Materials Science · Cross-listed from physics.comp-ph
diffpy.morph: Python tools for model independent comparisons between sets of 1D functions
Andrew Yang, Christopher L. Farrow, Pavol Juhás et al. (+22 more)
diffpy$.$morph addresses a need to gain scientific insights from 1D scientific spectra in model independent ways. A powerful approach for this is to take differences between pairs of spectra and look for meaningful changes that might indicate underlying chemical, structural, or other modifications. The challenge is that the difference curve may contain uninteresting differences such as experimental inconsistencies and benign physical changes such as the effects of thermal expansion. diffpy$.$morph allows researchers to apply simple transformations, or "morphs", to one of the
datasets to remove the unwanted differences revealing, when they are present, non-trivial differences. diffpy$.$morph is an open-source Python package available on the Python Package Index and conda-forge. Here, we describe its functionality and apply it to solve a range of experimental challenges on diffraction and PDF data from x-rays and
neutrons, though we note that it may be applied to any 1D function in principle.
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All authors Andrew Yang, Christopher L. Farrow, Pavol Juhás, Luis Kitsu Iglesias, Chia-Hao Liu, Samuel D. Marks, Vivian R. K. Wall, Joshua Safin, Sean M. Drewry, Caden Myers, Dillon F. Hanlon, Nicholas Leonard, Cedomir Petrovic, Ahhyun Jeong, Dmitri V. Talapin, Linda F. Nazar, Haidong Zhou, Samuel W. Teitelbaum, Tim B. van Driel, Soham Banerjee, Emil S. Bozin, Michael F. Toney, Katharine Page, Naomi S. Ginsberg, Simon J. L. Billinge
Materials Science · Cross-listed from physics.comp-ph
DISCOVER: A Physics-Informed, GPU-Accelerated Symbolic Regression Framework
Udaykumar Gajera, Mohsen Sotoudeh, Kanchan Sarkar et al. (+1 more)
Symbolic Regression (SR) enables the discovery of interpretable mathematical relationships from experimental and simulation data. These relationships are often coined descriptors which are defined as a fundamental materials property that is directly correlated to a desired or undesired functional property of the material. Although established approaches such as Sure Independence Screening and Sparsifying Operator (SISSO) have successfully identified low-dimensional descriptors within large feature spaces many existing SR tools integrate poorly with modern Python workflows, offer limited control over the symbolic search space, or struggle with the computational demands of large-scale studies. This paper introduces DISCOVER (Data-Informed Symbolic Combination of Operators for Variable Equation Regression), an open-source symbolic regression package developed to address these challenges through a modular, physics-motivated design. DISCOVER allows users to guide the symbolic search using domain knowledge, constrain the feature space explicitly, and take advantage of optional GPU acceleration to improve computational efficiency in data-intensive workflows, enabling reproducible and scalable SR workflows. The software is intended for applications in computational physics, computational chemistry, and materials science, where interpretability, physical consistency, and execution time are especially important, and it complements general-purpose SR frameworks by emphasizing the discovery of physically meaningful models.
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All authors Udaykumar Gajera, Mohsen Sotoudeh, Kanchan Sarkar, Axel Groß
Strongly Correlated Electrons
D. R. Baykusheva, D. P. Carmichael, C. S. Weber et al. (+12 more)
Quantum control of the many-body wavefunction is a central challenge in
quantum materials research, as it could yield a precise control knob to manipulate emergent phenomena. Floquet engineering, the coherent dressing of
quantum states with periodic non-resonant optical fields, has become an important strategy for
quantum control. Most applications to solid-state systems have targeted weakly interacting or single-ion states, leaving the manipulation of many-body wavefunctions largely unexplored. Here, we use Floquet engineering to achieve
quantum control of a strongly correlated Hubbard
exciton in the one-dimensional Mott
insulator Sr$_2$CuO$_3$. A nonresonant midinfrared optical field coherently dresses the
exciton wavefunction, driving its rotation between bright and dark states. We use resonant third-harmonic generation to quantify ultrafast $\pi/2$ rotations on the Bloch sphere spanned by these
exciton states. Our work advances the quest towards programmable control of correlated states and
exciton-based
quantum sensing.
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All authors D. R. Baykusheva, D. P. Carmichael, C. S. Weber, I-T. Lu, F. Glerean, T. Meng, P. B. M. De Oliveira, C. C. Homes, I. A. Zaliznyak, G. D. Gu, M. P. M. Dean, A. Rubio, D. M. Kennes, M. Claassen, M. Mitrano
Mesoscale and Nanoscale Physics
Strain-Dependent Wetting of Graphene
Darren Wayne Lim, Xavier R. Advincula, William C. Witt et al. (+3 more)
Understanding how water wets
graphene is critical for predicting and controlling its behaviour in nanofluidic, sensing, and energy applications. A key measure of wetting is the contact angle made by a
liquid droplet against the surface, yet experimental measurements for
graphene span a wide range, with no consensus for free-standing
graphene. Here, we use a machine learning potential with ab initio accuracy to provide an atomistic first-principles prediction for this unsolved problem, finding a weakly hydrophilic contact angle of $72.1 \pm 1.5 \deg$. More importantly, we unveil that
graphene's wetting properties are highly sensitive to mechanical strain: tensile strain makes
graphene significantly less hydrophilic, while compressive strain induces coherent ripples around the droplet, resulting in pronounced anisotropic wetting and contact angle hysteresis. We show that there is a strong coupling between the three-phase contact line and the intrinsic thermal ripples of free-standing
graphene, which contributes to this strain sensitivity. Our results demonstrate that the wettability of 2D membranes are governed not only by their chemistry but also by their dynamic morphology, introducing a new class of wetting behaviour unique to atomically thin materials that offers an additional explanation for variability in experimental measurements. These findings reveal that mechanical strain may be a practical route to controlling wetting in 2D nanomaterials-based technologies, with promising consequences for nanofluidic and nano-filtration applications.
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All authors Darren Wayne Lim, Xavier R. Advincula, William C. Witt, Angelos Michaelides, Fabian L. Thiemann, Christoph Schran
Materials Science
Establishing Atomic Coherence in Twisted Oxide Membranes Containing Volatile Elements
Young-Hoon Kim, Reza Ghanbari, Min-Hyoung Jung et al. (+3 more)
Twisted
oxide membranes represent a promising platform for exploring moire physics and emergent
quantum phenomena. However, the presence of amorphous interfacial dead layers in conventional
oxide heterostructures impedes coherent coupling and suppresses moire-induced interactions. While high-temperature thermal treatments can facilitate interfacial bonding, additional care is needed for materials containing volatile elements, where elevated temperatures may cause elemental loss. This study demonstrates the realization of atomically coherent, chemically bonded interface in twisted NaNbO3
heterostructures through controlled oxygen-annealing treatment. Atomic-resolution imaging and spectroscopy reveal ordered perovskite registry accompanied by systematic
lattice contraction and modified electronic structure at the twisted interface, providing signatures of chemical reconstruction rather than physical adhesion. This reconstructed interface mediates highly asymmetric strain propagation in which the bottom membrane remains nearly relaxed while the top membrane accommodates substantial shear strain, thereby establishing a strain gradient that enables long-range electromechanical coupling throughout the twisted
oxide membranes. By resolving the nature of the reconstructed interface, these findings establish a robust pathway for achieving coherent and strain-tunable
oxide moire superlattices, opening pathways to engineer emergent ferroic and electronic functionalities.
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All authors Young-Hoon Kim, Reza Ghanbari, Min-Hyoung Jung, Young-Min Kim, Ruijuan Xu, Miaofang Chi
Materials Science
Kolmogorov-Arnold Networks Applied to Materials Property Prediction
Ryan Jacobs, Lane E. Schultz and Dane Morgan
Kolmogorov-Arnold Networks (KANs) were proposed as an alternative to traditional neural network architectures based on multilayer perceptrons (MLP-NNs). The potential advantages of KANs over MLP-NNs, including significantly enhanced parameter efficiency and increased interpretability, make them a promising new regression model in supervised machine learning problems. We apply KANs to prediction of materials properties, focusing on a diverse set of 33 properties consisting of both experimental and calculated data. We compare the KAN results to random forest, a method that generally gives excellent performance on a wide range of properties predictions with very little optimization. The KANs were worse, on par, or better than random forest about 35%, 60%, and 5% of the time, respectively, and KANs are in practice more difficult to fit than random forest. By tuning the network architecture, we found property fits often resulted in 10-20% lower errors compared to the standard KAN, and typically gave results comparable to random forest. In the specific context of predicting reactor pressure vessel transition temperature shifts, we explored the parameter efficiency and the interpretable power of KANs by comparing predictions of simple KAN models (e.g., < 50 parameters) and closed-form expressions suggested by the KAN fits to previously published deep MLP-NNs and hand-tuned models created using domain expertise of embrittlement physics. We found that simple KAN models and the resulting closed-form expressions produce prediction errors on par with established hand-tuned models with a comparable number of parameters, and required essentially no domain expertise to produce. These findings reinforce the potential applicability of KANs for machine learning in materials science and suggest that KANs should be explored as a regression model for prediction of materials properties.
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Statistical Mechanics
First-Hitting Location Laws as Boundary Observables of Drift-Diffusion Processes
Yen-Chi Lee
First-passage theory usually emphasizes when absorption occurs. Here, we instead treat where absorption occurs (the first-hitting location, or FHL) as a primary boundary observable of drift-
diffusion processes. We formulate its law as the exit measure induced by the
diffusion generator and recover its density from the normal derivative of an
elliptic Green function. This yields exact half-space kernels in arbitrary ambient dimension $d$ for constant drift, with the two- and three-dimensional cases validated by Monte Carlo simulations. In the zero-drift limit, the kernels reduce to scale-free Cauchy-type laws with algebraic tails; drift introduces exponential screening and the characteristic length $\ell_u=\sigma^2/|\mathbf{v}|$, where $\sigma$ is the noise strength and $\mathbf{v}$ is the constant drift vector, thereby localizing the boundary footprint. An
entropy-based effective width provides a finite diagnostic of this crossover. To test the
geometric reach of the planar theory, we also analyze drift-free exterior hitting of a circle. Its exact Poisson kernel recovers the planar Cauchy law as a local near-boundary limit, admits an exact Cauchy-Poisson composition through an intermediate line, and yields a finite-time supporting-line bound. These results organize geometry, drift, and pathwise constraints within a unified description of first-hitting location laws.
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Mesoscale and Nanoscale Physics
Quantum-geometry-enabled Landau-Zener tunneling in singular flat bands
Xuanyu Long and Feng Liu
Flat-band materials have attracted substantial interest for their intriguing
quantum geometric effects. Here we investigate how singular flat bands (SFBs) respond to a static, uniform electric field and whether they can support single-particle dc transport. By constructing a minimal two-band
lattice model, we show that away from the singular band crossing point (BCP), the Wannier-Stark (WS) spectrum of the flat band is well captured by an intraband Berry phase $\Phi_{\mathrm{B}}$. The associated WS eigenstates are exponentially localized along the field direction, precluding dc transport. In contrast, near the BCP the interband Berry connection becomes prominent and drives Landau-Zener tunneling, which bends the flat-band WS ladder and delocalizes the SFB wavefunctions. Remarkably, this regime is governed solely by the maximal
quantum distance $d$ through two
geometric phases $(\theta,\varphi)$: $\theta$ characterizes the tunneling rate and $\varphi$ acts as a generalized Berry phase. These results highlight the essential role of
quantum geometry in enabling nontrivial transport signatures in SFBs.
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Materials Science · Cross-listed from quant-ph
Krypton-sputtered tantalum films for scalable high-performance quantum devices
Maciej W. Olszewski, Lingda Kong, Simon Reinhardt et al. (+9 more)
Superconducting
qubits based on tantalum (Ta) thin films have demonstrated the highest-performing microwave resonators and
qubits. This makes Ta an attractive material for superconducting
quantum computing applications, but, so far, direct deposition has largely relied on high substrate temperatures exceeding \SI{400}{\celsius} to achieve the body-centered cubic phase, BCC (\textalpha-Ta). This leads to compatibility issues for scalable fabrication leveraging standard
semiconductor fabrication lines. Here, we show that changing the sputter gas from argon (Ar) to krypton (Kr) promotes BCC Ta synthesis on silicon (Si) at temperatures as low as \SI{200}{\celsius}, providing a wide process window compatible with back-end-of-the-line fabrication standards. Furthermore, we find these films to have substantially higher electronic conductivity, consistent with clean-limit superconductivity. We validated the microwave performance through coplanar waveguide resonator measurements, finding that films deposited at \SI{250}{\celsius} and \SI{350}{\celsius} exhibit a tight performance distribution at the state of the art. Higher temperature-grown films exhibit higher losses, in correlation with the degree of Ta/Si intermixing revealed by cross-sectional transmission electron microscopy. Finally, with these films, we demonstrate transmon
qubits with a relatively compact, \SI{20}{\micro\meter} capacitor gap, achieving a median quality factor up to 14 million.
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All authors Maciej W. Olszewski, Lingda Kong, Simon Reinhardt, Daniel Tong, Xinyi Du, Gabriele Di Gianluca, Haoran Lu, Saswata Roy, Luojia Zhang, Aleksandra B. Biedron, David A. Muller, Valla Fatemi
Statistical Mechanics
Tuning the strength of emergent correlations in a Brownian gas via batch resetting
Gabriele de Mauro, Satya N. Majumdar and Gregory Schehr
We study a gas of $N$ diffusing particles on the line subject to batch resetting: at rate $r$, a uniformly random subset of $m$ particles is reset to the origin. Despite the absence of interactions, the dynamics generates a nonequilibrium stationary state (NESS) with long-range correlations. Since standard renewal methods fail for $m<N$, we introduce a new general Fokker–Planck framework with an exact recursive closure of marginal densities. We obtain exact results, both for the NESS and for the time dependence of the correlations, which are valid for arbitrary $m$ and $N$. By varying $m$, the system interpolates between an uncorrelated regime ($m=1$) and the fully synchronous resetting case ($m=N$). For all $1<m<N$, correlations exhibit a non-monotonic time dependence due to the emergence of an intrinsic decorrelation mechanism. In the stationary state, the correlation strength can be tuned by varying $m$, and it displays a transition at a critical value $N_c=6$. Our predictions extend to any spatial dimension $d$, where the critical value $N_c=6$ remains unchanged, and they are experimentally testable in existing optical-trap setups.
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Quantum Gases
Superfluidity in the spin-1/2 XY model with power-law interactions
Muhammad Shaeer Moeed, Costanza Pennaforti, Adrian Del Maestro et al. (+1 more)
In trapped-ion
quantum simulators, effective
spin-1/2 XY interactions can be engineered via
laser-induced coupling between internal atomic states and collective
phonon modes. In the simplest one-dimensional ($1d$) traps, these interactions decay as a power-law with distance $1/r^{\alpha}$, with a tunable exponent $\alpha$. For small $\alpha$, the resulting long-range $1d$ XY model exhibits continuous
symmetry breaking, in marked contrast to its nearest neighbor counterpart. In this paper, we examine this model near the phase transition at $\alpha_c$ from the lens of the
spin stiffness, or superfluid density. We develop a
stochastic series expansion (SSE)
quantum Monte Carlo (QMC) simulation and a generalized winding number
estimator to measure the superfluid density in the presence of power-law interactions, which we test against exact diagonalization for small
lattice sizes. Our results show how conventional superfluidity in the $1d$ XY model is enhanced in the long-range interacting regime. This is observed as a diverging superfluid density as $\alpha \rightarrow 0$ in the thermodynamic limit, which we show is consistent with linear
spin-wave theory. Finally, we define a normalized superfluid density
estimator that clearly distinguishes the short, medium, and long-range interacting regimes, providing a novel QMC probe of the critical value $\alpha_c$.
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All authors Muhammad Shaeer Moeed, Costanza Pennaforti, Adrian Del Maestro, Roger G. Melko
Quantum Gases
Correlated dynamics of three-particle bound states induced by emergent impurities in Bose-Hubbard model
Wenduo Zhao, Boning Huang, Yongguan Ke et al. (+1 more)
Bound states, known as particles tied together and moving as a whole, are profound correlated effects induced by particle-particle interactions. While dimer-monomer bound states are manifested as a single particle attached to a dimer bound pair, it is still unclear about
quantum walks and Bloch oscillations of dimer-monomer bound states. Here, we revisit three-particle bound states in the Bose-Hubbard model and find that interaction-induced
impurities adjacent to bound pair and boundaries cause two kinds of bound states: one is dimer-monomer bound state and the other is bound edge state. In
quantum walks, the spread velocity of dimer-monomer bound state is determined by the maximal group velocity of their energy band, which is much smaller than that in the single-particle case. In Bloch oscillations, the period of dimer-monomer bound states is one third of that in the single-particle case. Emergence of bound edge states also requires that interaction-induced defects are greater than the effective tunneling strength of three-particle bound state. Our work provides new insights to basic mechanics and collective dynamics of three-particle bound states.
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All authors Wenduo Zhao, Boning Huang, Yongguan Ke, Chaohong Lee
Soft Condensed Matter
Deep Learning the Small-Angle Scattering of Polydisperse Hard Rods
Lijie Ding and Changwoo Do
We present a deep learning framework for modeling and analyzing the small-angle scattering data of polydisperse hard-rod systems, a widely used models for anisotropic colloidal particles. We use a variational autoencoder-based neural network to learn the mapping from the system parameters such as the volume fraction, rod length, and polydispersity, to the scattering function. The
dataset for training and testing such neural network model is obtained from Markov chain Monte Carlo simulation of 20,000 hard spherocylinders using the hard particle Monte Carlo package from the HOOMD-blue. Four
datasets were generated, each with 5,500 pairs of system parameters and corresponding scattering functions. We use one of the
dataset to investigate the feasibility of the learning, and three additional
datasets with different polydisperse distribution to demonstrate the generality of our approach. The neural network model transcends the fundamental limitations of the Percus-Yevick approximation by accurately capturing anisotropic interactions and high-concentration effects that analytical models often fail to resolve. This framework achieves significantly higher accuracy in reproducing scattering functions and enables a least-square fitting routine for quantitative data analysis.
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Mesoscale and Nanoscale Physics
Scattering-state theory of open Floquet lattices: transfer matrices, branch openness, and robust asymmetry
Ren Zhang, Xiao-Yu Ouyang, Xu-Dong Dai et al. (+1 more)
We establish a scattering-state theory for open one-dimensional Floquet
lattices based on a frequency-domain transfer-
matrix formulation. For real quasienergy, the conjugate-
symplectic structure of the transfer
matrix separates bulk Floquet–Bloch modes into propagating and evanescent sectors, enabling a consistent treatment of interface matching and the shrinking-window smoothing required for long-sample transport. By tracking how incoming states populate deep-bulk propagating branches, we define branch-resolved weights \(p_{\mu\alpha}\) and total branch weights \(p_\mu\). We prove that \(p_\mu\) equals the escape probability of a wave packet initialized on the corresponding branch. In the open geometries considered here, true bound trapping of propagating branches is nongeneric, yielding \(p_\mu=1\) for generic parameters. This generic openness implies that long-sample transport is governed by deep-bulk branch populations rather than by boundary-sensitive interference. Consequently, the integrated left–right transmission asymmetry reduces to the net chirality, and hence the winding contribution, of an isolated Floquet band. The robust topological observable is therefore the accumulated asymmetry plateau, not the detailed transmission line shape, which remains strongly reshaped by nonadiabatic boundaries. A spatially adiabatic boundary serves only as a transparent
benchmark for resolving the branch structure, not as the origin of the topological response.
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All authors Ren Zhang, Xiao-Yu Ouyang, Xu-Dong Dai, Xi Dai
Materials Science · Cross-listed from quant-ph
Optically Addressable Molecular Spins at 2D Surfaces
Xuankai Zhou, Yan-Tung Kong, Cheuk Kit Cheung et al. (+18 more)
Optically addressable
spins at material surfaces have represented a long-standing ambition in
quantum sensing, providing atomic resolution and
quantum-limited sensitivity. However, they are constrained by a finite depth at which the
quantum spins can be stabilized. Here, we demonstrate a hybrid molecular-2D architecture that realizes
quantum spin sensors directly on top of the surface. By anchoring
spin-active molecules onto hexagonal boron nitride (hBN), we eliminate the depth of the
quantum sensor while also exhibiting robust
spin properties from 4~K to room temperature (RT). The Hahn-echo
spin coherence time exceeds \(T_2 = 3.4~\upmu\text{s}\) at 4~K, outperforming values in bulk organic
crystals and overturning the prevailing expectation that
spin inevitably deteriorates upon approaching the surface. By chemically tuning the molecule through deuteration, \(T_2\) improves by more than 10-fold, and under dynamic decoupling, coherence is prolonged to the intrinsic lifetime limit, exceeding 300~\(\upmu\text{s}\). Proximal
proton spins and the
magnetic response of two-dimensional magnets beneath the hBN layer have been detected at RT. These molecular
spins form surface
quantum sensors with long coherence, optical addressability, and interfacial versatility, enabling a scalable, adaptable architecture beyond what conventional solid-state platforms offer.
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All authors Xuankai Zhou, Yan-Tung Kong, Cheuk Kit Cheung, Guodong Bian, Reda Moukaouine, King Cho Wong, Yumeng Sun, Cheng-I Ho, Vladislav Bushmakin, Nils Gross, Chun-Chieh Yen, Tim Priessnitz, Malik Lenger, Sreehari Jayaram, Takashi Taniguchi, Kenji Watanabe, Anton Pershin, Ruoming Peng, Ádám Gali, Jurgen Smet, Jörg Wrachtrup
Quantum Gases
Stability and Decay of Macrovortices in Rotating Bose Gases Beyond Mean Field
Paolo Molignini, M. A. Caracanhas, V. S. Bagnato et al. (+1 more)
We study the formation, stability, and decay of macrovortices in a rotating Bose gas confined by a Mexican-hat potential with a multiconfigurational ansatz. By systematically including correlations beyond the mean-field level, we map the
equilibrium phase diagram and identify regimes of coexistence between
vortex lattices and multiply charge central
vortices. Quench dynamics reveals that macrovortices are robust under changes in rotation or interaction strength, sustaining clean monopole oscillations with well-separated, vorticity-dependent breathing frequencies. In contrast, trap quenches trigger a universal decay process mediated by
vortex-
phonon coupling, in which rotational energy is progressively transferred to compressible modes until the macrovortex splits into singly quantized
vortices. Our results demonstrate that macrovortex lifetimes and decay pathways can be tuned by trap confinement, providing experimentally accessible signatures of
vortex-
phonon interactions and collective energy transfer in correlated
quantum fluids.
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All authors Paolo Molignini, M. A. Caracanhas, V. S. Bagnato, Barnali Chakrabarti
Statistical Mechanics · Cross-listed from quant-ph
Superradiant Phase is a Finite Size Effect in Two-photon Processes
Fabrizio Ramírez, David Villaseñor, Nahum Vázquez et al. (+1 more)
Two-
photon light-matter interactions exhibit distinctive features such as spectral collapse. The two-
photon Dicke model has been reported to exhibit a superradiant phase which could be useful in
quantum applications. Here we show that this superradiant phase is not a genuine thermodynamic phase but a finite-size effect. Combining analytical and numerical analyses, we demonstrate that the superradiant region shrinks with increasing system size and disappears in the thermodynamic limit, while spectral collapse remains. Our results clarify the nature of superradiant conditions in two-
photon systems and constrain its realization in
quantum platforms.
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All authors Fabrizio Ramírez, David Villaseñor, Nahum Vázquez, Jorge G. Hirsch
Statistical Mechanics · Cross-listed from hep-th
Timelike Entanglement Signatures of Ergodicity and Spectral Chaos
Rathindra Nath Das, Arnab Kundu and Nemai Chandra Sarkar
We investigate timelike
entanglement measures derived from the spacetime density kernel in the Rosenzweig-Porter model and show that they sharply diagnose both eigenvector ergodicity and spectral chaos. For several
Hilbert-space bipartitions, we compute the second Tsallis
entropy, the
entanglement imagitivity that quantifies non-Hermiticity, and Schatten-norm diagnostics of the kernel. The imagitivity and Frobenius norm exhibit rapid growth and high late-time plateaus in the ergodic regime, are suppressed in the localized regime, and show intermediate behavior in the fractal phase. The real part of the second Tsallis
entropy displays a spectral form factor-like dip-ramp-plateau throughout the chaotic window and a suppressed ramp in the localized regime. We further introduce a kernel negativity, defined as the negative spectral weight of the Hermitian part of the kernel. This negativity equals the trace-norm distance to the set of positive semidefinite operators and the maximal witnessable negative quasiprobability, and its time-averaged value decreases across the ergodic-fractal-localized crossover in close correspondence with the fractal dimension.
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Strongly Correlated Electrons
Unifying Dirac Spin Liquids on Square and Shastry-Sutherland Lattices via Fermionic Deconfined Criticality
Andreas Feuerpfeil, Leyna Shackleton, Atanu Maity et al. (+3 more)
We present a fermionic gauge theory for deconfined
quantum criticality on the Shastry-Sutherland
lattice and reveal its shared low-energy field-theoretic structure with the square
lattice. Starting from an SU(2) $\pi$-flux parent state, we construct a continuum theory of Dirac spinons coupled to an SU(2) gauge field and adjoint
Higgs fields whose condensates drive transitions to a staggered-flux U(1)
spin liquid and a gapless $Z_{2}$ Dirac
spin liquid. While the Shastry-Sutherland
lattice permits additional
symmetry-allowed
fermion bilinears compared to the square
lattice, the
quantum field theories are identical up to additional irrelevant terms. Consequently, the
Higgs potential structure and the leading low-energy theory coincide with the square-
lattice case at the
quantum critical point. The SO(5) critical point is expected to realize conformal deconfined criticality: we analyze it in a large-
flavor expansion, calculate its critical exponents, and identify the Yukawa coupling between the
fermions and
Higgs fields as the relevant perturbation that destabilizes it, consistent with pseudocritical behavior observed in recent Monte Carlo studies. We show that the emergent SO(5) order parameter acquires a large anomalous dimension at the critical point, leading to strongly enhanced Néel and VBS susceptibilities-a hallmark of fermionic deconfined
quantum criticality consistent with numerical studies. Our results place recent numerical evidence for a gapless $Z_{2}$ Dirac
spin liquid on the Shastry-Sutherland
lattice within a controlled field-theoretic framework and demonstrate that fermionic deconfined criticality on the square
lattice-including critical exponents and stability-extends to frustrated
lattices with reduced
symmetry.
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All authors Andreas Feuerpfeil, Leyna Shackleton, Atanu Maity, Ronny Thomale, Subir Sachdev, Yasir Iqbal
Statistical Mechanics · Cross-listed from hep-th
On the Wilson-Fisher fixed point in the limit of integer spacetime dimensions
Bernardo Zan
The Wilson-Fisher fixed point defines a continuous family of interacting conformal field theories in non-integer dimensions. In integer dimensions, it is widely believed to lie in the same universality class as the critical Ising model. In this work, we revisit the identification between the Wilson-Fisher fixed point at integer dimensions and the Ising CFT. We argue that a literal equality between the two theories is incompatible with the emergence of Virasoro
symmetry in two dimensions. Instead, we propose that the Ising model emerges only as a subsector of the Wilson-Fisher fixed point. We support this scenario through a detailed study of the two-dimensional $O(n)$ model and by examining operators transforming in irreducible representations of the orthogonal group whose multiplicities become negative for integer values of the spacetime dimension. Finally, we comment on the implications of these results for attempts to construct a $d=2+\epsilon$ expansion starting from exact two-dimensional data.
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Mesoscale and Nanoscale Physics · Cross-listed from quant-ph
A Surface-Scaffolded Molecular Qubit
Tian-Xing Zheng, M. Iqbal Bakti Utama, Xingyu Gao et al. (+24 more)
Fluorescent
spin qubits are central building blocks of
quantum technologies. Placing these
qubits at surfaces maximizes coupling to nearby
spins and fields, enabling nanoscale sensing and facilitating integration with photonic and superconducting devices. However, reducing the dimensions or size of established
qubit systems without sacrificing the
qubit performance or degrading the coherence lifetime remains challenging. Here, we introduce a surface molecular
qubit formed by pentacene molecules scaffolded on a two-dimensional (2D) material, hexagonal boron nitride (hBN). The
qubit exhibits stable fluorescence and optically detected
magnetic resonance (ODMR) from cryogenic to ambient conditions. With fully deuterated pentacene, the Hahn-echo coherence reaches 22 $\mu$s and further extends to 214 $\mu$s under dynamical decoupling, outperforming state-of-the-art shallow NV centers in diamond, despite being positioned directly on the surface. We map the local
spin environment, resolving couplings to nearby
nuclear and electron
spins that can serve as auxiliary
quantum resources. This platform combines true surface integration, long
qubit coherence, and scalable fabrication, opening routes to
quantum sensing,
quantum simulation, and hybrid
quantum devices. It also paves the way for a broader family of 2D material-supported molecular
qubits.
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All authors Tian-Xing Zheng, M. Iqbal Bakti Utama, Xingyu Gao, Moumita Kar, Xiaofei Yu, Sungsu Kang, Hanyan Cai, Tengyang Ruan, David Ovetsky, Uri Zvi, Guanming Lao, Yu-Xin Wang, Omri Raz, Sanskriti Chitransh, Grant T. Smith, Leah R. Weiss, Magdalena H. Czyz, Shengsong Yang, Alex J. Fairhall, Kenji Watanabe, Takashi Taniguchi, David D. Awschalom, A. Paul Alivisatos, Randall H. Goldsmith, George C. Schatz, Mark C. Hersam, Peter C. Maurer
Superconductivity
Detecting half-quantum superconducting vortices by spin-qubit relaxometry
Gábor B. Halász, Nirjhar Sarkar, Yueh-Chun Wu et al. (+3 more)
Half-
quantum vortices in
spin-triplet
superconductors are predicted to harbor Majorana zero modes and may provide a viable avenue to topological
quantum computation. Here, we introduce a novel approach for directly measuring the half-integer-quantized
magnetic fluxes, $\Phi = h / (4e)$, carried by such half-
quantum vortices via
spin-
qubit relaxometry. We consider a superconducting strip with a narrow pinch point at which
vortices cross quasi-periodically below a
spin qubit as a result of a bias current. We demonstrate that the relaxation rate of the
spin qubit exhibits a pronounced peak if the
vortex-crossing frequency matches the transition frequency of the
spin qubit and conclude that the
magnetic flux $\Phi$ of a single
vortex can be obtained by dividing the corresponding voltage along the strip with the transition frequency. We discuss experimental constraints on implementing our proposed setup in
spin-triplet candidate materials like UTe$_2$, UPt$_3$, and URhGe.
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All authors Gábor B. Halász, Nirjhar Sarkar, Yueh-Chun Wu, Joshua T. Damron, Chengyun Hua, Benjamin Lawrie
Materials Science
Global Plane Waves From Local Gaussians: Periodic Charge Densities in a Blink
Jonas Elsborg, Felix Ærtebjerg, Luca Thiede et al. (+3 more)
We introduce ELECTRAFI, a fast, end-to-end differentiable model for predicting periodic charge densities in crystalline materials. ELECTRAFI constructs anisotropic Gaussians in real space and exploits their closed-form
Fourier transforms to analytically evaluate plane-wave coefficients via the Poisson summation formula. This formulation delegates non-local and periodic behavior to analytic transforms, enabling reconstruction of the full periodic charge density with a single inverse FFT. By avoiding explicit real-space grid probing, periodic image summation, and spherical harmonic expansions, ELECTRAFI matches or exceeds state-of-the-art accuracy across periodic
benchmarks while being up to $633 \times$ faster than the strongest competing method, reconstructing
crystal charge densities in a fraction of a second. When used to initialize DFT calculations, ELECTRAFI reduces total DFT compute cost by up to ~20%, whereas slower charge density models negate savings due to high inference times. Our results show that accuracy and inference cost jointly determine end-to-end DFT speedups, and motivate our focus on efficiency.
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All authors Jonas Elsborg, Felix Ærtebjerg, Luca Thiede, Alán Aspuru-Guzik, Tejs Vegge, Arghya Bhowmik
Materials Science · Cross-listed from physics.bio-ph
Controlled drug delivery from chitosan-coated heparin-loaded nanopores anodically grown on nitinol shape-memory alloy
M. Moradi, E. Salahinejad, E. Sharifi et al. (+1 more)
Nitinol (NiTi shape-
memory alloy) is an interesting candidate in various medical applications like dental, orthopedic, and cardiovascular devices, owing to its unique mechanical behaviors and proper biocompatibility. The aim of this work is the local controlled delivery of a cardiovascular drug, heparin, loaded onto nitinol treated by electrochemical anodizing and chitosan coating. In this regard, the structure, wettability, drug release kinetics, and
cell cytocompatibility of the specimens were analyzed in vitro. The two-stage anodizing process successfully developed a regular nanoporous layer of Ni-Ti-O on nitinol, which considerably decreased the sessile water contact angle and induced hydrophilicity. The application of the chitosan coatings controlled the release of heparin mainly by a diffusional mechanism, where the drug release mechanisms were evaluated by the Higuchi, first-order, zero-order, and Korsmeyer-Pepass models. Human umbilical cord endothelial
cells (HUVECs) viability assay also showed the non-cytotoxicity of the samples, so that the best performance was found for the chitosan-coated samples. It is concluded that the designed drug delivery systems are promising for cardiovascular, particularly stent applications.
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All authors M. Moradi, E. Salahinejad, E. Sharifi, L. Tayebi
Strongly Correlated Electrons
Comment on "Instability of the ferromagnetic quantum critical point and symmetry of the ferromagnetic ground state in two-dimensional and three-dimensional electron gases with arbitrary spin-orbit splitting"
D. Belitz and T.R. Kirkpatrick
Metallic
quantum ferromagnets in the absence of quenched disorder are known to generically undergo a first-order
quantum phase transition, avoiding the
quantum critical point that had originally been expected. This is due to soft modes in the underlying
Fermi liquid that lead to long-ranged correlations. These correlations in turn yield a nonanalytic dependence of the free energy on the magnetization even at a mean-field level that results in a fluctuation-induced first-order transition. Kirkpatrick and Belitz [Phys. Rev. Lett. 124, 147201 (2020)] have pointed out that one notable exception are non-centrosymmetric metals with a strong
spin-orbit interaction. In such materials the
spin-orbit interaction gives the relevant soft modes a mass, which inhibits the mechanism leading to a first-order transition. Miserev, Loss, and Klinovaja [Phys. Rev. B 106, 134417 (2022)] have claimed that this conclusion does not hold if electron-electron interactions in the particle-particle channel, or 2$\kF$ scattering processes, are considered. They concluded that this interaction channel leads to soft modes that are not rendered massive by the
spin-orbit interaction and again lead to a first-order
quantum phase transition. In this Comment we show that this conclusion is not correct in three-dimensional magnets if the screening of the interaction is properly taken into account.
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Strongly Correlated Electrons
Real-Time Iteration Scheme for Dynamical Mean-Field Theory: A Framework for Near-Term Quantum Simulation
Chakradhar Rangi, Aadi Singh and Ka-Ming Tam
We present a time-domain iteration scheme for solving the Dynamical Mean-Field Theory (DMFT) self-consistent equations using retarded Green's functions in real time. Unlike conventional DMFT approaches that operate in imaginary time or frequency space, our scheme operates directly with real-time quantities. This makes it particularly suitable for near-term
quantum computing hardware with limited
Hilbert spaces, where real-time propagation can be efficiently implemented via Trotterization or variational
quantum algorithms. We map the effective
impurity problem to a finite one-dimensional chain with a small number of bath sites, solved via exact diagonalization as a proof-of-concept. The hybridization function is iteratively updated through time-domain fitting until self-consistency. We demonstrate stable convergence across a wide range of interaction strengths for the half-filled Hubbard model on a Bethe
lattice, successfully capturing the metal-to-
insulator transition. Despite using limited time resolution and a minimal bath discretization, the spectral functions clearly exhibit the emergence of Hubbard bands and the suppression of spectral weight at the
Fermi level as interaction strength increases. This overcomes major limitations of two-site DMFT approximations by delivering detailed spectral features while preserving efficiency and compatibility with
quantum computing platforms through real-time dynamics.
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Statistical Mechanics
Anomalous transport in non-integrable classical field theories
Matija Koterle, Tomaz Prosen and Tianci Zhou
Anomalous KPZ
spin transport is well established in integrable non-Abelian
lattice models but has not been investigated in continuum field theories as discretization in numerics generally break the continuum theory's integrability. We show that finite temperature acts as a regulator that can restore anomalous transport over a broad time window. In a family of
spin field theories labeled by integer $n$, the $n = 1$ case is the Landau-Lifshitz model, whose numerical data shows
spin superdiffusion with Kardar-Parisi-Zhang (KPZ) scaling and, at lower temperature ballistic energy transport, whereas both observables are diffusive at high temperature. The non-integrable $n = 2$ case shows the same crossover. While Lyapunov analysis confirms the model's non-integrability, the structure of
spin-density space-time profiles suggests that long-lived
soliton-like trajectories exist at low temperature.
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Soft Condensed Matter
Effective interactions in active Brownian particles
Clare R. Rees-Zimmerman, C. Miguel Barriuso Gutierrez, Chantal Valeriani et al. (+1 more)
We report an approach to obtain effective pair potentials which describe the structure of two-dimensional systems of active Brownian particles. The pair potential is found by an inverse method, which matches the radial distribution function found from two different schemes. The inverse method, previously demonstrated via simulated
equilibrium configurations of passive particles, has now been applied to a suspension of active particles. Interestingly, although active particles are inherently not in
equilibrium, we still obtain effective interaction potentials which accurately describe the structure of the active system. Treating these effective potentials as if they were those of
equilibrium systems, furthermore allows us to measure effective chemical potentials and pressures. Both the passive interactions and active motion of the active Brownian particles contribute to their effective interaction potentials.
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All authors Clare R. Rees-Zimmerman, C. Miguel Barriuso Gutierrez, Chantal Valeriani, Dirk G. A. L. Aarts
Strongly Correlated Electrons
Magnetization Plateaus in the Spin-Orbit Coupled Bilayer Triangular Lattice Antiferromagnet Rb2Co2(SeO3)3
Shengzhi Zhang, Gabriel Silva Freitas, Vivien S. Zapf et al. (+8 more)
Geometric frustration among competing
spin exchanges can give rise to novel
quantum phases by enhancing fluctuations that drive
magnetic systems beyond the classical regime. We investigate the frustrated array of strongly correlated
spin dimers in the
bilayer triangular
lattice antiferromagnet \rcs{} under applied
magnetic fields. A cascade of magnetization plateaus appears at \(M/M_s = 1/3, 1/2, 2/3,\) and \(5/6\), together with a weak anomalous feature near \(M/M_s = 1/6\), in fields up to 60 T. Concurrent changes in magneto-dielectric response follows the plateau boundaries. The finite slope of each plateau and the absence of a zero-field gap in our ultralow-temperature ac susceptibility down to 20 mK indicate broken \(U(1)\)
spin-rotation
symmetry. A minimal
bilayer-dimer model treated with bond operator representation reproduces the low-field sequence only when \(U(1)\)
symmetry is explicitly lifted by
spin-orbit-driven, bond-dependent anisotropy. Near saturation, a projected triangular pseudospin model accounts for the high-field plateaus with modest further-neighbor interactions. These results demonstrate that anisotropic exchange arising from
spin-orbit-coupled moments is essential for stabilizing the full plateau hierarchy in \rcs{}, a mechanism overlooked in previous interpretations of Co-based triangular
bilayers.
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All authors Shengzhi Zhang, Gabriel Silva Freitas, Vivien S. Zapf, Minseong Lee, Wonjune Choi, Shi-Zeng Lin, Tong Chen, Collin Broholm, Xianghan Xu, Robert J. Cava, Eun Sang Choi
Mesoscale and Nanoscale Physics
Interband State Transfer in Double-Gated Bilayer Graphene at High Electric Field
Margherita Melegari, Brian Skinner, Ignacio Gutierrez-Lezama et al. (+1 more)
The band structure of Bernal-stacked
bilayer graphene can be tuned using double-gated transistors to apply a perpendicular electric field that generates an interlayer potential energy difference $\Delta$. Dielectric breakdown limits the operation of conventional devices to the $\Delta \ll t_\perp \simeq 360$ meV regime. We employ double ionic gating to reach fields past $ 1$ V/nm, for which $\Delta > t_\perp$. We find that for $\Delta \simeq t_\perp$, the
evolution of the longitudinal resistance ($R_{xx}$) peak as a function of applied gate voltages undergoes a sharp change in slope, exhibiting a pronounced "knee". Increasing $\Delta$ past the "knee" results in an unusual
evolution transport properties: the peak in $R_{xx}$ decreases in magnitude, it exhibits a splitting concomitant with multiple sign reversals of the
Hall resistance, and hysteresis in the peak position emerges. We explain the observed phenomenology in terms of in-gap bound states, whose energy strongly depends on the perpendicular electric field, and crosses the mid-gap level for sufficiently large $\Delta > t_\perp$. The phenomenon causes large changes in the electronic density of in-gap states that profoundly affect the
evolution of the chemical potential. Our experimental results and their interpretation reveal unique aspects of the physics of in-gap states in Bernal
bilayer graphene and demonstrate that double ionic gating enables investigating the large-$\Delta$ regime, which has remained experimentally inaccessible so far.
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All authors Margherita Melegari, Brian Skinner, Ignacio Gutierrez-Lezama, Alberto F. Morpurgo