Statistical Mechanics · Cross-listed from quant-ph
Non-Markovian Quantum Decay in Complex Environments: A Hyperstatistical Approach
Nicola Fabiano
The exponential decay of an unstable
quantum state, as described by standard Markovian theories such as Fermi's Golden Rule, assumes a simple, structureless environment. However, in complex environments characterized by disorder, long-range interactions, or strong fluctuations, local decay rates fluctuate, leading to non-Markovian dynamics and power-law “long-time tails.” In this paper, we apply the recently proposed hyperstatistics framework to the problem of
quantum decay in such complex environments. By considering a $\gamma$-distribution of local decay rates across mesoscopic domains, we derive a macroscopic survival probability governed by a $q$-exponential function. We then use the $q$-generalized Gamma function, defined via the Mellin transform of the $q$-exponential, to calculate the moments of the decay-time distribution. We show that the mean
quantum lifetime is $\langle t\rangle = \int_0^\infty P(t)\,dt= [\langle\Gamma\rangle(2-q)]^{-1},$ and is therefore finite for $q<2$. The convergence of the second moment, and hence of the lifetime variance, instead requires the stricter condition $q<3/2$. These results provide a refined physical interpretation: for $1<q<3/2$ both the mean lifetime and its variance are finite; for $3/2\le q<2$ the mean lifetime remains finite but lifetime fluctuations become infinitely broad; and for $q\ge2$ the mean lifetime itself diverges, corresponding to a truly trapped, localized, or Griffiths-like regime.
Read the full abstract ▾
Materials Science
Vibrational Origin of the Barocaloric Effect in the Spin-Crossover Complex Fe(pap-5NO2)2: A Combined DFT and Mean-Field Study
Alan de Souza, Antonio M. dos Santos, Yongqiang Cheng et al. (+2 more)
Despite the barocaloric performance recently reported for the
spin-crossover complex Fe(pap-5NO2)2, the microscopic origin of its pressure-induced
entropy change remains poorly understood. In particular, the relative contributions of vibrational, configurational, and
spin degrees of freedom to the barocaloric response have not yet been quantitatively established. Here, we develop a theoretical framework that combines density functional theory (DFT) calculations with an effective mean field
Hamiltonian to investigate the barocaloric effect in this
spin-crossover complex. Vibrational frequencies of the low-
spin (S = 0) and high-
spin (S = 2) states obtained from first-principles calculations are incorporated into a thermodynamic model that explicitly accounts for configurational,
spin, and
lattice entropy contributions. By establishing a correspondence between the vibrational spectra of both
spin states through displacement-vector overlap analysis, we identify low and mid frequency metal-ligand vibrations as the primary microscopic origin of the vibrational
entropy change. The proposed model quantitatively reproduces the experimentally reported barocaloric
entropy change for a pressure variation of 2 kbar, corresponding to a maximum reversible
entropy change of approximately 70 J kg-1 K-1, and predicts a
spin-crossover temperature of T_1/2 = 313 K under ambient pressure, in excellent agreement with the experimental value of 308 K. Analysis of the
entropy components reveals that
lattice entropy associated with molecular vibrations accounts for approximately 84% of the total barocaloric response, whereas configurational and
spin contributions are comparatively small.
Read the full abstract ▾
All authors Alan de Souza, Antonio M. dos Santos, Yongqiang Cheng, Vinícius S. R. de Sousa, Mario Reis
Superconductivity · Cross-listed from quant-ph
Parametric amplification in a Kerr Oscillator based on Ne FIB Nanobridges
Parth Bhandari, Laith Meti, Gemma Chapman et al. (+3 more)
Superconducting
circuits play a crucial role in the advancement of
quantum computing and
quantum sensing. Typically such
circuits require the presence of a non-linear element, where the engineered anharmonicity (Kerr factor) and resonant linewidth determine the potential applications of the
circuit. In this work we have fabricated Nb-based CPW resonators embedded with a DC SQUID incorporating Nb nanobridges as the weak links. We use two-tone spectroscopy to study the non-linear behaviour of the device at 15 mK up to a field of 2.48 mT. Under the application of a blue-detuned pump, the device shows a decrease in the resonant frequency which is used to estimate the Kerr factor. We further apply a red-detuned pump to go beyond the bifurcation threshold and observe the appearance of an additional idler mode with net gain. The gain of the device was maximized by further decreasing the pump frequency, showing a maximum amplification of 15 dB. Finally, we show agreement between the Kerr non-linear oscillator model and the measured transmission spectrum, and highlight further design modifications to improve the gain and bandwidth of such devices.
Read the full abstract ▾
All authors Parth Bhandari, Laith Meti, Gemma Chapman, Edward Romans, John Gallop, Ling Hao
Statistical Mechanics · Cross-listed from quant-ph
Quantum optomechanics with arbitrary mirror displacement: nonlinear Langevin equation with non-Markovian back-action noises
Adrian E. Rubio Lopez, Hing-Tong Cho and Bei-Lok Hu
Quantum optomechanics (QOM) explores the interaction between a
quantum field, often confined in a cavity, and the
quantum motion of mirrors, membranes or material media, usually assumed slow enough with negligible particle production, which is the central concern of dynamical Casimir effects, and a drive
laser field for effective control. This rapidly developing field has a wide range of applications, from
quantum sensing to the detection of gravitational waves. Because the opto-mechanical coupling is nonlinear, most theoretical investigations assume that the amplitude of mirror motion $x$ remains small. Recent years saw several papers treating $x^2, x^3$ orders in the mirror displacement. In our work we take a different route, deploying the functional perturbative method presented in [1] and enriched in [2], applicable for sufficiently weak opto-mechanical couplings. With this we can treat arbitrary displacement of the mirror, not just at a higher order in a power series expansion in $x$. We first derive the influence action of the
quantum field and its non-Markovian noises back-reacting on the moving mirror with self-consistency. From it we derive a nonlinear Langevin equation driven by these back-action noises from the
quantum field. We then show how results from our general modeling and treatment can be linked with the models and the Langevin equations presented in the literature, starting with the popular radiation pressure $Nx$ coupling, with $N$ the
photon number, up to the recent $x^3$ order results. We hope this new approach and the results presented here can provide useful theoretical support for high precision QOM experimentation in the future.
Read the full abstract ▾
Disordered Systems and Neural Networks · Cross-listed from math.PR
Algorithmic threshold for high-dimensional projection pursuit I: general theory
Brice Huang, Mark Sellke and Nike Sun
We study a null model of high-dimensional projection pursuit: we are given $M$ points sampled i.i.d. from a standard gaussian in $N$ dimensions, where $M,N\to\infty$ with $M/N\to\alpha\in(0,\infty)$. Our goal is to characterize the possible empirical distributions of these points' projections along a data-dependent direction $x$, which ranges over either the sphere $S_N=\sqrt{N}\mathbb{S}^{N-1}$ or cube $\Sigma_N=\{-1,+1\}^N$. We consider this problem in an algorithmic setting, where $x$ must be the output of an
algorithm with dimension-free Lipschitz dependence on the input; this class of
algorithms includes general gradient-based methods such as Langevin dynamics and approximate message passing (AMP). Our main result exactly characterizes the set of empirical distributions attainable by this class in terms of a one-dimensional
stochastic control problem. As a consequence of our main result, we obtain exact algorithmic thresholds for optimizing the
Hamiltonian of a spherical or Ising perceptron model with general bounded continuous activation. For the spherical problem, independent work of Montanari and Zhou (2024) characterized the empirical distributions attainable by a related two-stage AMP
algorithm, also in terms of
stochastic control. Our proof of hardness builds on the branching overlap gap property introduced in earlier work by the first two authors. Our main innovation is to develop
stochastic control theory within the branching OGP framework, significantly expanding the settings in which it locates an exact algorithmic threshold. Notably, our methods apply even though the non-algorithmic problem of characterizing all feasible projections remains a major outstanding challenge. For the matching algorithmic result, we construct a new incremental AMP
algorithm that acts on a Brownian-bridge revelation of the gaussian disorder and simulates the same family of controlled SDEs.
Read the full abstract ▾
Materials Science
PINN-Phase: A physics-informed neural network for curvature-driven multiphase-field evolution
Seifallah Elfetni, Sascha Thinius, Peter H. Seeberger et al. (+1 more)
Phase-field simulation of polycrystalline microstructures becomes costly when many related cases must be evolved over long times. We introduce PINN-Phase, a physics-informed neural time integrator that advances the full multiphase field from its initial condition and enforces phase bounds and unit sum at every step. On the reported explicit multiphase-field path, it learns from the governing residual on its own predicted states, without post-initial-condition reference states in the loss or checkpoint selection. A fixed 25-grain model satisfies the complete predefined criteria in seven of eight prospectively fixed unseen microstructures and in both deliberately atypical stress cases, with 0.94-3.71% terminal label disagreement. At native 128^3 resolution, an eight-grain model trained on four initial microstructures retains 98.79% label agreement and exact survivor identities on a training case after 24,000 autonomous steps, 5.86 times its represented training horizon. On six prospectively fixed unseen 128^3 initial conditions, label disagreement at the last saved state within that horizon is 0.72-2.11%; after autonomous
evolution to 24,000 steps, or 5.86 times the represented training horizon, five of six retain the exact terminal survivor set. At 64 grains, terminal disagreement decreases from 6.09% in the primary evaluation to 3.97% after continued training, with exact recovery of the 21-grain survivor set. These results demonstrate structurally admissible long-horizon neural integration and direct initial-condition transfer within fixed
benchmark families.
Read the full abstract ▾
All authors Seifallah Elfetni, Sascha Thinius, Peter H. Seeberger, Theodore Tyrikos-Ergas
Superconductivity
Controlling Intertwined Electronic Orders in FeSe with Exfoliation
Wenyao Liu, Gabriel Natale, Kyung-Mo Kim et al. (+14 more)
Controlling intertwined electronic orders in two-dimensional
superconductors offers an effective route to answering fundamental questions and engineering new
quantum devices. However, tuning the balance between competing orders typically requires complex chemistry, strain, or interface engineering. Here, we show that a pristine alternative is the dimensional reduction of the unconventional
superconductor FeSe. Exfoliation suppresses the bulk electronic nematic response and switches the superconducting
symmetry from bulk s-wave to d-wave-dominant. Transport, electron microscopy, and Raman spectroscopy establish the substantial weakening of nematic order in thin flakes. To probe superconductivity, we perform angle-dependent Andreev reflection spectroscopy on pristine
crystal edges. As the junction's orientation is rotated, the spectra evolve from zero-energy bound states to coherence peaks. The injection angle, field, and temperature dependence, along with theoretical modeling, confirm that exfoliation switches the superconducting
symmetry. Our results suggest a versatile superconducting platform for engineering
quantum orders and provide fresh insights into the underlying pairing mechanisms.
Read the full abstract ▾
All authors Wenyao Liu, Gabriel Natale, Kyung-Mo Kim, Birender Singh, Piyush Sakrikar, Stephen D. Funni, Leo Kondo, Augustin Davignon, Antoine de Lagrave, Kota Ishihara, Michael Geiwitz, Maia G. Vergniory, Takasada Shibauchi, Jun Sung Kim, Michał Papaj, Judy J. Cha, Kenneth S. Burch{\dag}
Other Condensed Matter
Dynamical backaction in nanoscale superfluid electromechanics
Marek Talíř, Filip Novotný, Balázs Szalai et al. (+2 more)
Nanofluidic acoustic resonators employing superfluid $^4$He can be used to study quantized
vortices from collective behavior in two-dimensional superfluid
turbulence down to few individual
vortices created by rotation. In order to improve sensitivity to the level needed for probing individual quantized
vortices, readout mechanisms employing optomechanical or optomechanics-inspired approaches seem to be promising in this regard. In this work, we develop an electromechanical system, which couples a 4$^\mathrm{th}$ sound acoustic resonance to a superconducting LC tank
circuit in a sideband-resolved regime. Using this system, we demonstrate electromechanically induced transparency (EMIT), optical spring effect and optomechanical sideband damping and amplification. Furthermore, by rotating the cryostat, we demonstrate sensitivity to quantized
vortices, which can become trapped and released in avalanche-like process inside the nanofluidic volume.
Read the full abstract ▾
All authors Marek Talíř, Filip Novotný, Balázs Szalai, Nasiruddin Mondal, Emil Varga
Materials Science
Elastic properties of amorphous LiTaCl$_6$ solid-state electrolyte
Xiaolin Liu and De-en Jiang
Amorphous solid-state electrolytes are attractive candidates for safe, high-energy-density all-solid-state batteries, yet their mechanical properties remain poorly understood from a computational perspective. Here, we investigate the elastic behavior of the recently discovered amorphous superionic Li-ion conductor LiTaCl$_6$ using density-functional-theory (DFT)-based methods, including unrelaxed static, relaxed static, and strain fluctuations from molecular dynamics (MD) simulations in the isobaric–isothermal (NPT) ensemble with DFT-trained machine-learning force fields (MLFFs). While the unrelaxed static method predicts a Young's modulus an order of magnitude higher than the experiment, the relaxed static method—commonly applied to crystalline electrolytes—still overestimates the modulus by more than 170%. In contrast, the MD approach using MLFFs yields a Young's modulus of $2.84 \pm 0.26$ GPa, which quantitatively agrees with the experimental value of $2.91 \pm 0.32$ GPa. Using the MLFF-MD approach, we further predict bulk modulus (4.44 GPa), shear modulus (1.02 GPa), and Poisson's ratio (0.39) for amorphous LiTaCl$_6$ and conclude that elastically it behaves like a soft
polymer or gel. These results demonstrate that amorphous superionic materials possess some unique elastic properties and that, among the methods examined, only the MLFF-MD approach yields quantitative agreement with experiment, highlighting the necessity of a dynamical treatment to simulate their elastic response, consistent with recent findings for crystalline superionic conductors.
Read the full abstract ▾
Statistical Mechanics · Cross-listed from quant-ph
Quantum work extraction from partial information and with finite resources
Giacomo Guarnieri, Diego Maragnano, Giulia Gamba et al. (+2 more)
Information can be converted into work, but in
quantum mechanics information about a state is not freely available: it must be inferred statistically from measurements on a finite number of copies. We study work extraction in this finite-resource setting by introducing a partial-information and finite-resources (PIFR)
quantum Maxwell's demon. Given $N$ identical copies of a state with known
Hamiltonian, the demon measures $M$ copies to estimate the state and the corresponding ergotropic
unitary, which is then applied to the remaining $N-M$ copies. This protocol induces a trade-off between information acquisition, reconstruction accuracy, and thermodynamic yield, making the total extracted work normalized to the ideal ergotropic
benchmark the relevant figure of merit. As our central result, we derive a universal closed-form trade-off bound that places this ergotropic efficiency between a Carnot-type ceiling $1-M/N$ and a floor controlled by a reconstruction precision rooted in finite-sample
quantum estimation theory; optimizing the copy allocation yields $M^*\propto N^{2/3}$ and an $N^{-1/3}$ approach to the ideal limit, set by a conservative, worst-case reconstruction precision. By considering standard
quantum state
tomography, we numerically verify the presence of an optimal resource distribution, which also depends on the purity of the state under consideration. Our results identify finite-copy work extraction as a genuinely task-dependent inference problem, in which estimation strategies should be judged by thermodynamic performance rather than reconstruction fidelity alone.
Read the full abstract ▾
All authors Giacomo Guarnieri, Diego Maragnano, Giulia Gamba, Lorenzo Zoppelletto, Marco Liscidini
Statistical Mechanics · Cross-listed from quant-ph
Convex conservation of von Neumann entropy implies unitarity or antiunitarity
Nicolas G. Underwood and Jonte R. Hance
On the space of density
matrices $D(H)$, Kadison's
theorem establishes that all invertible convex transformations $K:D(H)\to D(H)$ are unitarity or antiunitary. For a finite
Hilbert space, we propose a similar
theorem which replaces the invertibility requirement with that of
entropy conservation. Thus, we argue, the supposition of reversibility in
quantum mechanics may be replaced with a principle of
entropy conservation.
Read the full abstract ▾
Soft Condensed Matter
"Ultra-weak" First-Order Phase Transition in Biaxial Liquid Crystals
Soumyajit Pramanick, Mrinal Kanti Debnath, Nababrata Ghoshal et al. (+2 more)
We report high-resolution Monte Carlo evidence characterizing the hierarchy of transition strengths in biaxial nematogens. By employing multiple histogram reweighting on large
lattices, we demonstrate that while the isotropic-to-uniaxial ($I \to N_U$) transition is
symmetry-enforced first-order, the uniaxial-to-biaxial ($N_U \to N_B$) transition in the region between the tricritical point and the triple point ($\lambda = 0.26$) is proximity-driven and more than an order of magnitude smaller for large system sizes. Such a class of ultra-weak first-order transitions could be a new pathway for future investigations.
Read the full abstract ▾
All authors Soumyajit Pramanick, Mrinal Kanti Debnath, Nababrata Ghoshal, Soumen Kumar Roy, Sudeshna Dasgupta
Materials Science
Strain-Driven Electronic and Catalytic Modulation of g-C3N4/GeS van der Waals heterostructure for Photocatalytic Water Splitting
Soumendra Kumar Das, Smruti Ranjan Parida, Tapas Kumbhakar et al. (+2 more)
Photocatalytic water splitting offers a viable pathway for sustainable hydrogen production. In this study, first-principles density functional theory calculations were performed to explore the strain-dependent photocatalytic behaviour of a two-dimensional g-C3N4/GeS
heterostructure. The
heterostructure shows type-II band
alignment with an indirect band gap of 2.17 eV, smaller than those of the individual g-C3N4 (2.81 eV) and GeS (3.31 eV) monolayers. Biaxial tensile strain up to 3% effectively modulates the band gap and band edge positions, allowing suitable
alignment with water redox potentials. The calculated Gibbs free energy for the hydrogen
evolution reaction ({\Delta}GHER) is 0.2 eV for the pristine
heterostructure and approaches near-thermoneutral values (-/+ 0.1 eV) under +1% and +2% strain. Meanwhile, the OER overpotential decreases from 2.17 V to 0.97 V with increasing strain. AIMD simulations and optical absorption in the visible region confirm the thermodynamic stability and promising photocatalytic potential of the
heterostructure for hydrogen generation.
Read the full abstract ▾
All authors Soumendra Kumar Das, Smruti Ranjan Parida, Tapas Kumbhakar, Prasanjit Samal, Sridhar Sahu
Materials Science
Analogue Phase Change Computational Memory with High Precision Reads and Energy Efficient Writes
Ghazi Sarwat Syed, Loris Coccia, Vara Prasad Jonnalagadda et al. (+4 more)
Resistive
memory technologies offer a compelling advantage for in-
memory computing. However, realizing a device architecture that simultaneously achieves high computational precision, efficiency, and density has remained elusive due to inherent trade-offs among these performance metrics. Here, we introduce a com- pact phase-change
memory device architecture that combines an ultra-confined active switching volume for enhanced electro-thermal efficiency with a non-insulating thin film that suppresses temporal conductance fluctuations. We analytically model and back-end integrate these devices into crossbar arrays. Even with conventional, undoped phase-change materials, the device architecture enables a computational precision approaching 6 bits, low conductance values below 50 {\mu}S with an adequate conductance window, and a viable pathway toward sub-100 {\mu}A programming currents under nominal operating voltages.
Read the full abstract ▾
All authors Ghazi Sarwat Syed, Loris Coccia, Vara Prasad Jonnalagadda, Antonio Massimiliano Mio, Asit Ray, Matthew BrightSky, Abu Sebastian
Strongly Correlated Electrons
Collinear and noncollinear antiferromagnetic ordering in a highly frustrated decorated square kagomé lattice antiferromagnets of the nabokoite family
V.N. Glazkov, Ya V. Rebrov, M.A. Dubovitskii et al. (+5 more)
Nabokoite family compounds ACu$_7$(TeO$_4$)(SO4)$_5$X (A=Na, K, Rb, Cs; X=Cl, Br) host frustrated 2D square kagom'{e}
lattice layers decorated by additional inter-layer
magnetic ions. We study
magnetic order in nabokoites with multi-frequency electron
spin resonance spectroscopy and thermodynamic measurement (specific heat, magnetization and dielectric permittivity). Our study reveals that the choice of the low-temperature ground state is qualitatively different in light-alkali-ion (K, Na) and heavy-alkali-ion (Rb, Cs) compounds. Heavy-alkali-ion nabokoites order in conventional collinear antiferromagnetic pattern with easy-axis anisotropy. The parameters of the ordered antiferromagnetic state are very close for all heavy-alkali-ion subfamily. Light-alkali-ion members of nabokoite family demonstrate much more complicated route to the ordered state: firstly, a ferroelectric transition at 25-90K lifts the frustration and thus pre-cooks the low-temperature ordering; secondly, an unusual noncollinear
magnetic order develops via two-step phase transition with first transition temperature $T_{c1}\simeq 5-6$K and the second transition at $T_{c2}\simeq 3-4$K. Noncollinear order is evidenced by observation of characteristic non-Larmor antiferromagnetic resonance mode.
Spin dynamics of light-alkali-ion nabokoites is characterized by three zero-field
magnon gaps and two
spin-reorientation fields, the values of
magnon gaps and critical fields are quite different for different compounds. The finite-size cluster modeling of pyramidal structural block of nabokoite structure combined suggests that the critical closeness of the nabokoite exchange coupling parameters to the border-line between the different
quantum ground state of pyramidal building block of nabokoite structure could be the clue to the choice of qualitatively different ordered state in light- and heavy-alkali-ion nabokoites.
Read the full abstract ▾
All authors V.N. Glazkov, Ya V. Rebrov, M.A. Dubovitskii, M.M. Markina, K.V. Zakharov, A.F. Murtazoev, P.S. Berdonosov, A.N. Vasiliev
Mesoscale and Nanoscale Physics
Heavy-Hole–Light-Hole Mixing and Spin–Photon Coupling in Germanium Flopping-Mode Qubits
Jose Reina-Gálvez and Guido Burkard
Intrinsic
spin–orbit interaction in germanium provides electrically active flopping-mode
qubits without requiring
magnetic-field gradients to generate
spin–charge hybridization. We study double
quantum dots (DQDs) with a multiband Luttinger–Kohn framework that retains heavy-hole (HH) and light-hole (LH) states on equal footing. Modeling vertical confinement with a finite confinement potential along the growth direction brings selected subbands into a regime of appreciable HH–LH mixing. This admixture activates electric-dipole
spin-coupling through LH–LH and LH–HH transitions, complementing the conventional HH–HH pseudospin-flip resonance. For the parameter sets considered, these additional channels can produce larger
spin–
photon figures of merit than the HH–HH transition. HH–LH mixing thus supplies a tunable ingredient for
qubit–cavity coupling in germanium hole-
spin qubits and extends the operating regimes available to
circuit-QED architectures.
Read the full abstract ▾
Strongly Correlated Electrons
Experimental observation of decoupled spin subsystems in decorated square kagomé lattice magnets of the nabokoite family
V.N. Glazkov, Ya V. Rebrov, M.A. Dubovitskii et al. (+4 more)
The square kagomé
lattice (SKL) offers a model platform for investigating
geometric frustration in 2D systems. Nabokoite-family compounds \nabok{A}{X} (A=Na, K, Cs, Rb and X=Cl, Br) extend this physics to a 3D network, where 2D SKL layers are decorated by interlayer
spins. Using electron paramagnetic resonance (EPR), we demonstrate a dramatic splitting of this complex exchange network into two virtually decoupled
spin subsystems: absolute calibration of the electron paramagnetic resonance (EPR) absorption reveals that only a fraction of all copper
spins in nabokoites is EPR-active and this fraction of the
spins orders at the Néel point. Comparison of the EPR absorption and static susceptibility indicates that contribution of the EPR-silent
spin subsystem to total
magnetic susceptibility decreases on cooling. This direct observation of coexisting
magnetic order and possible
spin-
liquid dynamics within a single compound challenges conventional models of unified exchange networks in decorated frustrated
lattices.
Read the full abstract ▾
All authors V.N. Glazkov, Ya V. Rebrov, M.A. Dubovitskii, M.M. Markina, A.F. Murtazoev, P.S. Berdonosov, A.N. Vasiliev
Materials Science
Evaluating LLM-based AI agents integrated with materials synthesis tools: the case of atomic layer deposition
Angel Yanguas-Gil
This work provides an overview of the different strategies that can be used to evaluate the performance of AI models and
agents based on large
language models (LLMs) for materials synthesis. After providing a brief overview of the key technologies behind the current generation of AI
agents based on LLMs, we summarize the different approaches to evaluating these models in the context of materials science and in particular on materials synthesis, with a specific emphasis on scenarios in which the models are directly integrated with experimental tools. We discuss evaluation strategies spanning knowledge and
reasoning benchmarks, tool-use
benchmarks, and closed loop
benchmarks involving the interaction with experimental systems or realistic virtual tools. We use atomic layer deposition (ALD) as a case study, emphasizing how existing approaches in the literature both build from general approaches used beyond materials science and can be generalized to other materials synthesis techniques. Finally, we provide a practical evaluation framework to evaluate LLMs in the context of materials synthesis
Read the full abstract ▾
Materials Science · Cross-listed from quant-ph
Anomalous Frequency Shift in Low-Loss Superconducting Granular Aluminum Resonators
Patrick Winkel, Daniil S. Antonenko, Vishakha Gupta et al. (+5 more)
Superconducting high-kinetic inductance materials like granular aluminum (grAl) are a versatile part of the
circuit quantum electrodynamics (cQED) toolbox, provided their losses at microwave frequencies are low enough. To further advance the use of grAl in
quantum devices, it is indispensable to identify the dominant loss mechanisms. The standard approach pairs electromagnetic simulations of resonator geometry with measured temperature and power dependence of resonance frequency and loss rate. Most materials follow the phenomenological theory of two-level systems (TLSs) at low temperatures, resulting in an initial decrease of the resonance frequency with increasing temperature. In our work, we observe an opposite behavior at the lowest temperatures: The resonance frequency initially increases with both temperature and readout power, contradicting the standard TLS model predictions. We are able to explain a part of the data by an alternative mechanism associated with the effect of superconducting quasiparticles in a granular system with spatially-nonuniform gap. Yet, the observed change in the resonance frequency with temperature is not matched by a proportional change in the loss rate. We also observe anomalous positive frequency responses following high-energy events, characterized by several time scales. While anomalous behavior has been reported previously in grAl, the disagreement with standard models is particularly visible in our devices thanks to their exceptionally low loss rates.
Read the full abstract ▾
All authors Patrick Winkel, Daniil S. Antonenko, Vishakha Gupta, Neel Thakur, Pavel Kurilovich, Luigi Frunzio, Leonid I. Glazman, Robert J. Schoelkopf
Strongly Correlated Electrons
Crystal electric field excitations and an effective-spin-$1/2$ ground doublet in the hyperkagome magnet Yb$_3$Sc$_2$Ga$_3$O$_{12}$
Tingjun Zhang, Zehao Wang, Douglas L. Abernathy et al. (+4 more)
We use inelastic
neutron scattering (INS) to determine the
crystal electric field (CEF) excitations of Yb$^{3+}$ in the rare-earth hyperkagome magnet Yb$_3$Sc$_2$Ga$_3$O$_{12}$. Three nearly dispersionless
magnetic excitations are observed near 58, 68, and 74~meV, corresponding to transitions from the ground-state Kramers doublet to the three excited doublets of the $J=7/2$ multiplet. A Stevens-operator analysis constrained by the local $222$ ($D_2$)
symmetry reproduces the excitation energies and spectral weights and yields an Ising-type ground-state $g$ tensor. The first excited doublet lies approximately 58~meV above the ground state, establishing a well-isolated effective $J_{\mathrm{eff}}=1/2$ degree of freedom over the low-temperature regime relevant to collective magnetism. Notably, the directly measured CEF spectrum substantially revises the level scheme previously inferred from bulk measurements, while preserving the essential low-energy pseudospin description. Two independent fitting protocols give consistent excitation energies, ground-doublet wave functions, and $g$ tensors, despite the nonuniqueness of the individual CEF parameters. The resulting single-ion model also reproduces the characteristic susceptibility, magnetization, and field
evolution of the Schottky anomaly in specific heat. These results establish the microscopic single-ion basis needed to construct an effective exchange
Hamiltonian and to interpret future measurements of low-energy collective excitations in Yb$_3$Sc$_2$Ga$_3$O$_{12}$.
Read the full abstract ▾
All authors Tingjun Zhang, Zehao Wang, Douglas L. Abernathy, Rong-Zhu Lin, Steven J. Gomez Alvarado, Chien-Lung Huang, Pengcheng Dai
Materials Science
Single-pulse strain-induced precessional dynamics of magnetization in Co-doped iron garnet
Héloïse Damas, Carl S. Davies, Tomasz Zalewski et al. (+4 more)
Ultrafast control of magnetization through
lattice excitation provides a route to manipulating
magnetic order on short timescales, yet the role of transient strain in driving magnetization dynamics remains poorly understood. Here, single-shot pump-probe magneto-optical microscopy is used to resolve the structural and
magnetic responses of cobalt-doped yttrium iron garnet to individual 5-ps mid-infrared pulses. The excitation generates a localized strain field together with an outward-propagating elastic wave. Concurrently, the
magnetic contrast decreases following excitation and subsequently reverses on a timescale of approximately 1.5-2 ns before recovering to its initial state. The structural and
magnetic responses exhibit closely correlated wavelength and pulse-energy dependences, indicating a common excitation pathway. Micromagnetic simulations incorporating transient strain reproduce the precessional reorientation of the magnetization within individual domains while largely preserving the labyrinthine domain morphology. These results identify transient
lattice deformation as the link between single-pulse mid-infrared excitation and reversible precessional magnetization dynamics in Co-doped yttrium iron garnet.
Read the full abstract ▾
All authors Héloïse Damas, Carl S. Davies, Tomasz Zalewski, Petr M. Vetoshko, Vladimir I. Belotelov, Andrzej Stupakiewicz, Andrei Kirilyuk
Statistical Mechanics
Ornstein-Uhlenbeck Process Driven by Multiple Dichotomous Noises
Silvio Kalaj, Dongho Lee, Enzo Marinari et al. (+3 more)
We study a generalized Ornstein-Uhlenbeck process driven by a superposition of $K$ independent dichotomous noises with arbitrary fixed amplitudes and switching rates. Unlike the classical Ornstein-Uhlenbeck process driven by
equilibrium Gaussian white noise, the present system is governed by bounded nonequilibrium fluctuations with finite correlation times. We obtain exact expressions for the stationary position distribution and all cumulants, and show that the stationary state possesses an unexpectedly rich structure, including compact support, algebraic branch-point singularities, edge divergences, and multiple extrema. We establish a mapping onto a heterogeneous random-flight process with bounded jumps, yielding a transparent probabilistic interpretation of the stationary measure. We further analyze several limiting regimes, including the crossover to Gaussian statistics for large numbers of noise sources. For ensembles with exponentially-distributed quenched amplitudes, we derive exact disorder-averaged stationary distributions and show that disorder fundamentally alters the stationary state, producing exponential tails decorated by algebraic prefactors with non-trivial exponents.
Read the full abstract ▾
All authors Silvio Kalaj, Dongho Lee, Enzo Marinari, Jae-Hyung Jeon, Pascal Viot, Gleb Oshanin
Mesoscale and Nanoscale Physics · Cross-listed from quant-ph
Probabilistic generation of two-mode binomial cat states using cross-Kerr interactions
S. Zhao, A. Metelmann and S. Qvarfort
Superpositions of macroscopically distinct coherent states, or cat states, are a key resource for
quantum technologies. In particular, two-mode binomial cat states can give rise to exact
quantum error correction in continuous-variable
quantum computing. However, their preparation typically requires non-Gaussian initial states, such as Fock or NOON states, which are challenging to realize experimentally. Here, we propose a protocol to generate two-mode binomial cat states where the only requirements are Gaussian initial states in combination with heralded heterodyne measurements. Our approach utilizes cross-Kerr interactions between bosonic modes commonly realizable in superconducting
circuit architectures. We show that by adjusting the input state parameters, our protocol remains robust to dissipation under realistic experimental conditions. Our work provides a practical route to realizing multinomial cat states in current experimental platforms without requiring non-Gaussian initial resources, overcoming a key limitation of existing preparation schemes.
Read the full abstract ▾
Mesoscale and Nanoscale Physics
Quantitative Disentanglement of Terahertz Spin and Orbital Pumping in 3d Ferromagnetic Heterostructures
Tongyang Guan, Jiahao Liu, Yuxiao Mo et al. (+3 more)
Spin and orbital pumping - the injection of
spin and orbital angular momentum from a driven ferromagnet into an adjacent nonmagnetic layer - are fundamental processes underlying angular-momentum generation and transport in
magnetic heterostructures. Femtosecond optical excitation extends these phenomena into the ultrafast regime, where spintronic terahertz emission spectroscopy (STES) detects picosecond angular-momentum currents in a contact-free manner through
spin-to-charge and orbital-to-charge conversion. Microscopic theory predicts that orbital-pumping efficiency increases from Fe to Ni across the 3d series, yet whether these predictions hold under ultrafast excitation remains unclear. A central challenge is that
spin and orbital currents are generated simultaneously and contribute additively to the same terahertz emission, preventing their quantitative separation. Here, we overcome this limitation by combining STES with wedge-sample thickness control in
heterostructures whose nonmagnetic layers (Ta, W, and Nb) have
spin Hall and orbital Hall angles of opposite signs. The two angular-momentum channels therefore exhibit distinct emission polarities and thickness dependences, enabling their quantitative decomposition. Systematic measurements on Fe, Co, and Ni
heterostructures reveal that the orbital-pumping contribution increases progressively toward Ni, reaching several tens of percent of the
spin-current contribution - far exceeding theoretical predictions. Even Fe generates a non-negligible orbital current that becomes essential in the thin-nonmagnetic-layer regime. The extracted orbital
diffusion lengths are consistently shorter than
spin diffusion lengths and increase with decreasing
spin-orbit coupling strength of the nonmagnetic layer. These results establish a quantitative framework for ultrafast
spin and orbital pumping in
magnetic heterostructures.
Read the full abstract ▾
All authors Tongyang Guan, Jiahao Liu, Yuxiao Mo, Liangliang Zhu, Yizheng Wu, Zhensheng Tao
Superconductivity
Topological pair density waves in kagome superconductors
Jia-Xin Yin, Xianxin Wu, Mark H. Fischer et al. (+3 more)
The pair density wave (PDW) is an unconventional superconducting state exhibiting periodic pairing modulations due to pairing with finite momentum Q. In two dimensions, multiple Q components of the PDW can have a non-trivial relative phase, breaking time-reversal
symmetry and resulting in a topological electronic structure. Here we review progress on exploring such topological PDWs (TPDWs) and discuss their potential realization in kagome
superconductors. We first introduce the concept of a TPDW starting from the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state and examine the challenges toward its realization. We then discuss the possibility of a TPDW in the kagome
lattice, which intertwines with chiral superconductivity and loop currents, thus connecting to models describing the
quantum anomalous Hall effect. Furthermore, we review the experimental signatures of a TPDW in AV3Sb5 (A = Cs, Rb, K)
superconductors and highlight related
quantum effects, including switchable chiral pairing modulations, Bogoliubov Fermi states, the superconducting diode effect, and the anomalous thermal Hall effect. Finally, we project the future research opportunities of this correlated topological
quantum phase and discuss its broad implications for finite-momentum pairing, topological matter, and chiral superconductivity.
Read the full abstract ▾
All authors Jia-Xin Yin, Xianxin Wu, Mark H. Fischer, Xiao-Yu Yan, Yigui Zhong, Kozo Okazaki
Strongly Correlated Electrons
Evolving charge order in the CDW state of AV$_3$Sb$_5$ metals
Anshu Kataria, Francis Pratt, Peter J. Baker et al. (+7 more)
AV$_3$Sb$_5$ kagome metals are characterized by intertwined electronic and structural orders, which motivated extensive studies in recent years. Yet the details of the electronic state preceding the superconducting phase remain poorly understood. Here we extend our previous investigation [Phys. Rev. Research 7, L032046 (2025)] of RbV$_3$Sb$_5$ using avoided level crossing (ALC)
muon-
spin spectroscopy to the $A$ = Cs and K systems. Consistent with our previous study, we identify a second transition whose origin cannot be attributed solely to an internal
magnetic field, indicating the involvement of an additional electronic mechanism that subtly modifies the charge distribution within the V plane. In particular, the ALC results point towards an additional charge modulation taking place within the charge density wave (CDW) phase and occurring at $T^{*}<T_{CDW}$ for $A$ = Cs and Rb, or in the vicinity of $T_{CDW}$ for $A$ = K.
Read the full abstract ▾
All authors Anshu Kataria, Francis Pratt, Peter J. Baker, Stephen Cottrell, Miki Bonacci, Andrea Capa Salinas, Stephen D. Wilson, Zurab Guguchia, Samuele Sanna, Pietro Bonfà
Materials Science
Directional commensurability stabilizes structural superlubricity in patterned mesoscale interfaces
Viet Hung Ho, Ge Li, Melisa M. Gianetti et al. (+3 more)
Structural superlubricity, arising from
lattice incommensurability, offers a promising route to eliminate friction and associated energy losses in mechanical systems. In real-world systems, roughness and wear currently pose severe limitations on its robustness and especially the contact size. Here, we consider patterned surfaces as a possible route to overcome some of these limitations. We show that the simplest choice of patterning, contacts made up of two incommensurate triangular-triangular patterns, fails at elevated loads because of the small number of load-bearing contacts, causing the maximum local contact pressure to exceed the strength of the superlubric coating. We introduce a square-triangular patterned interface that increases the number of load-bearing contacts and organizes them into continuous contact lines. When sliding along specific directions relative to these lines, superlubricity is maintained at significantly higher loads by reducing pressure-induced coating failure while also remaining somewhat tolerant to surface imperfections. These findings establish a mechanism for stabilizing structural superlubricity against coating failure and a design principle for engineering low-friction interfaces with enhanced load-bearing capacity and defect tolerance.
Read the full abstract ▾
All authors Viet Hung Ho, Ge Li, Melisa M. Gianetti, Bjørn Haugen, Graham L. W. Cross, Astrid S. de Wijn
Soft Condensed Matter
A route to the thermodynamics of colloid-polymer mixtures from structural information
Vikki Anand Varma, Andrew J. Archer and Alberto Scacchi
Liquid-state theory provides a fundamental connection between microscopic structure and macroscopic thermodynamic behaviour. Here, we develop a framework for predicting thermodynamics and phase behaviour directly from structural correlations, using either radial distribution functions or static structure factors as input. The approach constructs a free-energy functional from structural information obtained at a single thermodynamic state point, without requiring explicit knowledge of the underlying interaction potentials. This circumvents a central difficulty in modelling complex fluids, for which effective interactions are often unknown or rely on approximations. We demonstrate the framework for a range of model fluids, including colloidal and colloid–
polymer systems, with predictions in good agreement with molecular simulation data. The results show that structural information at a single state point can provide sufficient information to predict the broader thermodynamic response of a system. This establishes a route toward inferring phase behaviour directly from experimentally measured structure, even when the microscopic interactions are not known a priori.
Read the full abstract ▾
Statistical Mechanics
Light-induced nonconservative static forces in many-body systems
Jinze Li, Xuemei Yang and Zhiyuan Sun
In a
quantum many-body system, a periodic drive can often generate effective static forces on the slow collective degrees of freedom. We study the static forces generated by light on electronic order parameters in solid-state systems. We show that the forces can have nonconservative components that originate from dissipation, i.e., optical absorption. This effect is demonstrated in two nontrivial examples. In excitonic
insulators, via interband excitations, the light field generates a nonconservative force on the phase of the excitonic order parameter. This force leads to an acceleration of the phase, which manifests as a shift of the
photon emission peak from an
exciton condensate. In materials with an incommensurate charge density wave, a propagating light field generates a nonconservative force on the phase of its order parameter. It drives the charge density wave into sliding motion, leading to a DC electric current via topological Thouless pumping.
Read the full abstract ▾
Strongly Correlated Electrons
Electronic phase separation and emergence of a nondimerized insulating phase in VO$_2$ $(110)_{\mathit{R}}$ ultrathin films
S. Inoue, D. Shiga, R. Hayasaka et al. (+3 more)
Using in situ photoemission spectroscopy and x-ray absorption spectroscopy, we investigated the thickness dependence of the electronic structure and V-V dimerization in VO$_2$/TiO$_2$ (110) ultrathin films, in which the one-dimensional V-V chains along the $c_{\mathit{R}}$ axis lie in the film plane. In VO$_2$ $(110)_{\mathit{R}}$ films, the reduction in dimensionality along the surface-normal direction is not expected to impose a
geometric constraint on V-V dimerization, unlike in VO$_2$ $(001)_{\mathit{R}}$ films. Nevertheless, the characteristic spectral changes associated with the temperature-driven metal-
insulator transition observed in thick films persist down to 1.5 nm, whereas at 1 nm an insulating electronic phase is observed without V-V dimerization. This behavior is highly similar to that reported for VO$_2$ $(001)_{\mathit{R}}$, suggesting that the enhancement of Mott instability resulting from reduced dimensionality is a common and essential driving force for the emergence of the nondimerized insulating phase in VO$_2$ ultrathin films. Meanwhile, unlike in VO$_2$ $(001)_{\mathit{R}}$, the nondimerized insulating phase in VO$_2$ $(110)_{\mathit{R}}$ coexists with the phase exhibiting the temperature-driven metal-
insulator transition. Its fraction increases exponentially with decreasing thickness and becomes dominant at 1 nm. The corresponding effective critical thickness is estimated to be 2.2 nm. These results imply that the
geometric orientation of the V-V chains dictates the spatial
evolution of electronic phase separation via strain-mediated phase competition.
Read the full abstract ▾
All authors S. Inoue, D. Shiga, R. Hayasaka, K. Ozawa, A. F. Santander-Syro, H. Kumigashira