Superconductivity
Possible Pairing Symmetry of BaPtAs$_{1-x}$Sb$_{x}$ with an Ordered Honeycomb Network
Tsuyoshi Imazu, Naoya Furutani, Tadashi Adachi et al. (+3 more)
We investigate the possible pairing
symmetry of superconducting $\rm{BaPtAs}_{1-\it{x}}\rm{Sb}_{\it{x}}$ solid solution with an ordered-honeycomb network of Pt and pnictogens. A spontaneous internal
magnetic field below the superconducting transition temperature is observed in BaPtSb ($x = 1$) via the
muon-
spin relaxation measurement. We then pursue a scenario where the pairing
symmetry is changed from a time-reversal
symmetry-breaking (TRSB) state to another one by changing the Sb-concentration utilizing the effective tight-binding model obtained from the first principles calculations for $x = 0$ and $x = 1$, at which we see a significant difference in the shape of the dominant
Fermi surfaces. We find that the
chiral $d$-wave state with TRSB is most stable at $x = 1$, whereas the nodal $f$-wave or the conventional $s$-wave states without TRSB are competitive at $x = 0$.
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All authors Tsuyoshi Imazu, Naoya Furutani, Tadashi Adachi, Kazutaka Kudo, Yoshiki Imai, Jun Goryo
Soft Condensed Matter
Gaussian Process Regression-based Knowledge Distillation Framework for Simultaneous Prediction of Physical and Mechanical Properties of Epoxy Polymers
Sindu B.S. and Jan Hamaekers
Epoxy
polymers are widely used due to their multifunctional properties, but machine learning (ML) applications remain limited owing to their complex 3D molecular structure, multi-component nature, and lack of curated
datasets. Existing ML studies are largely restricted to simulation data, specific properties, or narrow constituent ranges. To address these limitations, we developed an informed Gaussian Process Regression-based Knowledge
Distillation (GPR-KD) framework for predicting multiple physical (glass transition temperature, density) and mechanical properties (elastic modulus, tensile strength, compressive strength, flexural strength, fracture energy, adhesive strength) of thermoset epoxy
polymers. The model was trained on experimental literature data covering diverse monomer classes (9 resins, 40 hardeners). Individual GPR models serve as teacher models capturing nonlinear feature-property relationships, while a unified neural network student model learns distilled knowledge across all properties simultaneously. By encoding the target property as an input feature, the student model leverages cross-property correlations. Molecular-level descriptors extracted from SMILES representations using RDKit create a physics-informed model. The framework combines GPR interpretability and robustness with deep learning scalability and generalization. Comparative analysis demonstrates superior prediction accuracy over conventional ML models. Simultaneous multi-property prediction further improves accuracy through information sharing across correlated properties. The proposed framework enables accelerated design of novel epoxy
polymers with tailored properties.
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Disordered Systems and Neural Networks · Cross-listed from stat.ML
EB-RANSAC: Random Sample Consensus based on Energy-Based Model
Muneki Yasuda, Nao Watanabe and Kaiji Sekimoto
Random sample consensus (RANSAC), which is based on a repetitive sampling from a given
dataset, is one of the most popular robust estimation methods. In this study, an energy-based model (EBM) for robust estimation that has a similar scheme to RANSAC, energy-based RANSAC (EB-RANSAC), is proposed. EB-RANSAC is applicable to a wide range of estimation problems similar to RANSAC. However, unlike RANSAC, EB-RANSAC does not require a troublesome sampling procedure and has only one hyperparameter. The effectiveness of EB-RANSAC is numerically demonstrated in two applications: a linear regression and maximum likelihood estimation.
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Materials Science
Ferroaxial magnets: time-reversal-even mirror symmetry violation from spin order
Hikaru Watanabe, Yue Yu, Jin Matsuda et al. (+2 more)
We investigate ferroaxial magnets, a new class of
spin-order-driven multiferroic magnets in which
magnetic ordering induces mirror-
symmetry breaking while preserving both time-reversal and spatial-inversion
symmetries. These systems exhibit a ferromagnet-like axial anisotropy that allows optical control of the ferroaxial polarization, while their macroscopic time-reversal
symmetry makes them attractive for
antiferromagnetic spintronics. Using
spin crystallographic group analysis, we identify the candidate materials and the nonrelativistic ferroaxial nature stemming from the strong exchange splitting of magnets. Furthermore, a
symmetry-based identification shows
magnetic materials that host ferroaxial order and metallic conductivity, realizing the ferroaxial metal state that undergoes a ferroaxial phase transition while remaining metallic. As a direct probe for the ferroaxial metal, we propose a third-order nonlinear
Hall effect originating from the transverse coupling between the electric field and Berry
curvature dipole mediated by the ferroaxial anisotropy. Our results establish ferroaxial magnets as a platform for nonrelativistic multiferroicity and spintronic applications.
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All authors Hikaru Watanabe, Yue Yu, Jin Matsuda, Daniel F. Agterberg, Ryotaro Arita
Materials Science
Xe gas bubble re-solution in U-10Mo nuclear fuel
ATM Jahid Hasan, Linu Malakkal, Mathew Swisher et al. (+1 more)
The U.S. High-Performance Research Reactor program aims to convert high-power research reactors from highly enriched uranium to low-enriched uranium using a monolithic U-10Mo fuel design. A critical aspect of U-10Mo fuel performance is fission gas bubble behavior. These bubbles grow by trapping gas atoms (particularly Xe) but can disintegrate via irradiation-induced "re-solution". The interplay between the trapping and re-solution rates governs bubble
evolution, impacting fuel performance and safety. In this study, binary collision approximation (BCA) and molecular dynamics (MD) simulations were performed to quantify the Xe gas bubble re-solution rate in U-10Mo fuel. First, the energy loss of fission fragments (FFs) through electronic and
nuclear stopping was evaluated. The effect of electronic stopping on re-solution was then analyzed using MD simulations coupled with the two-temperature model. Results indicate that thermal spikes generated by electronic stopping do not contribute to gas bubble re-solution in U-10Mo. To quantify re-solution due to
nuclear stopping, BCA simulations of FFs in U-10Mo were performed to obtain the average FF incidence probability, energy, and angle as a function of distance from the FF origin. Subsequent simulations assessed FF–bubble interactions in U-10Mo for different FF energies and bubble radii. From these analyses, an overall re-solution rate $b$ was calculated at
equilibrium bubble pressure per unit fission rate density, yielding values ranging from $4.4 \times 10^{-26}$ m$^3$/fission for the largest bubbles to $8.8 \times 10^{-25}$ m$^3$/fission for the smallest. The effect of bubble pressure on the re-solution rate was also evaluated, revealing an inverse relationship between the two.
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All authors ATM Jahid Hasan, Linu Malakkal, Mathew Swisher, Benjamin Beeler
Mesoscale and Nanoscale Physics
Crystallizing electrons with artificially patterned lattices
Trevor G. Stanfill, Daniel N. Shanks, Michael R. Koehler et al. (+6 more)
Wigner
crystals are typically confined to ultralow temperatures where thermal motion is frozen out. Moiré superlattices in twisted two-dimensional materials have extended their stability to higher temperatures and densities, but rely on delicate stacking that fixes the
lattice geometry and limits tunability. Here we demonstrate a lithographic approach that bypasses these constraints. Using high-resolution nanofabrication, we pattern a nanoscale triangular
lattice directly into a
graphene gate integrated with a monolayer MoSe2
semiconductor. This engineered potential landscape localizes electrons into generalized Wigner
crystal states that persist up to 15 K and densities of 2X10^12 cm-2, representing an order of magnitude improvement over pristine monolayer MoSe2. Gate-voltage control allows real-time switching between stable and unstable crystalline states, with the latter exhibiting
stochastic telegraph noise from nearly degenerate configurations. This work demonstrates the ability of this platform to transform Wigner
crystals from fragile, static phases into reconfigurable
quantum matter.
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All authors Trevor G. Stanfill, Daniel N. Shanks, Michael R. Koehler, David G. Mandrus, Takashi Taniguchi, Kenji Watanabe, Vasili Perebeinos, Brian J. LeRoy, John R. Schaibley
Statistical Mechanics
Impact of currents on non-equilibrium coexistence in chemically driven mixtures
E. Meyberg, J.F. Robinson and T. Speck
Virtually every biological function emerges through the organization of molecules in time and space. Consequently, a major challenge in statistical physics is to uncover the universal principles governing macromolecular self-organization within the crowded, non-
equilibrium environment of the
cell. Here, we investigate a class of models where molecules maintain a conserved total concentration but can switch "identities", thereby modulating their intermolecular interactions. By enforcing thermodynamic consistency via the local detailed balance condition, we derive the steady-state criteria determining coexisting concentrations in a binary mixture. For non-constant transition rates and using a sharp-interface approximation, we obtain jump conditions that generalize Gibbs' coexistence criteria of equal pressure and chemical potential. We demonstrate that these jumps balance the chemical potential differences of individual species against their currents, which are confined to the interfacial region.
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Soft Condensed Matter
Theory of hybrid defects, with coupled orientational order parameters, on flat and curved surfaces
Lincoln Paik and Jonathan V. Selinger
Many physical systems involve two types of orientational order, which are coupled together. For example, ferroelectric nematic
liquid crystals have coupled polar and nematic order, and tilted hexatic phases have coupled polar and hexatic order. In these systems, defect structures can be quite complex. Here, we investigate phases with two types of two-dimensional orientational order, $m$-atic and $n$-atic, where $m$ and $n$ are two distinct integers. We simulate these phases in a flat disk with strong radial anchoring, and on a spherical surface, because both of these geometries require the presence of defects. If the coupling between the two types of order is weak, then the defects are connected by a network of diffuse walls, and the system forms a stable domain structure. As the coupling increases, the domain walls become sharper and shorter. For very strong coupling, the higher-order defects merge into the lower-order defects, forming stretched defect cores.
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Superconductivity
Real-time detection of critical slowing-down at the superconducting phase transition
Guillermo Nava Antonio, Théo Courtois, Corentin Pfaff et al. (+5 more)
We employ optical pump-THz probe spectroscopy to chart the ultrafast superconductivity suppression in NbN over a broad range of excitation fluences. Our measurements uncover a pronounced lengthening of the superconductivity quenching time when the absorbed optical energy is close to the condensation energy of the
superconductor, which constitutes a non-
equilibrium analog of critical slowing-down on a timescale comparable to that of superconducting fluctuations. Time-dependent Ginzburg-Landau simulations reproduce this behavior and ascribe it to the flattening of the free energy landscape at the dynamical phase transition boundary. Our findings represent a direct observation in real time of slowed-down superconductivity dynamics in proximity to a critical point and open a pathway for investigating out-of-
equilibrium critical phenomena with time-resolved THz spectroscopy.
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All authors Guillermo Nava Antonio, Théo Courtois, Corentin Pfaff, KM Shivangi Shukla, Asle Sudbø, Stéphane Mangin, Thomas Hauet, Chiara Ciccarelli
Mesoscale and Nanoscale Physics
Annihilation of Dirac points and its topological obstruction in a photonic Kagome lattice
Zhaoyang Zhang, Matthieu Finck, Changchang Li et al. (+7 more)
Dirac points (DPs) are topological singularities that determine the extraordinary properties of two-dimensional materials. They are generally classified by discrete topological invariants, which determine the possibility of DPs' annihilation upon their collision. Here, we study the behaviors of DPs within a photonic Kagome
lattice created in atomic vapor. With optically engineering the potential difference among three sites constituting the Kagome unit
cell while preserving time-reversal
symmetry and the stability of an isolated DP, the DPs move in reciprocal space. By employing conical diffraction to measure their position and the topological invariant (Euler number), we demonstrate an obstruction to DPs' annihilation during collision and a transition to a case where the Euler number changes and annihilation occurs. Such topological transition is induced by a non-Abelian frame rotation of the eigenstates around the Brillouin zone
torus. The associated conversion of the DP quaternionic charges during their motion explains the change of Euler number.
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All authors Zhaoyang Zhang, Matthieu Finck, Changchang Li, Shun Liang, Jerome Dubois, Yumin Tian, Jiahao Wen, Yanpeng Zhang, Guillaume Malpuech, Dmitry Solnyshkov
Soft Condensed Matter
The landscape of instabilities versus shear angle in simulations
Chloe W. Lindeman and Sidney R. Nagel
We argue that, in order to appreciate fully how disordered solids fail under sufficiently large strains or thermal noise, a material should be regarded as a network of potentially interacting instabilities occurring along different directions of forcing. We develop a tool for simulations with periodic boundary conditions that allows strains to be applied at a continuously variable angle, $\theta$. This reveals an underlying landscape which consists of lines of instabilities in two dimensions. A modified polar plot provides a visualization of this strain landscape while also allowing a graphic measure of an instability's quadrupolar structure. Many lines persist over a broad angular range of applied strain; some pass through one another; others change continuously with angle or end by smoothly decreasing their magnitudes to zero. Appropriate paths through phase space allow instabilities to be circumvented and hence avoided entirely. We explain this by examining hysterons, i.e., instabilities that undo themselves upon reversing shear direction, and show that as the end of an instability line is approached, the separation between the forward and backward instabilities vanishes.
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Mesoscale and Nanoscale Physics
Advanced architectures for coupling III-V nanowires to photonic integrated circuitry
Edith Yeung, Kataryna Sorensen, David B. Northeast et al. (+4 more)
This work implements a hybrid device based on a
semiconductor quantum dot embedded within a nanowire to bridge a non-continuous curved waveguide structure. The geometry takes advantage of evanescent coupling between the photonic structures to recover single
photons emitted from both outputs of the device. Auto- and cross-correlation measurements were performed on different output facets of the device. We demonstrate single-
photon emission from both ends of the nanowire for both neutral, X and XX, and charged X-, excitonic complexes. We further demonstrate the cascaded XX-X emission by collecting each complex from a different facet. This work lays the foundation for on-chip architectures which utilize multi-directional integration of
quantum emitters.
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All authors Edith Yeung, Kataryna Sorensen, David B. Northeast, Maziyar Milanizadeh, Philip J. Poole, Robin L. Williams, Dan Dalacu
Superconductivity
Ambient-pressure 151-K superconductivity in HgBa2Ca2Cu3O8+{\delta} via pressure quench
Liangzi Deng, Thacien Habamahoro, Artin Safezoddeh et al. (+10 more)
Superconductivity has been a vigorously researched topic since its discovery in 1911. Raising the superconducting transition temperature (Tc) has been the main driving force behind such long-sustained efforts due to its potential for impacting humanity and the fundamental knowledge gained from understanding this macroscopic coherent
quantum state at high temperatures. The successful development of high-Tc superconductivity will make possible extraordinarily efficient generation, delivery, and utilization of energy, and could also enable the development of controlled fusion while impacting other burgeoning fields like
quantum computation and
quantum electronics. However, progress has been hindered by a longstanding plateau in the record ambient-pressure Tc, unchanged since 1993. Subsequent significant advancements in Tc have been achieved only under high pressures, preventing the realization of superconductivity's full potential. To directly address this challenge, we developed a pressure-quench protocol (PQP) to stabilize pressure-induced/-enhanced superconducting states at ambient pressure. Here we achieve a record ambient-pressure Tc of 151 K in the cuprate HgBa2Ca2Cu3O8+{\delta} via PQP. The experimental results are further supported by synchrotron X-ray diffraction measurements and
phonon and electronic structure calculations. This breakthrough opens new avenues for stabilizing and exploring ambient-pressure high-Tc superconducting states and other
quantum states that have been previously only accessible under pressure, paving the way for deeper understanding and practical applications of high-Tc superconductivity and beyond.
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All authors Liangzi Deng, Thacien Habamahoro, Artin Safezoddeh, Bishnu Karki, Sudaice Kazibwe, Daniel J. Schulze, Zheng Wu, Matthew Julian, Rohit P. Prasankumar, Hua Zhou, Jesse S. Smith, Pavan R. Hosur, Ching-Wu Chu
Mesoscale and Nanoscale Physics · Cross-listed from quant-ph
Doppler-induced tunable and shape-preserving frequency conversion of microwave wave packets
Felix Ahrens, Enrico Bogoni, Renato Mezzena et al. (+7 more)
In superconducting electronics, the ability to control the frequency of microwave wave packets is crucial for several applications, such as the operation of superconducting
quantum processors and the readout of superconducting sensors. We introduce a new approach to microwave frequency conversion that harnesses a dynamic Doppler effect induced by a propagating front that separates regions of different phase velocities. Employing a high-kinetic-inductance superconducting transmission line in a travelling-wave geometry, we were able to implement frequency shifts of microwave wave packets at 500$\,$MHz and 4$\,$GHz of up to 3.7$\,$% while fully preserving their temporal shape. In contrast to conventional methods based on frequency-mixing, our Doppler-induced frequency-conversion method avoids spurious mixing products, is continuously tunable by a quasi-dc current amplitude, and allows to imprint arbitrary patterns on the instantaneous frequency profile of temporally long wave packets. By engineering transmission lines that allow for larger phase-velocity changes and/or by cascading multiple Doppler-induced frequency conversions, an unlimited amount of frequency shifting is in principle attainable. These features demonstrate the potential of our frequency-conversion technique as a promising tool for advanced control of microwave wave packets for different
quantum applications.
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All authors Felix Ahrens, Enrico Bogoni, Renato Mezzena, Andrea Vinante, Nicolò Crescini, Alessandro Irace, Andrea Giachero, Gianluca Rastelli, Iacopo Carusotto, Federica Mantegazzini
Materials Science
Structural flexibility dictates reactivity of single-atom catalysts
Jakub Planer, Dominik Hrůza, Tadeáš Lesovský et al. (+3 more)
Unravelling the origins of single-atom catalyst reactivity is a central challenge in heterogeneous catalysis research. A key question is whether the activity arises solely from atomic isolation or from distinct structural and electronic configurations of the single atoms. Here, we use precisely defined Fe-N$_3$ and Fe-N$_4$ model catalyst sites synthesized on an inert support to quantify the effect of coordination geometry on chemical reactivity. Both the Fe-N$_3$ and Fe-N$_4$ models have the same electronic configuration (high-
spin Fe$^{2+}$ with S=2), and even their d-orbital occupancies and positions with respect to
Fermi level are almost identical. Despite this electronic similarity, the adsorption energy of CO differs by more than 0.6 eV between the Fe-N$_3$ and Fe-N$_4$ sites, as indicated by density functional theory computations and confirmed by atomically-resolved scanning tunneling microscopy experiments. We trace this reactivity difference to the structural flexibility of the Fe-N$_3$ sites, which allows strengthening of the Fe 3d$_{xz/yz}$-CO 2${\pi}$* back-bonding by lifting the Fe atom from the -N$_3$ plane. These results demonstrate that coordination geometry plays a crucial role in defining the reactivity of single-atom catalysts, and that such effects cannot be predicted by analysis of the sites' electronic structures alone.
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All authors Jakub Planer, Dominik Hrůza, Tadeáš Lesovský, Ayesha Jabeen, Jan Čechal, Zdeněk Jakub
Materials Science
First-principles study of doping influence on twin formation in Ni-Mn-Ga nonmodulated martensite
Petr Šesták, Martin Heczko, Ladislav Straka et al. (+2 more)
We investigate how chemical substitution reshapes the energetics of twin formation in non-modulated (NM) Ni-Mn-Ga martensite. Using density functional theory, we compute generalized planar fault energy (GPFE) curves for the $(101)[10\bar{1}]$ shear system in stoichiometric Ni$_{2}$MnGa and in a set of doped supercells containing Cu, Co, Fe, or Zn on different sublattices. The GPFE landscape is used as a microscopic descriptor of twinning behavior: the first barrier reflects intrinsic stacking-fault formation (twin nucleation), whereas subsequent barriers govern twin thickening and boundary motion. We find that the impact of dopants is strongly site dependent. Substitutions Cu$\rightarrow$Mn, Cu$\rightarrow$Ni, Co$\rightarrow$Ni, and Zn$\rightarrow$Mn lower the nucleation barrier and generally soften the GPFE profile, indicating more favorable conditions for twin formation and propagation; these cases also correlate with a reduced tetragonality $c/a$, which implies a smaller twinning shear and a reduced energetic cost of twin formation. In contrast, Cu$\rightarrow$Ga, Co$\rightarrow$Mn, Co$\rightarrow$Ga, Fe$\rightarrow$Ga, and Zn$\rightarrow$Ga increase GPFE barriers and hinder twinning, even though such substitutions are often used to enhance martensite stability and raise $T_{m}$. Fe$\rightarrow$Mn leaves barrier heights largely unchanged, while Fe$\rightarrow$Ni produces an anomalous GPFE response indicative of unstable twin configurations. Finally, inspired by the nanotwinning characterization of 10M/14M modulation, we link the depth of the two-layer nanotwin minimum to modulation stability. The substitutions Fe$\rightarrow$Mn, Cu$\rightarrow$Ni, and Zn$\rightarrow$Mn result in a lower energy minimum compared to the structure without the double-layered twin. The other studied substitutions favor the twin-free NM structure.
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All authors Petr Šesták, Martin Heczko, Ladislav Straka, Alexei Sozinov, Martin Zelený
Disordered Systems and Neural Networks · Cross-listed from quant-ph
Distributed Quantum Computing via Adaptive Circuit Knitting
K. Grace Johnson, Aniello Esposito, Gaurav Gyawali et al. (+5 more)
Distributing
quantum workloads over many
Quantum Processing Units (QPUs) is a crucial step in scaling up
quantum computers toward practical
quantum advantage due to the limitations in size of a single QPU. In the absence of high-fidelity
quantum interconnects,
circuit knitting could provide a path to computing certain properties of large
quantum systems on many QPUs of limited size in a distributed fashion using only classical communication.
Circuit knitting partitions large
quantum circuits into manageable sub-
circuits, however, reconstructing observables in a straightforward manner comes at an exponential cost in sampling and classical post-processing. To mitigate the overhead this technique incurs, we introduce an Adaptive
Circuit Knitting (ACK) method that finds efficient partitions of
quantum circuits by discovering regions of minimal
entanglement between subsystems. We simulate 1D and 2D disordered mixed-field Ising models up to 60
qubits and show that the ACK approach can reduce
circuit knitting sampling overheads by up to four orders of magnitude for observables of interest. We highlight our parallel GPU-accelerated implementation and discuss the need for efficient classical simulators to enable distributed
quantum algorithm development. Our techniques could enable efficient distribution of
quantum simulation for both near-term and fault-tolerant architectures.
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All authors K. Grace Johnson, Aniello Esposito, Gaurav Gyawali, Xin Zhan, Rohit Ganti, Namit Anand, Raymond G. Beausoleil, Masoud Mohseni
Soft Condensed Matter
Recent Modeling Advances in Dense Suspension Rheology
Orhun Ayar, Bhargav Sriram Siddani, Ishan Srivastava et al. (+1 more)
Dense suspensions of particles dispersed in
liquids are central to industrial and geophysical processes and serve as model systems for out-of-
equilibrium soft matter. At high particle concentrations, they exhibit stress-dependent rheology, including discontinuous shear thickening and shear jamming, arising from frictional contacts. Nonlinear physics arises from the interplay among direct contacts, interfacial chemistry, and fluid-mediated hydrodynamics. The relative importance of these mechanisms depends on the particle properties and flow conditions, making predictive modeling inherently multi-scale and, therefore, computationally challenging. Recent advances in computational methods have transformed our ability to simulate the physics of dense suspensions across different scales. In this Perspective, we primarily focus on state-of-the-art simulation frameworks that integrate the mechanics of dry granular materials, mediated by contact friction, with suspension hydrodynamics to provide predictive models of dense suspension rheology. We highlight recent computational developments for simulating dense, predominantly non-Brownian suspensions in the viscous limit at varying levels of fidelity, ranging from particle-resolved to continuum models, as well as models that investigate their mesoscale organization during flow. Together, these approaches reveal a hierarchical structure in which microscale constraints give rise to mesoscale frictional networks that ultimately govern the macroscopic flow. While our emphasis is on dense suspensions governed by near-field hydrodynamics and frictional interactions, we also briefly discuss complementary grid-based methods that can account for complex geometries and particle properties, and also enable continuum-scale descriptions.
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All authors Orhun Ayar, Bhargav Sriram Siddani, Ishan Srivastava, Abhinendra Singh
Statistical Mechanics · Cross-listed from quant-ph
Theory of the Matchgate Commutant
Piotr Sierant, Xhek Turkeshi and Poetri Sonya Tarabunga
In
quantum information theory and statistical physics,
symmetries of multiple copies, or replicas, of a system play a pivotal role. For
unitary ensembles, these
symmetries are encoded in the replicated commutant: the
algebra of operators commuting with the ensemble across $k$ replicas. Determining the commutant is straightforward for the full
unitary group, but remains a major obstacle for structured, computationally relevant
circuit families. We solve this problem for matchgate
circuits, which prepare fermionic Gaussian states on $n$
qubits. Using a Majorana
fermion representation, we show that operators coupling different system copies generate the orthogonal Lie
algebra $\mathfrak{so}(k)$, endowing the space of invariants with rich and tractable structure. This underlying
symmetry decomposes the matchgate commutant into irreducible sectors, which we completely resolve via a Gelfand–Tsetlin construction. We provide an explicit orthonormal basis of the matchgate commutant for all $k$ and $n$, together with a formula for its dimension that grows polynomially in $n$. Furthermore, we characterize the commutant of the Clifford–matchgate subgroup, showing that restricting to signed permutations of Majorana modes yields a commutant that qualitatively diverges from the matchgate case for $k \geq 4$ replicas. Ultimately, our orthonormal basis turns algebraic classification into a working toolbox. Using it, we derive closed-form expressions for matchgate twirling channels and a fermionic analogue of Weingarten calculus, the projector encoding all moments of the Gaussian state orbit, state and
unitary frame potentials, the average nonstabilizerness of fermionic Gaussian states, a systematic hierarchy of non-Gaussianity measures, and a fermionic de Finetti
theorem.
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Mesoscale and Nanoscale Physics · Cross-listed from quant-ph
Absence of Charge Offset Drift in a Transmon Qubit
Adria Rospars, Hector Hutin, Yannick Seis et al. (+8 more)
Superconducting
quantum circuits are sensitive to their electrostatic environment: uncontrolled charges accumulating on the electrodes of a Josephson junction shift the energy levels of a
qubit, perturbing its operation and restricting their design. This effect is captured by a single parameter - the charge offset - whose slow, unpredictable drift has proven difficult to eliminate in practice. Here, we report a tantalum-based transmon
qubit in which the charge offset remains pinned at zero over nearly three months of measurements, including two thermal cycles, with no observable compromise to the
qubit lifetime. This exceptional stability disappears in later cooldowns, indicating a fragile mechanism at play. We attribute it to the inductance of a thin superconducting layer inadvertently formed in parallel with the Josephson junction during fabrication. X-ray surface spectroscopy suggests this layer arises from an incomplete wet-etch of tantalum on sapphire. Deliberately engineering such a layer offers a route to eliminating charge-offset drift in superconducting
circuits more broadly.
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All authors Adria Rospars, Hector Hutin, Yannick Seis, Cristóbal Lledó, Réouven Assouly, Romain Cazali, Rémy Dassonneville, Ambroise Peugeot, Alexandre Blais, Audrey Bienfait, Benjamin Huard
Materials Science
Optimal Experimental Design for Reliable Learning of History-Dependent Constitutive Laws
Kaushik Bhattacharya, Lianghao Cao and Andrew Stuart
History-dependent constitutive models serve as macroscopic closures for the aggregated effects of micromechanics. Their parameters are typically learned from experimental data. With a limited experimental budget, eliciting the full range of responses needed to characterize the constitutive relation can be difficult. As a result, the data can be well explained by a range of parameter choices, leading to parameter estimates that are uncertain or unreliable. To address this issue, we propose a
Bayesian optimal experimental design framework to quantify, interpret, and maximize the utility of experimental designs for reliable learning of history-dependent constitutive models. In this framework, the design utility is defined as the expected reduction in parametric uncertainty or the expected information gain. This enables in silico design optimization using simulated data and reduces the cost of physical experiments for reliable parameter identification. We introduce two approximations that make this framework practical for advanced material testing with expensive forward models and high-dimensional data: (i) a Gaussian approximation of the expected information gain, and (ii) a surrogate approximation of the Fisher information
matrix. The former enables efficient design optimization and interpretation, while the latter extends this approach to batched design optimization by amortizing the cost of repeated utility evaluations. Our numerical studies of uniaxial tests for viscoelastic solids show that optimized specimen geometries and loading paths yield image and force data that significantly improve parameter identifiability relative to random designs, especially for parameters associated with
memory effects.
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Strongly Correlated Electrons
Limitations of Avila-inspired theory in the diamond chain with quasiperiodic disorder
Manish Kumar, Ivan M. Khaymovich and Auditya Sharma
The mobility edges (MEs) that separate localized, multifractal and ergodic states in energy are a central concept in understanding Anderson localization. In this work we study the effect of several mutually commensurate quasiperiodic frequencies on the mobility edge formation. We focus on the example of the addition of a constant offset to the quasiperiodic potential of the one-dimensional all-bands-flat diamond chain. We show that this additional offset can transform the anomalous mobility edges (AMEs), i.e. the energies, separating localized and multifractal states, into conventional mobility edges, separating localized from delocalized states. Also this appears to be the first example which shows the inability of Avila's global theory to analytically predict the ME location. We observe this both quantitatively, through the ME location mismatch, and qualitatively, via the formation of multiple MEs, not predicted by the theory.
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Soft Condensed Matter
Nonequilibrium assembly of Lennard-Jones particles on a sphere
Ivan Yu. Golushko, Olga V. Konevtsova, Daria S. Roshal et al. (+1 more)
Studying physical mechanisms and common
geometric principles underlying known spherical packings is crucial for rational design of synthetic nanocontainers. Here we model the growth of small spherical shells containing n<72 identical particles that have their own
curvature and interact with each other via the Lennard-Jones potential. The shell assembly is assumed to be nonequilibrium and sequential: at each step, a new particle is attached to the most energetically favorable position, after which the system relaxes. Along with well-known structures of the smallest icosahedral viral
protein shells, the proposed mechanism generates a wide range of shells exhibiting square-triangular surface order. Most of such shells are the models of synthetic or natural
protein complexes that have octahedral or tetrahedral
symmetries and perform various functions. We compare the obtained structures with those resulting from the
equilibrium assembly and corresponding to global energy minima. Also, we consider the temperature-dependent
stochastic assembly and use the double-minimum Lennard-Jones-Gauss potential to mimic anisotropic particle interactions.
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All authors Ivan Yu. Golushko, Olga V. Konevtsova, Daria S. Roshal, Sergei B. Rochal
Materials Science
Theory of orientation averaging in X-ray spectroscopies: understanding polarization dependence in a Cartesian tensor approach
Sihan Zhang, Oana Bunău, Marius Retegan et al. (+1 more)
X-ray absorption spectroscopy (XAS) and resonant inelastic X-ray scattering (RIXS) are powerful probes of electronic structure owing to their chemical and orbital selectivity. For powder samples, however, interpreting RIXS spectral intensities remains challenging as the measured signal is an average over all orientations. Existing theoretical treatments rely largely on spherical-tensor formalisms, which often involve complex derivations and case-specific analyses. Meanwhile, recent advances in
quantum-chemistry methods have made the evaluation of transition tensors in Cartesian coordinates both accurate and straightforward. Here, we present a general theoretical framework that translates Cartesian transition tensors into physically meaningful, orientation-averaged intensities for powder samples. The formalism allows predicting angular and polarization dependences ab initio for both XAS and RIXS and is extendable to other spectroscopies. The resulting predictions show excellent agreement with RIXS experimental data at the Ce L$_3$ edge.
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All authors Sihan Zhang, Oana Bunău, Marius Retegan, Pieter Glatzel
Superconductivity
Zero-field superconducting vortices and Majorana zero modes pinned by magnetic islands in correlated Rashba systems
Panagiotis Kotetes and Brian M. Andersen
We propose a route for pinning zero-field superconducting
vortices in systems which are exchange-coupled to
magnetic islands and feature Rashba
spin-orbit coupling. We consider islands with sizes which greatly exceed those of the
vortex cores and possess out-of-plane
magnetic moments. A crucial ingredient of our approach is that it considers
superconductors which are governed by
magnetic correlations without, however, exhibiting long range
magnetic order. The arising total magnetization is inhomogeneous and its gradients generate a nonzero vorticity in the superconducting phase.
Vortices become energetically stable due to the energy reduction brought about from the generation of electronic magnetization. Using our developed framework, we make concrete predictions for the emergence of zero-field
vortices and Majorana zero modes in superconducting topological
insulator surfaces and planar Rashba
superconductors. Our theory uncovers a nonstandard path for trapping composite
vortex-Majorana excitations in systems which appear to be within experimental reach.
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Strongly Correlated Electrons
Electronic correlations and dynamical screening with ab initio quantum embedding
Chia-Nan Yeh, Francesco Petocchi, Alexander Hampel et al. (+4 more)
First-principles descriptions of correlated
quantum materials require a simultaneous treatment of strong local many-body effects and nonlocal dynamical screening. We present an efficient fully self-consistent implementation of $GW$+EDMFT that combines nonlocal correlations at the $GW$ level with a non-perturbative treatment of local correlations within extended dynamical mean-field theory (EDMFT), with a well-defined double-counting correction and a self-consistently determined
impurity interaction. Self-consistency in both the Green's function and the dynamically screened interaction is essential for describing screening processes across energy scales. A key ingredient that makes it computationally feasible is the compression of two-particle correlation functions using interpolative separable density fitting (ISDF). Applying the scheme to the Mott
insulator SrMnO$_3$ and the correlated metal LaNiO$_3$, we show that the self-consistent effective local interaction resolves the overscreening inherent to constrained-RPA approaches. For SrMnO$_3$, this stabilizes a Mott-insulating state in quantitative agreement with experiment, while for LaNiO$_3$ local EDMFT corrections yield a quasiparticle mass enhancement consistent with ARPES. These results establish fully self-consistent $GW$+EDMFT as a reliable ab initio framework for strongly correlated
quantum materials.
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All authors Chia-Nan Yeh, Francesco Petocchi, Alexander Hampel, Philipp Werner, Olivier Parcollet, Antoine Georges, Miguel Morales
Soft Condensed Matter · Cross-listed from quant-ph
Davide Rattacaso, Daniel Jaschke, Antonio Trovato et al. (+2 more)
Efficient sampling from ensembles of
Hamiltonian cycles is critical for predicting the thermodynamic properties of compact
polymers, with applications including modeling
protein and RNA folding and designing soft materials. Although classical Monte Carlo methods are widely regarded as the standard approach, their efficiency is strongly limited when applied to compact
polymers. In this work, we enable a quadratic speedup in the estimation of thermodynamic properties of maximally compact
polymers and heteropolymers by
quantum computation. To this end, we encode the target thermodynamic ensemble into the amplitudes of a
quantum state, i.e., a
quantum sample, which can be processed via amplitude amplification. Using
quantum equational
reasoning, we construct a local parent
Hamiltonian whose unique ground state realizes a
quantum sample of all
Hamiltonian cycles. This state can be prepared on
quantum hardware using ground-state preparation methods, such as
quantum annealing, and subsequently manipulated to generate
quantum samples of
polymers and heteropolymers at a target temperature. Finally, we approximate the
quantum sample as a tensor network, revealing an
entanglement area law. For fixed-width rectangular
lattices, we obtain a time-efficient and compact encoding of the full ensemble of
Hamiltonian cycles, enabling the efficient evaluation of expectation values, partition functions, and configuration probabilities via tensor contractions, without resorting to sampling.
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All authors Davide Rattacaso, Daniel Jaschke, Antonio Trovato, Ilaria Siloi, Simone Montangero
Strongly Correlated Electrons
Intrinsic longitudinal spin-conductivity from ferroaxial spin-symmetry breaking
Yue Yu, Jin Matsuda, Hikaru Watanabe et al. (+2 more)
The interplay of
antiferromagnetic order, momentum-dependent Bloch
spin-splitting, time-reversal (T), and parity (P)
symmetries in non-relativistic systems has emerged as a central theme for spintronics. Two well-known examples are P-preserving and T-violating altermagnets and P-violating and T-preserving odd-parity magnets. Here we examine a class of coplanar AFMs with a translation invariant vector
spin chiral (VSC) order that preserves both P and T
symmetries but breaks the non-relativistic
spin-rotational invariance. Naively, such a VSC order is not expected to exhibit unusual phenomena. Here we show that the
spin-rotational
symmetry breaking generated by this VSC order can take on multiple forms, including ferroaxial
symmetry breaking. We further show that these states allow for non-relativistic and non-dissipative purely longitudinal (or purely transverse)
spin-conductivities. These states also allow the generation of non-relativistic altermagnetic
spin-splittings through circularly polarized light. We identify 16 candidate materials in the Magndata database for which our theory is applicable and provide effective microscopic models and DFT-based results that highlight the large emergent
spin conductivities.
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All authors Yue Yu, Jin Matsuda, Hikaru Watanabe, Ryotaro Arita, Daniel F. Agterberg
Mesoscale and Nanoscale Physics
3D to 2D localization in supertwisted multilayers
Jeane Siriviboon and Pavel Volkov
We study the electronic properties of multilayer "spirals" of two-dimensional materials with continuously increasing twist angle. The electronic states are shown to undergo a universal 3D-to-2D transition on increasing the in-plane momentum ${\bf k}_\parallel$ away from the $\Gamma$ point. The states with $k_\parallel>k_c$ are localized along the z axis due to mismatch between electronic dispersions of the twisted layers, whereas those with $k_\parallel<k_c$ are extended. We support our results by mapping of the system on the Aubry-André model and deduce the experimental signatures of 3D to 2D localization in transport experiments.
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Materials Science · Cross-listed from hep-ph
All-electron dark matter-electron scattering with random-phase approximation dielectric screening and local field effects
Cyrus Dreyer, Rouven Essig, Marivi Fernandez-Serra et al. (+2 more)
Accurate predictions for dark matter-electron scattering in solids require an all-electron treatment together with a faithful description of dielectric screening beyond simple approximations. In particular, local field effects, arising from microscopic inhomogeneities of the electronic response, can significantly modify scattering rates across relevant momentum and energy scales. We present an all-electron framework for computing dark matter-electron scattering rates that incorporates dielectric screening at the random-phase approximation (RPA) level, including local field effects. Using crystalline silicon as a
benchmark, we show that local field effects play an important role both at large momentum transfers, spanning multiple Brillouin zones, and at low momentum near the plasmon resonance. We compute electron
recoil spectra and projected sensitivities for non-relativistic
halo dark matter and for boosted dark matter or other dark-sector particles, which are sensitive to the impact of local field effects in these high and low momentum regimes, respectively. We further present RPA dielectric functions including local field effects for Ge, GaAs, SiC, and diamond, enabling a systematic comparison across target materials. These developments are implemented in the open source code QCDark2.
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All authors Cyrus Dreyer, Rouven Essig, Marivi Fernandez-Serra, Megan Hott, Aman Singal