefore, it is critical to control Rc within a suitable range of values which is usually coil specific. Previously, we discovered that Rc between two REBCO tapes with a stainless steel interlayer decreases dramatically with contact pressure cycling by up to three orders of magnitude. This drastic change made it impossible to design a suitable Rc value for a stainless steel co-wound RI magnet. In this work, we first present methods for mitigating Rc pressure cycling sensitivity. We found that by adding conductive fillers, such as conductive paste or epoxy, the Rc load cycling sensitivity is largely mitigated. For dry-wound coils, Rc load cycling sensitivity is mitigated by coating REBCO tape with a layer of 2- 3 um of PbSn solder. In addition, Rc can be controlled by oxidizing the stainless steel co-wind tape by heating stainless steel tapes at different temperatures in air. Using above methods, short sample tests showed that Rc was controlled to prescribed values of 1000 and 5000 uOhm-cm2 and was not sensitive to contact pressure cycling up to 30,000 cycles at 4.2 K. The new Rc control method was applied to a 6 double-pancake test coil which was tested at 4.2 K. The Rc in this test coil was comparable with the short sample results. This demonstrated the ability of this new method to control Rc in large coils.
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All authors Jun Lu, Kwangmin Kim, Iain Dixon, Justin Deterding, Emsley Marks, Brent Jarvis, Denis Markiewicz, Hongyu Bai, Mark Bird
Materials Science
Hole concentrations in doped gray {\alpha}-Sn on InSb and CdTe measured with infrared ellipsometry
Jaden R. Love, Carlos A. Armenta, Atlantis K. Moses et al. (+5 more)
Gray tin ({\alpha}-Sn) layers with 30 nm thickness were grown on InSb (001) substrates using molecular beam epitaxy. The surface preparation of the substrates was adjusted to achieve either n-type or p-type doping in the {\alpha}-Sn layer.
Fourier-transform infrared ellipsometry was used to find the temperature-dependent dielectric function of the {\alpha}-Sn layers from 0.03 to 0.8 eV and from 10 to 300 K. Because of the inverted band structure of {\alpha}-Sn, the spectra show a strong absorption peak at 0.45 eV due to transitions from the inverted {\Gamma_-^7} "electron" valence band to the {\Gamma_+^8} heavy hole valence band. Applying the Thomas-Reiche-Kuhn f-sum rule, the integrated oscillator strength of this peak was used to calculate the heavy hole concentration as a function of temperature. For a nearly intrinsic {\alpha}-Sn layer, the heavy hole concentration agrees well with predictions based on degenerate
Fermi-Dirac statistics. Deviations from the intrinsic {\alpha}-Sn carrier concentrations are attributed to substrate surface preparation leading to the
diffusion of donor or acceptor ions into the {\alpha}-Sn layer causing n-type or p-type doping.
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All authors Jaden R. Love, Carlos A. Armenta, Atlantis K. Moses, Haley B. Woolf, Jan Hrabovsky, Stefan Zollner, Aaron N. Engel, Christopher J. Palmstrøm
Soft Condensed Matter
Universal Loop Statistics from Active Extrusion with Kinetic Barriers
A. Chervinskaya, R. Metzler and K. E. Polovnikov
We develop a kinetic theory of cohesin-driven loop extrusion on a disordered chromatin track with transient barriers. In the stationary state, the mean loop size is shown to obey a universal law determined by the bare processivity and a renormalized obstacle density. Beyond the mean, one-sided extrusion always yields a single-exponential loop-length distribution, whereas two-sided extrusion produces a finite sum of exponential modes and, generically, a peaked distribution. Experimental CTCF-anchored loop statistics exhibit such a peak, thereby providing a direct discriminator of extrusion
symmetry. The theory therefore establishes a unified framework for disorder-limited loop extrusion and supports a scenario in which both cohesin arms actively operate in living
cells.
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Soft Condensed Matter
Formation of cylindrical shells via sphere packing from fluidized beds
Vinícius Pereira da Silva Oliveira, Danilo da Silva Borges, Erick de Moraes Franklin et al. (+1 more)
The results of a numerical investigation of fluidized beds of spherical particles in a narrow vertical cylindrical pipe, with particular
attention to the spontaneous settling along the wall, are reported. Starting from a steady fluidized state, the particles fluctuate because of fluid-particle, particle-particle, and particle-wall interactions. The particles are heavier than the fluid, with diameters d yielding ratios of pipe to particle diameters D/d=4.3 and 4.7. For given ranges of flow velocities and bed sizes, particles settle on the wall, with a decrease in the bed height and particle fluctuations. Either a glass- or
crystal-like shell forms along the pipe wall, in qualitative agreement with previous experiments. The polydispersity and the particle-particle friction are varied to test the stability of the particulate shell formation. The shell structure is analyzed by unwrapping it in a plane and locating all particles and their contact points, and we find that it exhibits a hexagonal
lattice with a defects density that increases with polydispersity. The shell formation is hindered by polydispersity, and there exists a critical point for polydispersity above which a
crystal-like shell is unstable. In a particular case of bidisperse beds, the
crystal-like shell only appears when the particle-particle friction is high enough. Finally, we compute the contact forces within particle-particle chains and in particle-wall contacts, which sustain the cylindrical shell, highlighting the dominant role of particle-particle forces.
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All authors Vinícius Pereira da Silva Oliveira, Danilo da Silva Borges, Erick de Moraes Franklin, Jorge Manuel Peixinho
Quantum Gases · Cross-listed from quant-ph
Magnetic domains stabilized by symmetry-protected zero modes
Pavel Kos, Dominik S. Wild and Kristian Knakkergaard Nielsen
Understanding mechanisms for the breakdown of thermalization in closed
quantum systems is a central problem in
quantum many-body physics. We demonstrate strong nonergodic behavior in the XX model on coupled chains, where domain-wall initial states retain an inhomogeneous magnetization profile for arbitrarily long times. We find that this effect arises due to zero modes protected by
chiral symmetry. Using an analysis based on the Lanczos
algorithm, we identify evidence for a localization transition in the thermodynamic limit at a critical coupling between the chains. We further show that
antiferromagnetic defects in the initial state and
symmetry-breaking perturbations restore slow thermalization, whereas it remains robust for
symmetry-conserving perturbations. These results establish that degenerate,
symmetry-protected subspaces can give rise to thermodynamically stable nonergodic dynamics in experimentally accessible
quantum systems.
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Materials Science
Electronic Signature of Melting Onset in Polycrystalline Copper at Extreme Conditions
Edna R. Toro, Tobias Held, Armin Bergermann et al. (+8 more)
Ultrafast melting is fundamentally a structural transition of the ionic
lattice, but this rearrangement also reshapes the electronic properties by changing the energy landscape and scattering mechanisms. Although the electrons react almost instantaneously, it is not a priori clear how much
lattice disorder is required for a significant response. Here, we show that the onset of melting already produces a clear electronic signature in polycrystalline copper. Using single-shot terahertz time-domain spectroscopy on thin films excited over a wide range of
laser fluences, we infer the transient conductivity during the first picoseconds after excitation. The data, supported by two-temperature molecular-dynamics simulations, show that before melting, electron transport is substantially limited by grain-boundary scattering and that melting strongly suppresses this channel. As melting begins at these interfaces, we observe a transient increase in the conductivity that directly marks the onset of the phase transition. More broadly, these results show that ionic and electronic relaxation stages are closely coupled in nonequilibrium
laser-driven matter and that optical measurements can resolve distinct stages of melting.
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All authors Edna R. Toro, Tobias Held, Armin Bergermann, Megan Ikeya, Maximilian Maigler, Eric R. Sung, Dirk O. Gericke, Mianzhen Mo, Baerbel Rethfeld, Siegfried H. Glenzer, Benjamin K. Ofori-Okai
Materials Science
Device-area selection of memristive transport regimes in epitaxial $Hf_{0.5}Zr_{0.5}O_{2}$-based ferroelectric devices
Priscila A. Tapia Presas, Lautaro Galarregui, Wilson Román Acevedo et al. (+5 more)
Ferroelectric memristive devices based on hafnia are promising systems for neuromorphic electronics, yet the interplay between polarization-modulated resistive changes and defect-mediated transport often leads to complex and debated switching mechanisms. Here, we investigate this competition in epitaxial Hf$_{0.5}$Zr$_{0.5}$O$_2$/La$_{0.67}$Sr$_{0.33}$MnO$_3$
heterostructures with Pt top electrodes, by combining structural, ferroelectric, and memristive characterization with a statistical analysis across a broad range of device areas spanning three orders of magnitude. We identify two distinct memristive regimes with opposite resistance-voltage chiralities. Small devices exhibit a low-resistance state that scales inversely with area, consistent with area-distributed electronic transport, while larger devices display an area-independent resistance indicative of localized conductive channels. A statistical nucleation model quantitatively captures this behavior and yields a crossover characteristic area $A^* \approx 10^3\,\mu\mathrm{m}^2$. This crossover also correlates with the onset of ferroelectric wake-up for the larger devices, linking conductive-channel nucleation and oxygen-vacancy redistribution within a unified physical picture. These results establish lateral device size as a key parameter controlling the dominant transport mechanism in epitaxial hafnia-based devices.
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All authors Priscila A. Tapia Presas, Lautaro Galarregui, Wilson Román Acevedo, Myriam H. Aguirre, José Santiso, Sylvia Matzen, Beatriz Noheda, Diego Rubi
Soft Condensed Matter
Divergence of detachment forces in the finite Voronoi model
Wei Wang and Brian A. Camley
Detachment and fracture are central to many tissue-level processes, but they are challenging to simulate with Voronoi-type models that typically assume a confluent tissue. Here we analyze the finite Voronoi model, a nonconfluent extension of conventional Voronoi models, in which
cell boundaries are composed of straight Voronoi edges and circular arcs of fixed radius $\ell$. When the line tension on
cell-medium interfaces exceeds the tension on
cell-
cell contacts, we find that the model exhibits a strong time-step dependence in the fracture timescale of initially intact active clusters: decreasing $\Delta t$ can unphysically suppress cluster rupture events. We trace this behavior to a divergence of detachment forces in the finite Voronoi model and introduce a simple regularization. We then compare the finite Voronoi model's near-detachment mechanics to a deformable polygon model and propose two potential calibration strategies. Finally, we examine the fracture–no-fracture transition in nonconfluent tissues and show that it is governed by detachment mechanics: the calibration can even determine the sign of the transition's dependence on
cell shape. Our results show that, for studies focused on fracture or intercellular adhesion in nonconfluent monolayers, a physically motivated calibration of near-detachment mechanics in the finite Voronoi model is essential.
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Disordered Systems and Neural Networks · Cross-listed from physics.med-ph
Fractal geometry-governed oxygen diffusion: Tumors vs. Normal Tissues
Neda Valizadeh, Robabeh Rahimi and Ramin Abolfath
Purpose: To develop a geometry-governed
diffusion framework that explains differential tissue response under FLASH ultra-high dose rate (UHDR) irradiation by explicitly accounting for structural heterogeneity and anomalous transport in biological tissues. Methods: We formulate a generalized
diffusion–reaction model on fractal substrates to describe molecular transport in heterogeneous media. Tissue architecture is characterized by a fractal (Hausdorff) dimension \(D\), while scale-dependent transport inefficiency and
memory effects are captured by a fractional parameter \(\theta\). Analytical solutions for radially symmetric geometries are derived and compared with classical normal (Euclidean)
diffusion and a Gaussian reference model under identical physical conditions. Transport behavior is quantified through transient probability distributions and steady-state spatial profiles. Results: The model reveals systematic suppression of long-range transport and enhanced localization as tissue structural complexity increases. Increasing \(\theta\) leads to subdiffusive dynamics, reduced effective
diffusion lengths, and persistent non-Gaussian concentration profiles, even in the steady state. While increasing \(D\) alone enhances spatial accessibility, fractional dynamics dominate transport behavior when \(\theta>0\), counteracting
geometric connectivity. These effects produce a separation between regimes characterized by efficient inter-track overlap and rapid homogenization, and regimes marked by isolated, long-lived reactive domains.
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Mesoscale and Nanoscale Physics
Simulating altermagnets using mumax+
Lars Moreels, Nicolai Bechler, Bartel Van Waeyenberge et al. (+2 more)
In this paper, we demonstrate how altermagnets can be simulated in the recently released micromagnetic simulation package mumax+. We have added a new magnet class for d-wave altermagnets and demonstrate how mumax+ is able to reproduce the analytical solutions for line profiles of the Néel vector and net magnetization for a Bloch domain wall. Next, we show simulation results of the
magnon dispersion relation and its dependence on the anisotropic nature of the exchange interaction. Finally, we study the motion of a Néel skyrmion by applying a
spin transfer torque. This new feature was implemented by extending the pre-existing code base for
antiferromagnetic simulations. The object-oriented design of mumax+ allows for a correct calculation of the magnetostatic field in multi-sublattice systems, a feature that many other micromagnetic simulators lack.
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All authors Lars Moreels, Nicolai Bechler, Bartel Van Waeyenberge, Jonathan Leliaert, Jan Masell
Quantum Gases · Cross-listed from hep-ph
Universal Description of Decoherence in Scale-Invariant Environments
Carlos Argüelles, Gabriela Barenboim, Gonzalo Herrera et al. (+2 more)
When a
quantum system couples to a scale-invariant environment, what form must its decoherence take? We prove that the answer is unique: under locality, Lorentz invariance, unitarity, and continuous scale invariance, the effect of any such environment is mathematically equivalent to that of an unparticle bath – a scale-invariant continuum of states – characterized entirely by the scaling dimension $d_{\mathcal{U}}$ of the coupled operator. This is not a modelling choice but a consequence of conformal
symmetry. All decoherence and dissipation exponents are fixed by $d_{\mathcal{U}}$ through exact consistency relations, providing falsifiable predictions independent of microscopic details. We validate the framework using multi-channel transport data from the
unitary Fermi gas, where two genuinely independent observables yield a consistent $d_{\mathcal{U}} = 7/4$. We further show that
quantum Ising criticality, inflationary cosmology, and high-energy astrophysical
neutrinos – spanning more than 25 orders of magnitude in energy – are unified as specific realizations of the same structure. A decoherence phase transition at $d_{\mathcal{U}} = 5/2$, where
quantum coherence is protected rather thandestroyed at long times, is a qualitative prediction inaccessible to any memoryless dynamical description.
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All authors Carlos Argüelles, Gabriela Barenboim, Gonzalo Herrera, Tanvi Krishnan, Héctor Sanchis
Disordered Systems and Neural Networks
The Phase Transitions in a $p$ spin Glass Model: A Numerical Study
Prerak Gupta, Auditya Sharma, Bharadwaj Vedula et al. (+2 more)
We investigate the balanced $M=4$, $p=4$
spin-glass model for a one-dimensional long-range proxy for the finite dimensional short-range $p$-
spin glass model to examine the nature of the glass transition beyond mean-field theory. We perform large-scale Monte Carlo equilibrated simulations for both fully connected and power-law diluted versions of the model. The critical temperatures extracted from the finite-size scaling (FSS) analysis of
spin-glass susceptibility are in good agreement with theoretical predictions for $\sigma = 0, 0.25$, and 0.55. For these values of the long-range exponent $\sigma$ (which is the power of the decrease of the interactions between the
spins with their separation), one might have expected that mean-field theory would provide a good description of the system. However, the
spin-overlap distribution and the value of the $\lambda$-parameter do not provide numerical evidence for a one-step replica
symmetry breaking (1RSB) phase transition. Instead, our results indicate a direct transition from the paramagnetic state to a full replica
symmetry broken phase, with a renormalized value of $\lambda\equiv \omega_2/\omega_1 < 1$ suggesting a continuous FRSB transition, despite this ratio being equal to 2 at mean-field level. A value of $\lambda > 1$ is required for the discontinuous 1RSB transition. We argue that strong finite-size effects and closely spaced transition temperatures remove the expected 1RSB transition for the system sizes which we can study. For values of the exponent $\sigma = 0.85$, which roughly corresponds to a three dimensional system, we find that the renormalized value of $\lambda$ is again less than 1, with no signs of either the 1RSB transition or the continuous FRSB transition, suggesting that the Kauzmann temperature $T_K$ in three dimensions might be zero and the complete absence of phase transitions in structural glasses.
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All authors Prerak Gupta, Auditya Sharma, Bharadwaj Vedula, J. Yeo, M.A. Moore
Statistical Mechanics · Cross-listed from hep-th
Local CFTs extremise $F$
Ludo Fraser-Taliente
Many CFTs can be extended to lines of nonlocal CFTs parametrised by the scaling dimension $\Delta$ of the fundamental field appearing in the action. $\Delta=\frac{d}{2}-\zeta$ is set by the exponent of the kinetic term $(-\partial^2)^{\zeta}$, which is nonlocal for noninteger $\zeta$. If $\Delta$ is tuned to $\Delta_\mathrm{local}$, the scaling dimension of the fundamental field in the local CFT, arXiv:1703.05325 showed that we recover the conformal data of that CFT (plus a decoupled sector). One natural question is: how is the local point special on this line of nonlocal CFTs? We prove that these local CFTs lie at the extrema of the (universal part of the) sphere free energy $\tilde{F}(\Delta)=\sin(\frac{\pi d}{2}) \log Z_{S^d}$ of the long-range CFTs: $d\tilde{F}/d\Delta|_{\Delta=\Delta_\mathrm{local}}=0$; and for
unitary CFTs they locally maximise it. The simple proof uses the fact that the derivative of $\tilde{F}$ with respect to $\Delta$ receives contributions only from the nonlocal terms in the action. The nonlocal terms must be absent in the limit $\Delta \to \Delta_\mathrm{local}$, and hence the derivative is zero. Demonstrating maximisation then requires a proof of the generalised $F$-
theorem in conformal perturbation theory to subleading order. We check our result with the O$(N)$ $\phi^4$ and cubic CFTs in the $\epsilon$ expansion and the large-$N$ limit. This result provides a minimal encoding of the scaling dimension of the fundamental field in many CFTs, and also explains the curious derivative structure of the large-$N$ expansion of $\Delta_\phi$ in the O$(N)$ model. Finally, this nonlocal $F$-extremisation can be viewed as a non-supersymmetric version of the known $c,F,a$-extremisation mechanisms.
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Mesoscale and Nanoscale Physics
Singlet-only always-on gapless exchange (SAGE) spin qubits: Charge noise effects and two-qubit gates
Nathan L. Foulk, Katharina Laubscher, Silas Hoffman et al. (+1 more)
Singlet-only always-on gapless exchange (SAGE)
spin qubits are an alternative type of exchange-only (EO)
qubits that encode a single
qubit in the
spins of four electrons located in four tunnel-coupled
quantum dots. While conventional EO
qubits are susceptible to local
magnetic field gradients caused by local
nuclear environments and $g$-factor variations, the SAGE
qubit subspace is inherently protected from
magnetic-gradient-induced Pauli errors by virtue of the singlet-only encoding, which is invariant under
magnetic field gradients, and the always-on exchange couplings, which provide energetic leakage protection. However, the always-on operation simultaneously increases the
qubit's sensitivity to charge noise. Here, starting from a Hubbard model describing the underlying electronic structure of the coupled
quantum dots, we characterize the performance of SAGE
qubits in the presence of $1/f$ charge noise that induces fluctuations in both the dot chemical potentials and the interdot tunnel couplings. We calculate SAGE idle coherence times and show that realistic CPMG-like pulse sequences can be used to significantly extend SAGE single-
qubit coherence times for experimentally relevant charge noise strengths. We likewise study the fidelity of SAGE two-
qubit gates in the presence of charge and
magnetic noise and again propose a simple refocusing strategy to mitigate the noise, while increased ramp times of the entangling pulse suppress leakage into noncomputational states.
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All authors Nathan L. Foulk, Katharina Laubscher, Silas Hoffman, Sankar Das Sarma
Strongly Correlated Electrons
Ultrastrong Coupling Signatures in Photon Statistics from Terahertz Higgs-Polaritons
Spenser Talkington, Benjamin Kass and Martin Claassen
The ultrastrong coupling regime of cavity
photons and
quantum materials has emerged as a pathway to modify materials properties, however definitive signatures of ultrastrong coupling remain elusive. Focusing on the
quantum photon statistics of light transmitted through a cavity-embedded
superconductor, we show that a two-
photon Higgs polariton at strong coupling realizes a photonic nonlinearity at the single terahertz
photon level. We find that as light-matter coupling increases, the
photon statistics show pronounced changes due to the formation of a hybrid
photon-matter dark-cavity state with finite
photon occupancy, producing testable signatures of ultrastrong coupling. We derive a non-Markovian input output relation and study the cavity-embedded
superconductor 2H-NbSe2 as it approaches ultrastrong light-matter coupling. Our results reveal a diagnostic for ultrastrong coupling in the two-
photon coincidence statistics that is absent in total counts.
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Materials Science · Cross-listed from physics.ins-det
SHIELD: A Reference Gas-Driven Permeation Platform for Hydrogen Permeation Studies
James Dark, Colin Weaver, Remi Delaporte-Mathurin et al. (+2 more)
A gas-driven permeation (GDP) platform, SHIELD (Salt-compatible Hydrogen barrier Investigation and EvaLuation for fusion Devices), has been developed to measure hydrogen transport properties in structural materials under controlled thermal and pressure conditions. The system is designed to minimise experimental uncertainties associated with leaks, temperature instability, and pressure measurement, while providing reproducible conditions for permeation experiments. The rig operates in a static GDP configuration with independent upstream and downstream volumes, enabling precise control of driving pressure and accurate measurement of downstream pressure rise. An openly documented data acquisition and processing framework is implemented to ensure data traceability and reproducibility. The platform's performance is demonstrated by hydrogen permeation measurements on 316 stainless steel and AISI 1018 low-carbon steel over the temperature range of \SIrange{100}{600}{\degreeCelsius}. Steady-state permeation fluxes are extracted from linear downstream pressure rise and used to determine permeability. The measured permeability exhibits Arrhenius behaviour and agrees well with published literature data for both materials. Permeability measurements are shown to be robust and reproducible. These results demonstrate that SHIELD provides a reliable reference platform for hydrogen permeation measurements and is well-suited to evaluating permeation barrier coatings and advanced materials for fusion applications.
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All authors James Dark, Colin Weaver, Remi Delaporte-Mathurin, Sara Ferry, Kevin B. Woller
Materials Science
Atomic-scale order enables high thermal boundary conductance at $\beta$-Ga$_2$O$_3$/4H-SiC interfaces
Hongao Yang, Yongtao Yang, Yuanbin Liu et al. (+8 more)
Thermal boundary conductance (TBC) at dissimilar interfaces imposes a fundamental limit on electronic device performance, yet predicting and understanding heat transport across realistic, disordered boundaries remains elusive. Here, we develop a computational framework that combines machine-learned interatomic potentials with
lattice dynamics to address the long-standing problem of how interfacial structure, from disordered to atomically sharp, affects thermal transport in the technologically important $\beta$-Ga$_2$O$_3$/4H-SiC
heterostructure. By explicitly accounting for
phonon wave-particle duality, we show that interfacial disorder introduces additional interfacial
phonon modes that facilitate vibrational impedance matching between the two highly dissimilar
crystals, yet it simultaneously disrupts interfacial
phonon coherence and limits the potential heat-transport benefit. Our atomistic simulations further indicate that restoring atomic-scale order preserves coherence and yields markedly higher conductance. These insights motivate the controlled epitaxial growth of $\beta$-Ga$_2$O$_3$/4H-SiC
heterostructures with systematically tuned interfacial order. Experimental measurements validate our predictions, achieving a record-high TBC of 231 MW m$^{-2}$ K$^{-1}$ at atomically sharp junctions. Beyond the immediate implications for $\beta$-Ga$_2$O$_3$-based power electronics, our results establish the preservation of interfacial
phonon coherence as an effective strategy for mitigating thermal bottlenecks in mismatched systems.
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All authors Hongao Yang, Yongtao Yang, Yuanbin Liu, Tao Ding, Yang Shen, Jiawei Huang, Weigang Ma, Linfeng Fei, Zhenping Wu, Gábor Csányi, Bingyang Cao
Disordered Systems and Neural Networks · Cross-listed from astro-ph.CO
Gravitational-wave lensing beyond rays: a disordered-system approach
Ripalta Amoruso, Ginevra Braga, Alice Garoffolo et al. (+3 more)
We develop a framework to describe gravitational wave propagation through a
stochastic distribution of weak gravitational lenses beyond the
geometric optics limit. We model the lens distribution as a static random background field and formulate the problem in the
language of quenched disorder, treating the disorder averaged density
matrix as the fundamental object from which observables are computed. Using the Schwinger Keldysh formalism, we construct a path-integral representation of the averaged density
matrix and derive its explicit form perturbatively for a suitable class of couplings. The result naturally separates into a quadratic exponential term, which governs the suppression of phase sensitive contributions in the averaged description, and a purely oscillatory contribution, which modifies coherent propagation through a disorder-induced correction to the propagation kernel. This provides a unified description of interference, diffraction, and statistical fluctuations of the lens distribution within a single framework. We also identify the physical scales controlling the onset of coherence loss and illustrate the formalism in the case of Gaussian wave packets. More generally, the derivation applies to any system described by the same class of actions, making the framework relevant beyond gravitational wave
lensing to wave propagation in disordered media.
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All authors Ripalta Amoruso, Ginevra Braga, Alice Garoffolo, Francescopaolo Lopez, Nicola Bartolo, Sabino Matarrese
Statistical Mechanics · Cross-listed from physics.flu-dyn
Superstatistical Approach to Turbulent Circulation Fluctuations
Henrique S. Lima, Rodrigo M. Pereira, Luca Moriconi et al. (+2 more)
Recent investigations of turbulent circulation fluctuations have uncovered substantial insights into the statistical organization of flow structures and revealed unexpected
geometric features of turbulent intermittency. Of particular interest here is the observation that circulation probability distribution functions admit a superstatistical representation, namely a description based on "ensembles of Boltzmann-Gibbs ensembles". A fundamental phenomenological ingredient of this approach, which serves as a natural starting point for modeling, relies on the strong correlation between the dissipation field and the spatial distribution of elementary circulation-carrying structures, i.e., small-scale
vortices. Within the
language of superstatistics, this corresponds to characterizing circulation statistics through an appropriate choice of conditioned (Boltzmann-like) distributions and mixing distributions. We show that the superstatistical class of q-exponentials, known to have broad applicability in a wide range of multiscale and non-
equilibrium systems, provides an accurate description of the observed circulation statistics in homogeneous and isotropic
turbulence. This finding opens avenues for exploring the statistical structure of the turbulent cascade in the context of non-extensive statistical mechanics, rooted in the concept of non-additive
entropies.
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All authors Henrique S. Lima, Rodrigo M. Pereira, Luca Moriconi, Katepalli R. Sreenivasan, Constantino Tsallis
Mesoscale and Nanoscale Physics
New frontiers in quantum science and technology using van der Waals Josephson junctions
Joydip Sarkar, Ayshi Mukherjee, Amit Basu et al. (+3 more)
Over the last decade, the development of Josephson devices based on van der Waals (vdW) materials has advanced rapidly, representing a paradigm shift driven by the advent of 2D materials. The diverse vdW materials library, combined with advanced fabrication techniques, enables the integration of materials with vastly disparate properties for scientific exploration. The vdW Josephson junctions (JJs) offer a unique route to explore novel functionalities and associated physics that remain inaccessible in conventional JJs, which have reached an industrial level in terms of fabrication. Beyond material diversity, vdW crystalline materials offer fundamental new control over device
symmetries, enabling the realization of
Hamiltonians unique to 2D systems. Furthermore, the long relaxation times of myriad excitations in 2D
heterostructures open possibilities for creating exquisite
quantum sensors, with the 2D material itself acting as an efficient bus for transmitting excitations to the active sensing element. This creative explosion in vdW-based superconducting electronics is rapidly growing, and our review highlights the resulting devices and physics. The confluence of vdW JJs with twistronics and
topology has the potential to redefine superconducting
quantum technology, enabling applications from
quantum computation to ultra-sensitive hybrid sensors. While opportunities abound with vdW JJs, the challenge of scalability must be surmounted for translation into real-world devices. This review synthesizes current developments and offers a roadmap for researchers navigating this burgeoning field.
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All authors Joydip Sarkar, Ayshi Mukherjee, Amit Basu, Ritajit Kundu, Arijit Kundu, Mandar M. Deshmukh
Statistical Mechanics · Cross-listed from quant-ph
Assembling Extensive Quantum Fisher Information in Stabilizer Systems
Arnau Lira-Solanilla, Sreemayee Aditya, Xhek Turkeshi et al. (+1 more)
We introduce a systematic framework to construct nonlocal observables with extensive
quantum Fisher information (QFI) density in stabilizer codes. The construction maps stabilizer generators to dual Ising
spins whose correlators equal string order parameters, converting hidden nonlocal order into a metrologically accessible observable. Applying this to monitored cluster codes and the toric code, we identify transitions in the QFI scaling from an extensive regime, where long-range string order prevails, to an intensive one driven by competing single-site measurements.
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All authors Arnau Lira-Solanilla, Sreemayee Aditya, Xhek Turkeshi, Silvia Pappalardi
Strongly Correlated Electrons
Universal magnetic energy scale in the doped Fermi-Hubbard model
Radu Andrei, Ivan Morera, Jonathan B. Curtis et al. (+2 more)
Magnetic correlations of doped Mott
insulators hold the key to the unusual characteristics of many
quantum materials. Recent experiments with ultracold atoms in optical
lattices have provided new information about the
magnetic properties of the
Fermi-Hubbard model on a square
lattice. We demonstrate that recent measurements indicate that a single doping-dependent energy scale determines both static correlations and dynamical response of these systems. To understand these experimental findings, we employ a self-consistent formalism to describe the coupling between
antiferromagnetic magnons and doped holes, and we uncover the emergence of a universal
magnetic energy scale at finite doping, which we denote by $J^*$. We present the single- and two-
magnon spectral properties at finite doping and discuss the appearance of a bimagnon peak in
lattice-modulation spectroscopy, at frequencies set by $J^*$. Furthermore, we argue that this same energy scale sets the onset of pseudogap phenomena, leading to the hypothesis $k_BT^* = c J^*$, with $c$ an order one number. We identify another low-energy scale emerging from our analysis of
magnetic excitations, and argue that it controls the stability of Néel order at the lowest temperatures, ultimately driving a transition to an incommensurate
spin-density-wave at finite doping. We discuss the relation between this low-energy scale and the nature of fermionic quasiparticles. Our analysis suggests that stability of the commensurate antiferromagentic phase at finite doping can be controlled experimentally by introducing additional quasiparticle broadening via disorder or low-frequency noise.
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All authors Radu Andrei, Ivan Morera, Jonathan B. Curtis, Immanuel Bloch, Eugene Demler
Mesoscale and Nanoscale Physics · Cross-listed from quant-ph
Simulation of quantum annealing on a semiconducting cQED device for Multiple Hypothesis Tracking (MHT) benchmark
Quentin Schaeverbeke, Viktor Radović, Jean-Marc Divanon et al. (+1 more)
We explore the expected performance of a semiconducting
spin cQED
quantum processor for Multiple Hypothesis Tracking (MHT)
algorithm via a
quantum annealing procedure. From two different benchmarking scenarios we evaluate this type of
quantum annealer on a
quantum emulator in which we incorporated both dynamical coherent errors and incoherent errors. From estimate of the reset, measurement and annealing time of the processor, we find that cQED-
spin processors could reach a total run time of around 50 ms. This makes this technology promising for potential real time application such as radar tracking.
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All authors Quentin Schaeverbeke, Viktor Radović, Jean-Marc Divanon, Bing Hong Teh
Soft Condensed Matter
Orientational bistability and field-controlled switching of a superparamagnetic dimer
James R. N. Tett, Finlay Johnston, Brennan Sprinkle et al. (+1 more)
We study the orientational dynamics of superparamagnetic colloidal dimers that carry both an induced
magnetic moment, proportional to the applied field, and an effective permanent moment. In a static, uniform
magnetic field, dimers that are permanently fixed together hop between two preferred in-plane angles, developing a bimodal steady-state orientation distribution. When the same field is periodically reversed, we observe a sharp, field-controlled change in the dynamical response from small hopping events with $\Delta \theta\ll \pi$ to full $\Delta\theta \approx \pi$ rotations on each field flip. We show that both the static bistability and the switching bifurcation can be rationalised by a
magnetic response in the dimer that consists of both a strong induced and weak body-fixed component. This leads to a complex orientational energy/potential landscape, with coupled roll-yaw rotations of the dimer responsible for the bistable dynamics. By combining the misorientation between dimer axis and field, bifurcation field strength and short-time orientational variance, we determine the magnitude and orientation of the net permanent dipole, thereby characterising details of the internal
magnetic structure of the particles via microscopy.
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All authors James R. N. Tett, Finlay Johnston, Brennan Sprinkle, Alice L. Thorneywork
Materials Science · Cross-listed from physics.app-ph
3D Finite Element-Based Multiphysics Simulation of a Shape Memory Alloy Hybrid Composite Module
Lukas Handl, Max Kaiser, Miro Duhovic et al. (+1 more)
Shape adaptive shape
memory alloy hybrid composites (SMAHCs) are composites that incorporate shape
memory alloys (SMAs) to realize shape transformation. Despite the availability of numerous analytical and finite element models for predicting the transient response of SMAHCs, many approaches exhibit limitations with respect to the thermomechanical coupling and comprehensive experimental validation. Therefore, this paper presents a coupled, multiphysics, 3D finite element approach for the simulation of a SMAHC actuator, integrating mechanical, thermal and electromagnetic solvers in the Finite Element Code ANSYS LS-DYNA. The proposed approach employs a micromechanical constitutive model implemented in ANSYS LS-DYNA, to accurately capture the complex thermomechanical phase transformation of SMAs. A key feature of the model is the ability to prescribe a defined martensitic pre-strain through a preceding simulation step, in which an initially scaled SMA wire is mechanically loaded and stretched to its nominal length. This procedure enables partial detwinning of the martensitic microstructure and provides a physically motivated initialization of the material state. Joule heating of the SMA wires, as well as varying mechanical loads and ambient temperature conditions, are explicitly considered. The simulation results are validated against experimental data and a fully coupled transient staggered scheme model to assess the predictive capability of the 3D approach. The results show good qualitative agreement, reproducing the characteristic hysteresis of actuator deflection as a function of temperature. Quantitatively, the predicted deflections are of the correct order of magnitude, although marginally outside the 95 % experimental confidence interval. Overall, a consistent trend between simulation and experiment is observed, giving rise to possibility of simulating more complex SMAHC systems.
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All authors Lukas Handl, Max Kaiser, Miro Duhovic, Martin Gurka
Superconductivity
A. A. Mazanik and F. S. Bergeret
We study the penetration of an external
magnetic field into a
superconductor with collinear $d$-wave altermagnetic order. We demonstrate that instead of circular Abrikosov
vortices, the
magnetic field generates elliptical
vortices with their major axis oriented along one of the crystallographic axis, along which the altermagnetic
spin splitting is maximal. Upon reversing the component of the
magnetic field parallel to the altermagnetic Néel vector, the
vortices reorient towards the other crystallographic axis with maximal
spin splitting. We demonstrate that this effect originates from an altermagnetism-induced anisotropy of the effective mass, which is controlled by the coupling between the external
magnetic field and the Néel vector. As a consequence, a superconducting film hosting such altermagnetic order and containing pinning defects exhibits nonreciprocal magnetization curves under reversal of the
magnetic field parallel to its Néel vector, due to the different
vortex–
vortex interaction energies for the two field orientations. Our results broaden the understanding of the coexistence of altermagnetism and superconductivity, both in materials hosting these orders intrinsically or in
superconductor/altermagnet hybrid structures, and open new experimental avenues for exploring supercurrent
vortices in these systems.
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Materials Science
Optimal spin-qubit hallmarks of sulfur-vacancy defects in 4H-SiC: Design from first principles
Marisol Alcántara Ortigoza and Sergey Stolbov
By applying our methodology, we propose a defect in 4H-SiC which combines a Si vacancy and a C atom substituted with S (VSiSC) to have a
spin-triplet ground state with the
spin qubit functionality. Our calculations confirm that all configurations of the defect have a dynamically and thermodynamically stable triplet ground state and higher energy singlet states, essential for the
spin-
qubit polarization cycle. From GW calculations, we found that the electronic states associated with the defect form sharp and isolated peaks within the band gap for both triplet and singlet states. Further Bethe-Salpeter-equation calculations show that all considered configurations have intense optical excitations in the near infrared spectrum range. Analysis of the excitation energies and rates indicate that the VSiSC defect can be an excellent optically controlled
spin qubit. Crucially, the host elements and the dopant have high-abundance isotopes with zero
nuclear spin ensuring high
spin-coherence time of the
qubit.
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Materials Science
Lattice dynamics and complete polarization analysis of Raman-active modes in LaInO$_3$
Jonas Rose, Hai Nguyen, Moritz Meißner et al. (+7 more)
In this study, we present a comprehensive analysis of the Raman active
phonon modes in orthorhombic LaInO$_3$ based on a combination of polarization-angle resolved Raman spectroscopy and density functional theory calculations. By using backscattering from multiple crystallographic surface orientations and employing a full
symmetry analysis, we identify and assign most of the Raman-active $\Gamma$-point
phonons to their irreducible representations of the D$_{\rm{2h}}$ point group. A multidimensional hyperspectral fitting procedure allows us to extract the relative Raman tensor elements from the angular dependence of the scattering intensities, even for strongly overlapping modes. First-principles calculations yield the
phonon dispersion along high-
symmetry directions, the
phonon densities of states, and atomic displacement patterns, which are found to be in good agreement with the experimental mode frequencies.
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All authors Jonas Rose, Hai Nguyen, Moritz Meißner, Zbigniew Galazka, Roland Gillen, Georg Hoffmann, Oliver Brandt, Manfred Ramsteiner, Markus R. Wagner, Hans Tornatzky