Mesoscale and Nanoscale Physics · Cross-listed from quant-ph
Exploring dynamics of individual vortices in a superconductor via a levitated magnetic transducer
Yiqi Wang, Trisha Madhavan, J. DaLi Schaefer et al. (+3 more)
Trapped
vortices determine fundamental properties of
superconductors and play an important role in many practical applications such as
magnetic levitation, however their complex dynamics remain poorly understood. Here, we use the mechanical motion of micron-scale levitated
magnetic particles to probe the dynamics of individual
vortices. Specifically, we show that the dynamics of levitated magnets are strongly influenced by
vortices trapped in the YBCO superconducting film. We observe random telegraph signals in the mechanical frequency, dissipation rate, and energy of levitated particles, which we attribute to random tunneling of individual
vortices. The nonlinearity of
vortex-defect interaction manifests as non-exponential decay in ringdown measurements, revealing a complex underlying potential landscape. Our results provide insights into elusive dissipation mechanisms in superconducting levitated systems, open new avenues for using levitated magnets as sensitive probes of static and dynamic properties of individual
vortices in
superconductors and their interactions with material disorder, and point toward novel routes for using
magnetic particles as highly coherent mechanical transducers.
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All authors Yiqi Wang, Trisha Madhavan, J. DaLi Schaefer, Addison NewRingeisen, Frankie Fung, Mikhail D. Lukin
Soft Condensed Matter
Weak-Flow Induced Dielectric Axes Rotation in Dipolar Suspensions
Pramodt Srinivasula
Conventional rheodielectric studies of dipolar suspensions primarily examine flow-induced variations in the principal permittivity components. In contrast, an asymptotic solution of the perturbed Fokker–Planck equation for orientable Brownian dipoles under weak flow predicts the emergence of off-diagonal permittivity components that are linear in the relative flow strength. For planar shear flow, these terms exceed the corresponding higher-order diagonal corrections, leading to a rotation of the principal dielectric axes. This previously unrecognized rheodielectric response suggests new possibilities for flow-controlled dielectric and electro-optical functionalities.
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Mesoscale and Nanoscale Physics
Strong coupling between propagating spin wave and microwave photons in a superconducting resonator
Yi Li, Jinho Lim, Xingzhi Wang et al. (+12 more)
We demonstrate strong coupling between propagating
spin wave modes and microwave
photons in superconducting resonator-
magnetic thin film hybrid
circuits. By fabricating the resonator directly on yttrium iron garnet thin films grown on rare-earth-free Y$_3$Sc$_2$Ga$_3$O$_{12}$ substrates, we achieve strong coupling of both Damon-Eshbach and backward-volume
spin wave modes to the resonator, with coupling strengths exceeding both the
magnon and
photon damping rates. Furthermore, we observe nonreciprocal
spin wave radiation of the hybrid magnonic mode in the Damon-Eshbach configuration, highlighting the potential for incorporating intrinsic
spin-wave nonreciprocity into hybrid magnonic systems. These results open new avenues for integrating
spin-wave magnonics with cavity magnonics, and for harnessing
spin waves for potential applications in
quantum information science.
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All authors Yi Li, Jinho Lim, Xingzhi Wang, Tomas Polakovic, Carissa Kiehl, Moojune Song, Phuoc Cao Van, Ralu Divan, Ulrich Welp, Charudatta Phatak, Jong-Ryul Jeong, Kab-Jin Kim, Jian-Min Zuo, Axel Hoffmann, Valentine Novosad
Statistical Mechanics
Field theories for Laplacian Growth
Paolo Pisapia, Assaf Shapira and Kay Joerg Wiese
Loop-erased random walks (LERW), the $O(n)$-model at ${n=-2}$ and
Laplacian random walks (LRW) are three realizations of the same random process. While this equivalence holds on any graph, renormalization is possible only via the $O(-2)$-model. To generalize LRWs to $b$-LRWs or to
Diffusion Limited Aggregation (DLA), a field theory directly on the
Laplacian growth process is necessary. Here we construct an exact
lattice action for LRWs and show that its perturbative expansion equals that of LERWs. We then generalize this approach to $b$-LRWs and DLA.
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Materials Science
Investigation on the temperature dependence of substrate-induced in-plane uniaxial magnetic anisotropy in Ni thin films grown on 128{\deg} Y-cut LiNbO3
Kalani Perera, Morton Greenslit, Luke Doucette et al. (+2 more)
We report the temperature dependence of the substrate-induced
magnetic anisotropy in continuous Ni thin films deposited at room temperature using magnetron sputtering on a 128{\deg} Y-cut LiNbO3 substrate. Ultrathin films exhibit a pronounced temperature dependence in magnetization, with as-grown films showing isotropic behavior and an unconventional hysteresis branch crossing at relatively low temperatures, whereas no branch crossing is observed in annealed films over the investigated temperature range, indicating suppression of the underlying mechanism. Temperature-dependent magnetization measurements show that post-deposition annealing establishes uniaxial anisotropy with well-defined easy and hard axes, whose strength evolves with temperature due to the nature of residual strain governed by both
lattice mismatch and coefficient of thermal expansion (CTE) mismatch between the Ni film and the 128{\deg} Y-cut substrate, independent of film thickness for both 5 nm and 100 nm films. The emergence of this anisotropy following annealing indicates enhanced magnetoelastic coupling at the film-substrate interface, as the
magnetic response begins to follow the anisotropic strain imposed by
lattice mismatch and CTE mismatch.
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All authors Kalani Perera, Morton Greenslit, Luke Doucette, Mauricio Pereira da Cunha, Nicholas S Bingham
Quantum Gases · Cross-listed from quant-ph
Quantum computer architecture with ions in tweezer arrays
Benjamin F. Schiffer, Christopher Monroe, Peter Zoller et al. (+1 more)
We propose a
quantum computer architecture based on ions confined in optical tweezer arrays, combining the long coherence times of trapped-ion
qubits with the reconfigurability and parallel operation enabled by tweezer platforms. Selected ions are transported to local interaction zones, where excitation to an auxiliary state with a displaced optical potential generates a controllable effective electric dipole. We develop and analyze entangling-gate mechanisms mediated by the Coulomb interaction between such effective dipoles, and show that they enable precise, temperature-robust closure of the center-of-mass and relative motional trajectories, leaving no residual
entanglement between the
qubits and the motion. We further outline a concrete implementation with barium ions based on state-selective polarizability, and study the suppression of cross-talk during parallel gate execution, with relevance to transversal gates in
quantum error correction. Our results thereby establish a realistic route toward scalable ion-tweezer
quantum processors.
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All authors Benjamin F. Schiffer, Christopher Monroe, Peter Zoller, J. Ignacio Cirac
Soft Condensed Matter
Light selects non-equilibrium states of phase-separated droplets
Zi Lin, Thomas Beneyton, Suzanne Lafon et al. (+5 more)
Driving phase-separated droplets out of
equilibrium can oppose coarsening and trigger division. Selecting and sustaining these distinct states remains an important experimental challenge. Here, we use reversible photoswitching to tune molecular driving in DNA-azobenzene coacervates confined in microfluidic droplets without chemical fuel depletion or waste accumulation. Single-wavelength illumination sustaining bidirectional molecular switching arrests droplet coarsening at a finite size. Dual-wavelength illumination with wavelength-dependent penetration depths generates spatially asymmetric molecular driving within uniformly illuminated droplets, producing persistent interfacial instabilities. Under low-salt conditions, droplets divide and undergo recurrent growth-division cycles. Kinetic and thermodynamic measurements reveal how flux balance, phase stability and droplet size govern these distinct non-
equilibrium states. These findings establish optically controlled molecular driving as a route to selecting sustained non-
equilibrium droplet dynamics.
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All authors Zi Lin, Thomas Beneyton, Suzanne Lafon, Edison Rafael Jimenez Granda, Liangfei Tian, Alexandre Baron, Jean-Christophe Baret, Nicolas Martin
Soft Condensed Matter
Organic Semiconductor Alignment via Confinement in Vapor-Guided Droplets
Robert Malinowski, Alessandro Rossi, Lewis M. Cowen et al. (+8 more)
Organic
semiconductors are lightweight, solution-processable materials with strong potential for printed and flexible electronics, from deformable displays to wearable sensors. Despite significant advances in materials synthesis and manufacturing, controlling molecular and mesoscale
alignment during deposition remains a central challenge, as film morphology critically governs charge transport and device performance. Here, we demonstrate that flows developing within the intrinsically confined volume of microliter vapor-guided droplets can be harnessed to produce highly aligned organic
semiconductor films. As droplets move in response to an external vapor source, internal flows align organic semiconducting nanowires within the droplet prior to deposition, yielding films with pronounced directional order. Organic field-effect transistors fabricated with this approach exhibit approximately 40% enhancement in saturation current relative to
spin-coated controls. Beyond improved device performance, the contactless and compact nature of our method enables the deposition and
alignment of organic
semiconductors on curved and flexible surfaces. More broadly, vapor-guided droplets offer a scalable framework for the confinement-induced
alignment of functional soft materials, with potential for integration into existing additive manufacturing platforms for flexible electronics and beyond.
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All authors Robert Malinowski, Alessandro Rossi, Lewis M. Cowen, Peter A. Gilhooly-Finn, Michael A. Parkes, Ming-Hao Chang, Yu-Cheng Chiu, Ioannis Papakonstantinou, Matthew O. Blunt, Bob C. Schroeder, Giorgio Volpe
Strongly Correlated Electrons
Finite temperature precursors of Mottness in the Fermi Hubbard model
Sayantan Roy, Abhisek Samanta and Nandini Trivedi
We investigate finite-temperature precursors of Mottness in the repulsive Hubbard model above the
spin-ordering temperature, using numerically exact determinant
quantum Monte Carlo. We show that the finite-temperature crossover is accompanied by a pronounced suppression of charge fluctuations, despite the presence of a gapless single-particle spectra, demonstrating that Mottness first emerges via two-particle response in an anomalous metallic regime, before appearing in single-particle spectral functions. We further show that a gap formation in the density of states occurs through momentum-resolved redistribution of spectral weight across the Brillouin zone, that begins at the onset of anomalous metallic regime, rather than through gap formation in single-particle spectral functions at individual momenta. Upon doping, the anomalous-metallic regime generates transport and spectroscopic signatures characteristic of doped Mott
insulators. This shows that the transport and spectroscopic anomalies of the doped Hubbard model do not require the presence of a fully formed Mott
insulator at half-filling, but instead originate from the strong charge-response renormalization and spectral-weight redistribution that develop within the precursor anomalous metallic regime at half-filling.
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Statistical Mechanics
An integrable approach to macroscopic fluctuation theory for the multispecies SSEP
Luigi Cantini
We study the macroscopic fluctuation theory (MFT) of a multispecies generalization of the symmetric simple exclusion process (mSSEP) on the infinite line, in which particles of $N+1$ species – including, possibly, a vacancy species – exchange positions at unit rate. Working with the full, redundant set of coarse-grained densities $\bfrho=\{\rho_0,\dots,\rho_N\}$ keeps the relabelling
symmetry of the model manifest throughout. We first extend the argument of Derrida and Gerschenfeld to the multispecies setting, showing that the cumulant generating function of the multispecies current between two regions of an arbitrary graph depends on the boundary densities $ \bfrho_L,\bfrho_R$ and on the fugacities $\bflambda$ only through a single scalar variable $\omega$. We then formulate the MFT saddle-point equations for the mSSEP on the infinite line and show that they define an integrable system: they are of Landau–Lifshitz type, and a Zakharov–Takhtajan gauge transformation recasts them in AKNS form. Solving the resulting linear scattering problem by the inverse scattering method, we recover the cumulant generating function $F(\omega)$ for the multispecies current, as well as the initial and final density profiles conditioned on a prescribed current fluctuation. In particular, we show that $F(\omega)$ coincides with the function obtained by Derrida and Gerschenfeld for the single-species SSEP, now derived for an arbitrary number of species directly from the integrable structure of the multispecies MFT equations.
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Materials Science · Cross-listed from quant-ph
From Approximate Floquet Engineering to Full Floquet Theory: Coherent Control of Chiral Spin Systems in Spintronics
Andrea Simion, Claudiu Filip and Coriolan Tiusan
Coherent control of interacting
spin systems under time-periodic driving is a central challenge in
spin-based
quantum technologies. Here we demonstrate the applicability of a full Floquet-space formalism, adapted from
Nuclear Magnetic Resonance (NMR) methodologies, to model the dynamics of driven coupled electron
spins in the presence of a static
magnetic field B0 and a transverse oscillating field B1. The framework explicitly includes isotropic exchange coupling J and the
chiral Dzyaloshinskii-Moriya antisymmetric exchange interaction (DMI), and its numerical convergence is systematically validated with respect to
Fourier-space truncation. In the non-interacting limit, the expected driven-
spin dynamics is recovered, with the oscillation periodicity governed by B1. Exchange coupling alone does not modify the collective
spin expectation values under the chosen initial condition, consistent with
symmetry considerations. In contrast, increasing DMI generates a finite Sy component, suppresses Sz, and produces tilted, elliptical Bloch-sphere trajectories, reflecting the emergence of
chiral spin-
spin correlations. These effects are pronounced for open boundary conditions, while remaining nearly negligible in the periodic boundary case. When exchange coupling and DMI coexist, the dynamics becomes strongly perturbed and multi-frequency in nature. Together, these results demonstrate that full Floquet-space modeling provides a robust and predictive framework for analyzing and engineering coherent dynamics in driven interacting
spin systems beyond simple coherent-rotation regimes.
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Mesoscale and Nanoscale Physics
Phase-Shifted Planar Hall and Magnetoresistive Responses in Weyl Semimetals
Sandip Bera and Sudhansu S. Mandal
The planar
Hall resistivity and magnetoresistivity of Weyl semimetals are conventionally expected to exhibit $\sin 2\phi$ and $\cos2\phi$ angular dependences, respectively, where $\phi$ is the angle between electric and
magnetic fields. However, experiments reveal shifted extrema in the planar
Hall signal and sign reversals in magnetoresistivity at $\phi < \pi/4$. Here, using a diagrammatic Kubo-formula approach, we identify an intrinsic quadratic
magnetic-field contribution to the planar transport response that is absent in conventional semiclassical description. This contribution introduces an additional term proportional to $\cos 2 \phi$ and $\sin 2\phi$, respectively, in transverse and longitudinal conductivities. Consequently, both planar
Hall and magnetoresistive responses acquire a phase-shifted form $\sin 2(\phi+\phi_r)$ and $\cos 2(\phi+\phi_r)$, respectively. The same phase shift extracted independently from longitudinal and transverse responses quantitatively describes available experimental data. Our results establish a microscopic origin of the anomalous angular dependence observed in Weyl semimetals.
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Soft Condensed Matter
Unraveling Internal Friction in a Coarse-Grained Protein Model
Carlos Monago, J. A. de la Torre, Rafael Delgado-Buscalioni et al. (+1 more)
Understanding the dynamic behavior of complex biomolecules requires simplified models that not only make computations feasible but also reveal fundamental mechanisms. Coarse-graining (CG) achieves this by grouping atoms into beads, whose
stochastic dynamics can be derived using the Mori-Zwanzig formalism, capturing both reversible and irreversible interactions. In
liquid, the dissipative bead-bead interactions have so far been restricted to hydrodynamic couplings. However, friction does not only arises from the solvent but notably, from the internal degrees of freedom missing in the CG beads. This leads to an additional ”internal friction” whose relevance is studied in this contribution. By comparing with all-atom molecular dynamics (MD), we neatly show that in order to accurately reproduce the dynamics of a globular
protein in water using a coarse-grained (CG) model, not only a precise determination of elastic couplings and the Stokesian self-friction of each bead is required. Critically, the inclusion of internal friction between beads is also necessary for a faithful representation of
protein dynamics. We propose to optimize the parameters of the CG model through a self-averaging method that integrates the CG dynamics with an
evolution equation for the CG parameters. This approach ensures that selected quantities, such as the radial distribution function and the time correlation of bead velocities, match the corresponding MD values.
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All authors Carlos Monago, J. A. de la Torre, Rafael Delgado-Buscalioni, Pep Español
Materials Science
Connection between the GKSL master equation and the Landauer formula
Misa Nozaki and Takatoshi Fujita
We derive a current formula within the Gorini-Kossakowski-Sudarshan-Lindblad (GKSL) master equation formalism for a non-interacting system, and identify the conditions under which it reduces to the Landauer formula.
Mesoscale and Nanoscale Physics
Magnetoresistance in chiral systems driven by inter-band spin-orbit coupling
Misa Nozaki and Takatoshi Fujita
Chiral-induced
spin selectivity (CISS), in which electrons transmitted through nonmagnetic
chiral materials exhibit strong
spin-dependent transport, has attracted growing interest for spintronic applications. However, a quantitative understanding of CISS remains elusive, partly because most previous studies rely on single-band models. In this work, we theoretically investigate multi-band effects on magnetoresistance (MR)-CISS, which is typically observed in experiments using
magnetic conductive atomic force microscopy. To evaluate the
spin polarization in MR-CISS, we simulate the nonequilibrium steady-state current using the Gorini-Kossakowski-Sudarshan-Lindblad master equation. We find that
spin polarization exceeding 25% can be achieved for realistic inter-band
spin-orbit coupling strengths in the presence of on-site Coulomb interactions. These findings highlight the crucial role of inter-band
spin-orbit coupling in the mechanism of CISS.
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Mesoscale and Nanoscale Physics
Low-energy model for doped graphene nanoribbons
J. Ferrer, A. García-Fuente, Y. Yang et al. (+2 more)
We analyse in this article the many-body behavior of free-standing doped
graphene nanoribbons where the chemical potential lies inside the bulk single-particle bands. We perform an exact mapping from both an extended and an on-site Hubbard model of the ribbons to a Kanamori model, which includes
ferromagnetic exchange and pair-hopping interactions. We determine the resulting Coulomb
matrix elements analytically, and identify their scaling behavior as a function of ribbon width and length. We propose a low-energy version of the Kanamori
Hamiltonian to address the response of the ribbons to external fields, with a view to their use as transport channels in nanoelectronics. We find that the model and the proposed ribbon parameters can produce open-shell, high-
spin many-body states that can lead to shell- and
spin-blockade responses.
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All authors J. Ferrer, A. García-Fuente, Y. Yang, S. Volosheniuk, H.S.J. van der Zant
Mesoscale and Nanoscale Physics · Cross-listed from physics.optics
Observation of Non-Hermitian Skin Dynamics in the Liouvillian Regime
Shu Yang, Yeyang Sun, Lingrui Hong et al. (+1 more)
Open
quantum systems generally do not perfectly preserve phase coherence: coupling to uncontrolled environments requires a density-
matrix description based on the Liouvillian framework beyond pure-state wave
evolution. Realizing and probing such dynamics in a programmable platform is therefore essential for connecting coherent physics to realistic dissipative settings. Here we implement a tunable open-system
quantum walk in a photonic mesh
lattice, where controlled phase noise produces adjustable dephasing and non-reciprocal gain-loss imbalance provides an independently tunable non-Hermitian drive. This allows us to continuously interpolate between coherent
quantum walks and incoherent classical walks, and to observe how directional transport evolves in the Liouvillian regime. Using non-Hermitian skin dynamics as a probe, we measure the center-of-mass drift over both the coherence and non-Hermiticity parameters, revealing a crossover from coherence-enhanced to decoherence-enhanced transport in quantitative agreement with
quantum-channel simulations. We further program spatial and temporal interfaces to demonstrate interface accumulation and a long-time drift governed by the instantaneous channel. Our results establish a controllable photonic platform for simulating open
quantum dynamics and show that decoherence can actively reshape non-Hermitian transport.
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All authors Shu Yang, Yeyang Sun, Lingrui Hong, Yi Yang
Superconductivity
High temperature transitions in Ruddlesden-Popper nickelates La$_{n+1}$Ni$_{n}$O$_{3n+1}$
P. Reiss, A. Shevchenko, P. S. Lizama et al. (+9 more)
The discovery of superconductivity at $15\,\mathrm{K}$ in the infinite-layer nickelate $(\mathrm{Nd},\mathrm{Sr})\mathrm{NiO}_2$, followed by superconductivity at $80\,\mathrm{K}$ in the Ruddlesden–Popper phase $\mathrm{La}_3\mathrm{Ni}_2\mathrm{O}_7$, has ushered in a new era of nickelate research. Despite this progress, large discrepancies between reports exist. Here, we investigate the complete series of bulk-stable $\mathrm{La}_{n+1}\mathrm{Ni}_n\mathrm{O}_{3n+1}$ compounds using a comprehensive set of experimental techniques, including PXRD, single-
crystal XRD, electron microscopy, heat capacity, differential scanning calorimetry,
magnetic susceptibility, and transport measurements, over a broad temperature range from $2$ to $1000\,\mathrm{K}$. By studying high-quality single
crystals, we identify a previously underappreciated high-temperature phase transition in Ruddlesden–Popper nickelates $\mathrm{La}_{n+1}\mathrm{Ni}_n\mathrm{O}_{3n+1}$ distinct from the one going to a tetragonal phase.
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All authors P. Reiss, A. Shevchenko, P. S. Lizama, J. Nuss, R. Dinnebier, P. A. van Aken, M. Hepting, M. Isobe, Y. E. Suyolcu, H. Takagi, B. Keimer, P. Puphal
Mesoscale and Nanoscale Physics · Cross-listed from physics.optics
In-plane vector-field imaging of propagating surface phonon polaritons
Richarda Niemann, Dorothée S. Mader, Gonzalo Alvarez-Pérez et al. (+9 more)
Polariton interferometry through optical near-field microscopy has become a powerful tool in nanophotonics, enabling direct spatial access to the propagation characteristics of strongly confined, evanescent polariton modes. Scattering-type near-field optical microscopy has matured as the
prime tool for such studies, yet mostly the out-of-plane components of the optical near fields are probed, owing to the elongated geometry of the nanotip. Here, we demonstrate a complementary far-field nonlinear microscopy approach which allows to selectively probe in-plane polariton field components. Accessing the full vector field is interesting when studying complex mode patterns such as
hyperbolic polaritons or skyrmions, where the in-plane field components are typically only inferred from the out-of-plane component but not measured directly. To this end, we use nonlinear infrared-visible wide-field sum-frequency generation microscopy, where the short visible wavelength of the nonlinear signal provides the high spatial resolution to access evanescent modes in the infrared. The
symmetry selection rules of the nonlinear process further enable polarization-selective imaging of both in-plane polariton field components through spatial interferometry. The concept is demonstrated experimentally using surface
phonon polaritons at the AlN-air interface launched by a gold
antenna. A simple, semi-analytical model reproduces the peculiar propagation patterns. Hyperspectral imaging with a tunable narrowband
laser further gives access to the polariton dispersion. The wide-field methodology holds high promise for in-depth and high-throughput studies of infrared nanophotonic structures.
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All authors Richarda Niemann, Dorothée S. Mader, Gonzalo Alvarez-Pérez, Ana I. F. Tresguerres-Mata, Aitana Tarazaga Martín-Luengo, Stefan Partel, Joshua D. Caldwell, Niclas S. Mueller, Martin Wolf, Javier Martín-Sánchez, Pablo Alonso-González, Alexander Paarmann
Mesoscale and Nanoscale Physics
Spin-orbit coupling driven topological superconductivity in twisted bilayer graphene-WSe$_2$ heterostructures
Kamalesh Bera, Arijit Saha and Tanay Nag
Commencing from the low-energy Bistritzer-MacDonald continuum model of twisted bi-layer
graphene (tBLG) with proximity-induced Ising, Rashba, and intrinsic
spin-orbit couplings (SOCs), we construct the corresponding Bogoliubov-de Gennes
Hamiltonian with conventional $s$-wave pairing and theoretically investigate the emergence of topological superconductivity in it. The latter can possibly be experimentally demonstrated in tBLG, Niobium and tungsten diselenide
heterostructures. The topological superconducting phases, bearing an effective $p$-wave pairing profile and exhibiting inverted band dispersion, are protected by a bulk gap and are topologically characterized by Chern numbers. In the absence of intrinsic SOC, variation of the twist angle and other SOC strengths yield extended gapless, trivial, and topological phases, with phase boundaries exactly matching the closing of direct band gaps. The topological regime exhibits clear band inversion in the combined particle-hole and
spin space, along with distinct Bloch localization profiles compared to the trivial phase. Including intrinsic SOC generates additional topological phases and eliminates the gapless phase, indicating the enhanced stability of the gapped topological superconducting regime in tBLG.
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Statistical Mechanics
Odd transport in a two-temperature Brownian dimer
Iman Abdoli and Hartmut Löwen
We investigate a two-temperature Brownian dimer with odd mobility, characterized by antisymmetric transport coefficients, as a controlled paradigm for odd nonequilibrium dynamics. The system is made of two harmonically confined particles coupled by an elastic spring and connected to reservoirs at different temperatures. Odd mobility converts conservative forces into transverse motion, linking heat exchange to circulating probability currents without requiring external torques, spatial anisotropy, or nonconservative driving. Our exact solution shows that odd mobility creates handed correlations between the two particles while leaving the individual particle distributions isotropic. These correlations arise only when temperature imbalance, elastic coupling, and odd mobility act together, and their handedness reverses when the odd response is reversed. The steady probability current contains two distinct parts: the ordinary irreversible current of a two-temperature dimer and an additional handed contribution generated by odd mobility. When projected onto the motion of each particle, this handed contribution becomes a pair of counter-rotating circulating currents inside the traps. Based on the currents we compute the heat transfer and
entropy production analytically. We show that odd mobility enhances thermal conductance between the reservoirs, while the net heat current and total dissipation remain unchanged under reversal of the odd handedness.
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Quantum Gases · Cross-listed from physics.atom-ph
Quantum statistics on atom-ion Feshbach resonances
Joachim Siemund, Fabian Thielemann, Jonathan Grieshaber et al. (+5 more)
We investigate three-body recombination in a hybrid atom-ion system consisting of a single trapped Ba$^+$ ion immersed in a two-component
Fermi gas of Li atoms near an atom-ion Feshbach resonance. By tuning the
spin composition at constant density and temperature, we isolate the role of
quantum statistics in atom-atom-ion collisions. The measured ion loss rate exhibits a pronounced nonlinear dependence on
spin polarization, revealing a reduced contribution of recombination pathways involving identical
fermions already at the level of experimental observables. The observations are consistent with a two-step recombination picture and an adiabatic hyperspherical approach, where antisymmetrization restricts the available entrance channels and gives rise to interference between indistinguishable recombination pathways. Our work establishes atom-ion systems as a platform for controlling three-body collisions via
quantum statistics and demonstrates that exchange-
symmetry effects remain robust even under thermal averaging that obscures the underlying threshold-law behavior.
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All authors Joachim Siemund, Fabian Thielemann, Jonathan Grieshaber, Wei Wu, Patrick Mullan, Panagiotis Giannakeas, Krzysztof Jachymski, Tobias Schaetz
Mesoscale and Nanoscale Physics
Local and nonlocal STM transport signatures of spin polarization in second order topological superconductors
Paweł Szumniak, Daniel Loss and Jelena Klinovaja
We investigate numerically the
spin and transport properties of two-dimensional second-order topological
superconductors (2D SOTSCs) hosting a pair of Majorana corner states (MCSs). First, we show that MCSs in the considered setup are characterized by a distinct spatial distribution of electronic
spin polarization in the direction perpendicular to an applied in-plane
magnetic field, with opposite signs for each MCS. Such a property can be used to label MCSs in a pair by their electronic
spin. We propose a comprehensive
spin-resolved transport protocol for measuring such a
spin texture and further detecting the braiding (exchange) of a pair of MCSs, a crucial prerequisite for topological
quantum computing. To be specific, we show that the magnitude of local conductance and the sign of nonlocal conductance are precisely linked to the sign of the electronic part of the MCS
spin density and the
spin polarization of the probe. Moreover, we show that the proposed technique can be used to detect the
spin density profile of higher-energy quasiparticle states, e.g., edge states hosted in the SOTSC. We showed that all analyzed features are highly robust to strong static disorder , which makes our findings a clear experimental pathway to verify the
spin structure of MCS and other quasiparticles hosted in SOTSCs.
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Disordered Systems and Neural Networks
Physical Neural Networks Need Nonlinearity, Amplification, and Suppression for Learning
Nex Chiaki Xijana Stuhlmüller and Marjolein Dijkstra
The exponential growth in energy consumption of artificial intelligence systems has spurred interest in physical computing paradigms that exploit the relaxation of physical systems toward steady states. However, many existing physical networks are fundamentally linear and incapable of performing nonlinear operations crucial for meaningful machine learning tasks. Here we use simulations to show that nonlinearity alone is insufficient; physical learning systems must also support signal amplification and suppression to perform nontrivial computations. We present physically plausible
circuit designs that incorporate these essential features, enabling effective nonlinear information processing. Our findings clarify the limitations of linear physical networks and provide guidance for developing energy-efficient physical learning architectures capable of general machine learning tasks.
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Other Condensed Matter
Electric-Field Switchable Magnetic Spin Hall Effect
Mingbo Dou, Xu Chen, Qin Zhang et al. (+4 more)
It is established that the polarity of a time-reversal-odd ($\mathcal{T}$-odd) physical quantity can be reversed under the $\mathcal{T}$ operation. Here, we use the
spin-group analysis to directly demonstrate that the $\mathcal{T}$-odd
magnetic spin Hall effect in ferroelectric altermagnets can be switchable by electric fields beyond the $\mathcal{T}$ operation. This arises from the ferroelectric switching of the nonrelativistic
spin splitting, which swaps the roles of
spin up and down channels in the reciprocal space. As a result, the $\mathcal{T}$-odd
spin conductivity that are proportional to the
spin-polarized conductivity difference reverses its polarity upon polarization switching. We identify
spin-group operations to switch both the polarization and the
magnetic spin Hall effect simultaneously for non-centrosymmetric
spin point groups. Then, we exemplify those phenomena in the ferroelectric altermagnet VOI$_2$ monolayer based on density functional theory calculations and an effective
Hamiltonian analysis. Our findings not only provide novel strategies to switch the
magnetic spin Hall effect using the dissipation-free electric field but also open a promising avenue for electrically programmable spintronic devices.
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All authors Mingbo Dou, Xu Chen, Qin Zhang, Xianjie Wang, Xue-Zeng Lu, Jia Zhang, L. L. Tao
Strongly Correlated Electrons
Coexistence of static order and spin dynamics in an S = 5/2 frustrated triangular antiferromagnet
U. Jena, B. Sana, Satish Kumar et al. (+6 more)
Frustrated triangular-
lattice antiferromagnets in the classical high-
spin limit provide a paradigmatic setting in which the interplay of competing exchange interactions, anisotropy, and collective degrees of freedom can lead to unconventional low-energy excitations, anomalous criticality, and persistent dynamical responses. Here, we present comprehensive thermodynamic, $\mu$SR, and
neutron diffraction experiments, along with first-principles calculations, on a triangular-
lattice antiferromagnet, MnSnB$_2$O$_6$, where Mn$^{2+}$ ($S=5/2$) moments form a nearly perfect 2D triangular network without any anti-site disorder. The Curie-Weiss fit to the
magnetic susceptibility yields a moderate Curie-Weiss temperature of $-12$ K, indicating dominant
antiferromagnetic interactions between Mn$^{2+}$ moments, which is supported by first-principles calculations. Specific-heat measurements reveal the onset of long-range
magnetic order at $T_{\rm N}\approx 1$ K, which is ascribed to intraplane exchange interactions. The specific heat exhibits pronounced short-range correlations above $T_{\rm N}$ and an unconventional power-law behavior, $C\propto T^{1.37}$, deep in the ordered state, suggesting the presence of non-trivial low-energy excitations. Zero-field $\mu$SR experiments down to 50~mK confirm the presence of
magnetic ordering below $T_{\rm N}$, in agreement with thermodynamic and
neutron diffraction experiments. The $\mu$SR measurements detect persistent
spin dynamics coexisting with static
magnetic order. The temperature
evolution of the order parameter down to 50~mK from
neutron diffraction suggests that the ordered state is consistent with a 3D Ising-like antiferromagnet. This family of archetypal frustrated magnets offers a promising venue for the experimental realization of emergent phenomena governed by competing exchange interactions and exotic low-energy excitations.
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All authors U. Jena, B. Sana, Satish Kumar, M. Pregelj, A. Bandyopadhyay, P. Manuel, J. S. Lord, D. T. Adroja, P. Khuntia
Superconductivity
Quasiclassical theory of nonlinear response in d-wave superconductors
Aidan Steineman, Samuel Awelewa and Maxim Dzero
We use a self-consistent Keldysh–Nambu quasiclassical theory to study two related nonlinear phenomena in clean d-wave
superconductors: the photo-induced static correction to the order parameter – the Eliashberg effect – and third-harmonic generation. Both follow from a systematic perturbative solution of the out-of-
equilibrium Eilenberger equation for the Keldysh propagator. For the steady-state correction to the pairing amplitude we find that at temperatures close to the critical temperature and to leading order in the gap magnitude $\Delta$, the photo-induced change of the order parameter is zero at all drive frequencies: in contrast to s-wave
superconductors, a clean d-wave
superconductor exhibits no Eliashberg enhancement at this order. The gap-enhancing quasiparticle-redistribution channel that drives the effect in the s-wave case is suppressed by an additional power of $\Delta$ in the d-wave case. For third-harmonic generation we find that the charge-density-fluctuation (particle–hole) channel significantly dominates the Schmid–
Higgs amplitude-mode contribution over a broad frequency range, the two becoming comparable only in a narrow window near the resonance frequency $\omega\approx 2\sqrt{2}\,\Delta$ if one neglects the diamagnetic part of the current in the normal state. We trace this to the nonequilibrium dynamics of nodal quasiparticles, which must be retained explicitly and which also makes the response sensitive to the orientation of the driving field.
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Mesoscale and Nanoscale Physics
Rashba Spin Demons in Two-Dimensional d-Wave Altermagnets and their Electrostatic Contro
Muhammad Irfan Sarwar, Mohsin Raza and Kashif Sabeeh
Spin demons in d-wave altermagnets are acoustic collective excitations produced by nearly out-ofphase motion of
spin-split quasiparticle populations. We identify a new mode, Rashba
spin demon mode, in 2D d-wave altermagnets in the presence of Rashba
Spin-Orbit Coupling (RSOC). The pristine
spin demon mode in altermagnets, without RSOC, is a charge-dark excitation which is invisible to charge-sensitive probes. We show that Rashba
spin demon mode is a
spin-dominated acoustic mode that is distinct from the pristine mode and has a finite charge density spectral weight. RSOC rotates the quasiparticle
spin texture in momentum space, generating mixed charge-
spin coherence factors that give the longitudinal
spin pole a charge residue. We also show that a nearby metallic gate provides a complementary electrostatic knob by screening the Coulomb interaction and tuning the pole dispersion and linewidth. Within a charge-
spin random-phase approximation, we identify regimes where the Rashba mode is underdamped, charge visible, and still predominantly longitudinal-
spin-like. Our results establish RSOC and electrostatic screening as complementary controls for tuning the
spin and charge character of altermagnetic
spin demons and making them accessible to charge probes without destroying their
spin-dominated character.
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Statistical Mechanics · Cross-listed from quant-ph
Dissipation-Induced Deviations from Kibble-Zurek Scaling in Non-Hermitian Quantum Annealing
H. Najafzadeh, S. Sadeghizade, R. Jafari et al. (+1 more)
We revisit the
quantum annealing problem in the non-Hermitian transverse-field Ising model. We determine, both analytically and numerically, the intrinsic transition probabilities and the resulting defect density. Our results reveal that, unlike the Hermitian case where defect production is dominated by modes near the gap-closing point, the non-Hermitian dynamics involve significant contributions from broad momentum sectors. We find that, depending on the dissipation strength, the defect density exhibits standard Kibble-Zurek scaling, anti-Kibble-Zurek behavior, and a suppression faster than the Kibble-Zurek prediction. We demonstrate that these deviations from the standard Kibble-Zurek scaling can be understood in terms of the underlying excitation probabilities. Specifically, the fast decay of the defect density originates from a vanishing excitation probability spanning a range of annealing times across all allowed modes, even at the gap-closing points. In contrast, the anti-Kibble-Zurek behavior arises from supplementary excitations facilitated by dissipation over a broad range of allowed modes, particularly those situated away from the gap-closing region.
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All authors H. Najafzadeh, S. Sadeghizade, R. Jafari, A. Langari
Materials Science
HF Etching and Silanization: Evidence for the Role of Surface Hydroxyl Groups in Silicon Nitride Resonator Loss
Ariane Giesriegl, Nicola Cavalleri, Robert West et al. (+4 more)
Silicon nitride $SiN_x$ nanomechanical resonators are central to sensing,
quantum technologies, and fundamental physics experiments due to their exceptional mechanical quality factors (Q). However, as resonator thickness approaches the nano-scale, surface-related dissipation limits performance. Here, we investigate the role of surface chemistry in low-stress Si-rich SiNx membranes through a combination of hydrofluoric acid (HF) etching and trimethylchlorosilane (TMCS) silanization, correlated with surface characterization and mechanical measurements. Preliminary analysis by TEM-EELS, XPS, RBS/ERDA, and XRR reveals a native
oxide surface layer (1-2 nm). Surface modification by HF and TMCS was subsequently evaluated using XPS, photothermal FTIR, contact-angle measurements, and intrinsic quality factor ($Q_{int}$) characterization. While HF etching effectively removes the native
oxide and TMCS introduces hydrophobic $Si-(CH_3)_3$ termination, neither
oxide thickness nor surface energy correlates with mechanical dissipation. TMCS treatments produce the largest enhancements, increasing $Q_{int}$ by up to 50%, whereas HF etching alone yields lower gains of 20-25%. These findings suggest surface hydroxyl groups as a key contributor to energy loss in $SiN_x$ resonators and demonstrate that chemical functionalization can substantially suppress surface dissipation.
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All authors Ariane Giesriegl, Nicola Cavalleri, Robert West, Antonius Armanious, Markus Sauer, Thomas Schachinger, Silvan Schmid