Materials Science
Interface stability of beta-Ga2O3 (100) on oxidized Si- and C-terminated 3C-SiC (001) substrates: a first-principles investigation
Marica Licciardi, Aldo Ugolotti, Emilio Scalise et al. (+1 more)
We provide a first-principles modeling of the beta-Ga2O3/3C-SiC interface that takes into account the reconstructions occurring at the 3C-SiC (001) surface by oxidation, aiming to mimic the actual deposition process under the best structural and thermodynamic conditions. Using density functional theory calculations, we systematically investigate the interface configurations between beta-Ga2O3 (100) and both Si- and C-terminated 3C-SiC (001) substrates, considering realistic oxidation states that form at the SiC surface prior to epitaxial growth. Our analysis evaluates different stacking sequences and atomic-scale bonding arrangements, computing adhesion energies for various interface geometries to determine their relative thermodynamic stability. This work addresses the critical need for understanding beta-Ga2O3 integration on substrates with superior thermal conductivity, providing a theoretical framework for optimizing heteroepitaxial growth conditions in ultra-wide-bandgap power electronics applications.
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All authors Marica Licciardi, Aldo Ugolotti, Emilio Scalise, Leo Miglio
Soft Condensed Matter
A label-free method to quantify early-stage amyloid aggregation via intrinsic phenylalanine fluorescence
Gaëlle Audéoud, Louis Moine, Laura Bonnecaze et al. (+5 more)
The aggregation of amyloid-forming peptides is a dynamic, complex process that underlies their diverse biological activities, from physiological functions to disease-associated dysfunctions. While the structure of fibrillar end-products is well-characterized for most amyloids, the heterogeneous and often transient oligomers, likely key in cytotoxicity, remain poorly investigated, especially for peptides with low-yield aromatic residues. Here, by exploiting and developing flow induced dispersion analysis in both peak and front modes, we demonstrate that intrinsic phenylalanine fluorescence can be harnessed to quantify the conversion of diffusing monomers into non-diffusing oligomers and fibrils. This approach is validated using PSM$\alpha$3, a tryptophan- and tyrosine-free peptide from S. aureus, known for its fast amyloid fibrillation and key roles in bacterial virulence. We indeed characterize its low-molecular-weight oligomers, and size
evolution from 2 to 10 nm over time. Importantly, to further validate the robustness of our front-mode approach, we apply it to hIAPP, a tyrosine-containing, tryptophan-free peptide, with critical outcome in type 2 diabetes. Our results overcome the limitations of traditional biochemical and biophysical amyloid assays by extending analysis from large oligomers and fibrils to small heterogeneous oligomers, under near-physiological conditions. This study thus offers a new analytical framework, thereby filling a critical gap in amyloid research, to probe the early stages of aggregation, key in the design of alternative therapeutics for amyloid-diseases.
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All authors Gaëlle Audéoud, Louis Moine, Laura Bonnecaze, Maxime Lavaud, Lucie Khemtemourian, Yacine Amarouchene, Thomas Salez, Marion Mathelié-Guinlet
Mesoscale and Nanoscale Physics
Transcendental momentum quantization in semiconducting Rashba nanowires and zero energy states in their normal and superconducting phase
Nico Leumer, Harald Schmid, Milena Grifoni et al. (+1 more)
We study finite system properties of the canonical low energy model for a semiconducting nanowire with Rashba
spin-orbit coupling. The case of an isolated wire as well as of one proximitized by an s-wave
superconductor are considered. Already for the normal wire, the presence of
spin-orbit coupling leads to eigenstates of the finite system composed of more than two momentum eigenstates. The quantization condition for the wavevectors is not that of a
quantum box, but given instead by a transcendental equation linking the involved wavevectors. For the wire with superconducting pairing, the presence of electron and hole channels complicates the composition of the eigenstates. In this case we derive an approximate quantization condition close to the phase boundary, and a condition for the appearance of exact zero energy states. It can be satisfied both in the topological and in the trivial phase. Both the trivial and topological zero energy states contribute to the linear transport through Andreev reflection and direct transmission processes, with their relative importance depending on the degree of the states' localization at the boundary.
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All authors Nico Leumer, Harald Schmid, Milena Grifoni, Magdalena Marganska
Strongly Correlated Electrons
Floquet product mode and eigenphase order
Felix Möckel, Harald Schmid and Felix von Oppen
We study the robustness of the Floquet
quantum Ising model against integrability-breaking perturbations, focusing on the phase hosting both Majorana zero and $\pi$ modes. A recent work [Phys. Rev. B 110, 075117, (2024)] observed that the Floquet product mode, a composite edge mode constructed from both Majorana operators, is considerably more robust than the individual Majorana edge modes. We analyze these strong modes from the point of view of the eigenphase order present in finite chains with open boundary conditions. As a result of the Majorana modes, all Floquet eigenstates come in quadruplets in the integrable limit. We show that the robustness of the various modes as well as the behavior of the boundary
spin correlation functions can be understood in terms of the spectral statistics of these quadruplets in the presence of integrability-breaking perturbations.
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Materials Science
Bismuth-substituted Lutetium Iron Garnet Films with Giant Visible-Range Magneto-Optical Sensitivity
Megan H. Dransfield, Lukáš Flajšman, Matthijs H. J. de Jong et al. (+4 more)
Magneto-optical materials are indispensable across modern physics, serving as the foundation for precision
magnetic sensing, nonreciprocal photonics, and optical isolation technologies. The continual pursuit of materials with high Verdet constants has driven the development of garnet-based compounds exhibiting
giant magneto-optical sensitivity. In this work, we report the growth and comprehensive magneto-optical characterization of bismuth-substituted lutetium iron garnet (LuBiIG), a material that combines the large
spin-orbit coupling of bismuth with the
lattice stability of lutetium iron garnet. LuBiIG films with thicknesses between 85-220nm were grown by pulsed
laser deposition and characterized at room temperature over the 500-820nm wavelength range. The films exhibit an exceptionally high Verdet constant of up to -1.37e8 degree/meter/Tesla, peaking in the visible spectral range near 520nm. These results position LuBiIG as a highly sensitive magneto-optical material suitable for advanced cryogenic detection and hybrid
quantum applications.
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All authors Megan H. Dransfield, Lukáš Flajšman, Matthijs H. J. de Jong, Lars Peeters, Rhodri Mansell, Sebastiaan van Dijken, Laure Mercier de Lépinay
Superconductivity
Machine learning protocol to identify pairing symmetries via quasiparticle interference imaging in Ising superconductors
Adam Hložný, Jozef Haniš, Martin Gmitra et al. (+1 more)
Identifying the pairing
symmetry in unconventional
superconductors is essential for reliably characterizing their superconducting states and for enabling their integration into realistic
quantum devices. Here, we introduce a machine-learning-guided strategy to determine pairing
symmetry from quasiparticle interference (QPI) data, which integrates first-principles calculations, tight-binding modeling, and
symmetry-based classification of the superconducting pairing function. We demonstrate the approach on monolayer NbSe2 as an experimentally accessible probe of superconductivity in real materials, within a single scalar-
impurity Bogoliubov-de Gennes framework. Our analysis shows that the QPI-to-parameter inverse problem can be solved with high accuracy for most superconducting pairing channels in this setting, indicating that QPI carries rich, learnable information about the superconducting gap structure. Taken together, these results demonstrate that machine-learning-assisted QPI analysis provides a promising pathway for precise learning of superconducting pairing functions in
quantum materials.
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All authors Adam Hložný, Jozef Haniš, Martin Gmitra, Marko Milivojević
Statistical Mechanics · Cross-listed from q-bio.QM
Exact Discrete Stochastic Simulation with Deep-Learning-Scale Gradient Optimization
Jose M. G. Vilar and Leonor Saiz
Exact
stochastic simulation of continuous-time Markov chains (CTMCs) is essential when discreteness and noise drive system behavior, but the hard categorical event selection in Gillespie-type
algorithms blocks gradient-based learning. We eliminate this constraint by decoupling forward simulation from backward differentiation, with hard categorical sampling generating exact trajectories and gradients propagating through a continuous massively-parallel Gumbel-Softmax straight-through surrogate. Our approach enables accurate optimization at parameter scales over four orders of magnitude beyond existing simulators. We validate for accuracy, scalability, and reliability on a reversible dimerization model (0.09% error), a genetic oscillator (1.2% error), a 203,796-parameter gene regulatory network achieving 98.4% MNIST accuracy (a prototypical deep-learning multilayer perceptron
benchmark), and experimental patch-clamp recordings of ion channel gating (R^2 = 0.987) in the single-channel regime. Our GPU implementation delivers 1.9 billion steps per second, matching the scale of non-differentiable simulators. By making exact
stochastic simulation massively parallel and autodiff-compatible, our results enable high-dimensional parameter inference and inverse design across systems biology, chemical kinetics, physics, and related CTMC-governed domains.
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Statistical Mechanics
Thermodynamic Geometry of Classical and Quantum Statistics in the Relativistic Regime
Hosein Mohammadzadeh, Zahra Ebadi, Omid Yahyayi Monem et al. (+1 more)
We investigate the thermodynamic geometry of classical and
quantum ideal gases in the relativistic regime, with particular emphasis on the effects of particle mass and spatial dimensionality. Relativistic kinematics is incorporated through the full energy-momentum dispersion relation and the corresponding relativistic density of states. Using the Fisher-Rao information metric derived from the partition function, we analyze the thermodynamic
curvature for Maxwell-Boltzmann, Bose-Einstein, and
Fermi-Dirac statistics. Exact analytical expressions are obtained in two spatial dimensions, while the three-dimensional case is studied numerically. We show that the thermodynamic
curvature preserves its characteristic sign-positive for
bosons and negative for
fermions; even in the relativistic regime, reflecting effective attractive and repulsive statistical interactions, respectively. A distinctive relativistic effect is the shift of
curvature singularities from the non-relativistic critical point to a mass-dependent threshold at $\mu=mc^{2}$. In addition, the relativistic Bose-Einstein condensation temperature is evaluated, revealing explicit mass-dependent corrections to the non-relativistic result. These findings provide a unified
geometric perspective on relativistic statistical systems and clarify the interplay between
quantum statistics, relativistic kinematics, and critical behavior.
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All authors Hosein Mohammadzadeh, Zahra Ebadi, Omid Yahyayi Monem, Mohammad Hossein Naghizadeh Ardabili
Statistical Mechanics · Cross-listed from quant-ph
Krylov Distribution and Spectral Convergence of Quantum Fisher Information
Mohsen Alishahiha, Fatemeh Tarighi Tabesh and Mohammad Javad Vasli
We establish a direct correspondence between the Krylov hierarchy of
quantum Fisher information (QFI) and a Krylov-resolved decomposition of the symmetric logarithmic derivative (SLD). Building on the existing Krylov formulation of QFI, we show that the metrological information resolved at each Krylov level is exactly encoded in the incremental gain of the Lanczos hierarchy, giving the Krylov distribution a direct information-theoretic interpretation. A dual spectral formulation distinguishes the
Hilbert–Schmidt geometry used to construct the computational Lanczos hierarchy from the state-dependent geometry in which the SLD and QFI are naturally defined, and relates their associated Liouville measures. This distinction clarifies the origin of different convergence regimes: we recover exponential convergence for gapped spectra and derive an exact algebraic hard-edge convergence law for the Jacobi class, including the exact finite-order error and the marginal case separating finite from divergent QFI.
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Mesoscale and Nanoscale Physics
Yannik Brune, Marius Cizauskas and Marc Aßmann
Lasers serve as the fundamental workhorses of photonic
quantum technologies, with perfectly coherent light fields being essential for many protocols that generate nonclassical light, implement coherent control schemes, and initialize
qubits. However, no
laser is absolutely ideal and the implications of deviations from perfect coherence in
quantum technological tasks remain unclear. In this study, we theoretically and experimentally explore the
quantum coherence properties of
lasers from a resource theory perspective, establishing a significant connection between photonics,
quantum optics, and
quantum information science. We demonstrate that the maximum achievable
quantum coherence for
laser light is constrained by spontaneous emission and the purity of the dephased
laser field state. As a critical example application in
quantum information protocols, we show that the
quantum coherence of a
laser field with a given mean
photon number directly governs the maximum purity attainable when initializing a
qubit in a superposition state through resonant driving. Our findings are highly relevant for bridging applied physics and engineering with integrated photonic
quantum technologies and resource theories, paving the way for reliable benchmarking of various coherent light sources for applications in photonics and
quantum protocols.
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Statistical Mechanics
Two-parameter families of matrix product operator integrals of motion in Heisenberg spin chains
Vsevolod I. Yashin
Recently, Fendley et al. (2025) [arXiv:2511.04674] revealed a new simple way to demonstrate the integrability of XYZ Heisenberg model by constructing a one-parameter family of integrals of motion in the
matrix product operator (MPO) form with bond dimension 4. In this work, I report on the discovery of two-parameter families of MPOs that commute with Heisenberg
spin chain
Hamiltonian in case of various anisotropies (XXX, XXZ, XX, XY and XYZ). These solutions are connected by taking appropriate limits. For all cases except XYZ, I also write down Floquet charges of two-step Floquet protocols corresponding to the Trotterization. I describe a symbolic
algebra approach for finding such integrals of motion and speculate about possible generalizations and applications.
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Materials Science
Twist-induced altermagnetism in a metallic van der Waals antiferromagnet
Alberto M. Ruiz, Andrei Shumilin, Rafael González-Hernández et al. (+1 more)
Altermagnetism -a
magnetic state characterized by
spin-polarized electronic bands at zero net magnetization- offers a promising route for next-generation spintronic devices. In two-dimensional (2D) magnets, twist engineering enables its realization by breaking the combined inversion and time-reversal
symmetry (PT) while preserving
crystal symmetries that ensure the altermagnetic order. Here, by means of first-principles calculations and
symmetry analysis, we demonstrate that twist engineering applied to the recently synthesized metallic van der Waals antiferromagnet Co-doped
bilayer Fe$_3$GaTe$_2$ (Fe$_2$CoGaTe$_2$) provides a robust platform for altermagnetism. By twisting two layers of Fe$_2$CoGaTe$_2$, the PT
symmetry between opposite
spin sublattices is broken, resulting in a non-relativistic $i$-wave altermagnetic state with
spin splitting up to 138 meV. In the absence of
spin-orbit coupling (SOC), the electronic states are
spin-degenerate along six high-
symmetry directions, while the inclusion of SOC preserves this degeneracy along the three directions protected by twofold rotation axes. Furthermore, we unveil the microscopic mechanisms governing the
magnetic behavior in twisted Fe$_2$CoGaTe$_2$. Our results establish twist engineering and metallic Fe-based van der Waals antiferromagnets as versatile platforms to realize 2D van der Waals altermagnetism, with potential for designing high-efficiency ultrathin nanodevices.
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All authors Alberto M. Ruiz, Andrei Shumilin, Rafael González-Hernández, José J. Baldoví
Superconductivity
Anisotropic fully-gapped superconductivity in quasi-one-dimensional Li$_{0.9}$Mo$_6$O$_{17}$
M. J. Grant, T. M. Huijbregts, R. Nicholls et al. (+4 more)
Superconductivity in quasi-one-dimensional Li$_{0.9}$Mo$_6$O$_{17}$ emerges from an exotic, non-metallic normal state that exhibits signatures of Tomonaga-Luttinger
liquid behavior, emergent
symmetry and excitonic order. The high upper critical field, $H_{c2}$, in Li$_{0.9}$Mo$_6$O$_{17}$ suggests that that the favored pairing state is
spin-triplet in nature. Here, we report measurements of the
magnetic penetration depth down to $0.08\,\mathrm{K}$ ($T/T_c \lesssim 0.04$) and the specific heat down to $0.4\,\mathrm{K}$ ($T/T_c \lesssim 0.2$), and show that they are consistent with a moderately-coupled, fully-gapped superconducting state with marked gap anisotropy and a minimum ($\Delta_{\rm min} \simeq 0.4\,k_{\mathrm{B}}T_c$) occurring over a very narrow region in $k$-space. Combined with knowledge of $H_{c2}$, these measurements support the presence of a nodeless and possibly odd-parity
spin-triplet superconducting order parameter in Li$_{0.9}$Mo$_6$O$_{17}$.
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All authors M. J. Grant, T. M. Huijbregts, R. Nicholls, M. Greenblatt, P. Chudzinski, A. Carrington, N. E. Hussey
Statistical Mechanics · Cross-listed from quant-ph
Differentiable Maximum Likelihood Noise Estimation for Quantum Error Correction
Hanyan Cao, Dongyang Feng, Zixuan Lu et al. (+2 more)
Accurate noise estimation is essential for fault-tolerant
quantum computing, since decoding per formance depends critically on the fidelity of
circuit-level noise parameters. We introduce a differ entiable Maximum Likelihood Estimation (dMLE) framework that learns these parameters directly from experimental syndrome data using likelihood gradients, with no decoder in the training loop. Mapping syndrome likelihoods to statistical-mechanical models enables exact and efficient evalua tion via planar solvers for repetition codes and tensor networks (TNs) for surface codes, extending the exact treatment to code distance d = 5 with a small number of rounds, and, via spatial subsam pling combined with time-translation
symmetry, to larger codes and larger round counts. Across four experimental superconducting
datasets, dMLE reduces logical error rates by up to 30.6% for repetition codes. On the Sycamore d = 3 surface code, a TN decoder using the dMLE prior attains a logical error rate comparable to that reported for state-of-the-art AlphaQubit, using standard syndromes alone without auxiliary leakage data. On the larger d = 5 surface code the dMLE prior lowers the logical error rate of the TN and Tesseract decoders by 7.18% and 5.23% relative to a prior optimized by reinforcement learning; at d = 7 it lowers that of Tesseract by 4.56% and 4.83% in the X and Z bases.
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All authors Hanyan Cao, Dongyang Feng, Zixuan Lu, Cheng Ye, Feng Pan
Materials Science
Strain- and Field-Tunable Nonrelativistic Spin Splitting and Wave-Symmetry-Dependent Spin Transport in Twisted Bilayer Altermagnets
Shantanu Pathak and Saswata Bhattacharya
Magnetism-driven nonrelativistic
spin splitting (NRSS) provides a pathway toward efficient,
spin-orbit-free spintronics. In centrosymmetric two-dimensional antiferromagnets,
spin-polarized transport is
symmetry-forbidden due to the combined space-time inversion ($PT$)
symmetry. Here, by employing first-principles density functional theory and
spin-group
symmetry analysis, we demonstrate that twisting two
antiferromagnetic or
ferromagnetic monolayers of CoCl$_2$, AX$_2$ (A = Mn, V; X = Cl, Br, I), NiF$_2$, NiBr$_2$, FeS, CoS, MnTe$_2$, MnSe$_2$, and RuSe induces finite NRSS even in the absence of
spin-orbit coupling. The relative twist breaks $[C_2||P]$ and $[E||C_{nz}]$
symmetries, giving rise to momentum-dependent
spin polarization with distinct $d$-, $g$-, and $i$-wave altermagnetic patterns across the Brillouin zone. Using
symmetry-invariant $k\cdot p$ modeling, we extract linear
spin-splitting coefficients $\alpha^{(1)}$ ranging from 800-1100 meVÅ, comparable to SOC-induced Rashba-Dresselhaus strengths observed in noncentrosymmetric
semiconductors. An out-of-plane electric field ($\mathcal{E}_z$) introduces Zeeman-type band splitting up to 110 meV at 10 MV/cm, while biaxial strain tunes the NRSS magnitude nearly linearly without altering
symmetry. Crucially, the strain $u_{xx-yy}$ reduces the
spin point group
symmetry and drives reversible $g/i \rightarrow d$ wave-type transitions, resulting in finite
spin conductivity and an enhanced
spin-splitter angle (up to 18$^\circ$). These results extend the concept of altermagnetism to twisted
bilayer geometries and establish a general route for realizing exchange-driven, nonrelativistic
spin currents through
symmetry engineering without requiring heavy elements or
spin-orbit coupling.
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Mesoscale and Nanoscale Physics
Optical properties of single CsPbBr3 perovskite quantum dots synthesized by a modified ligand-assisted reprecipitation method
Marina Cagnon Trouche, Ernest Ruby, Margaux Cartier et al. (+5 more)
Colloidal perovskite
quantum dots (pQDs) are promising
quantum light emitters, and investigations at the single pQD scale have so far relied mostly on hot-injection synthesis, which requires precise temperature control and an inert atmosphere. While alternative synthesis routes under milder conditions are often associated with structural and surface defects that may have limited impact in ensemble measurements, demonstrating high optical quality at the level of individual pQDs constitutes the most stringent
benchmark for a new synthesis protocol. Here, we demonstrate that a modified ligand-assisted reprecipitation (LARP) approach yields CsPbBr3 pQDs showing state-of-the-art optical properties at the scale of single emitters. By combining an amine-mediated post-synthetic size-trimming strategy with didodecyldimethylammonium bromide (DDAB) ligands for enhanced surface passivation and colloidal stability, we obtain isolated pQDs with stable emission and minimal spectral
diffusion at cryogenic temperatures. Micro-photoluminescence experiments resolve the characteristic fine structure of the bright
exciton, its low-energy optical
phonon replicas, and the trion and biexciton states. Time-resolved and
photon correlation measurements show a ~90 ps lifetime and high purity single
photon emission, respectively. These results demonstrate that modified LARP synthesis constitutes an accessible alternative to hot injection, preserving the intrinsic excitonic and
quantum optical properties of individual pQDs while offering greater flexibility for post-synthetic ligand engineering, as exemplified here by the use of DDAB for surface passivation.
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All authors Marina Cagnon Trouche, Ernest Ruby, Margaux Cartier, Christophe Voisin, Maxime Vallet, Yannick Chassagneux, Cédric R. Mayer, Carole Diederichs
Superconductivity
Bridging atomic and mesoscopic length scales with Replica Scanning Tunneling Microscopy: Visualizing the atomic lattice of UTe$_2$ and the atomic scale superconducting gap modulations of FeSe close to micron length scales
Miguel Águeda Velasco, Jose D. Bermúdez-Pérez, Pablo García Talavera et al. (+16 more)
Scanning Tunneling Microscopy is a cornerstone technique for visualizing the electronic density of states with atomic resolution (typically below 0.1 nm). While the field of view of most STM setups extends up to a few microns, obtaining atomic resolution over these large areas is often impractical and excessively time-consuming. This is due to the need to acquire maps with a point number reaching $10^7$ or more with a full current or conductance vs voltage curve at each point. The standard procedure is to make large scale maps and then select small regions to zoom-in for high-resolution atomic scale analysis. However, this approach fails to address a question which is often critical: Does a specific atomic-scale modulation of the electronic density of states persist over much larger, mesoscopic length scales? Here we present a new method: Replica STM (R-STM), that overcomes this limitation, allowing the study of atomic-scale phenomena up to micron length scales. We obtained new large-area STM tunneling conductance maps in UTe$_2$ and FeSe, spanning areas over 200 nm in size. In these large scale maps we discovered periodic signals with wavelengths significantly exceeding interatomic distances. We show that these large-wavelength periodic signals are replicas of the underlying atomic-scale density of states modulations. R-STM leverages these replica signals to efficiently track atomic-scale features over large areas. We discuss the influence of phase slips, disorder and defects in the replicas. Our results suggest that atomic scale modulations of the superconducting density of states could persist over large length scales in FeSe. R-STM provides a new capability for STM to compare atomic scale with micrometer scale phenomena. The proof of principle of R-STM can be extended to any other scanning probe microscopy experiment where a periodic signal is traced as a function of position.
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All authors Miguel Águeda Velasco, Jose D. Bermúdez-Pérez, Pablo García Talavera, Raquel Sánchez-Barquilla, Jose Antonio Moreno, Juan Schmidt, Sergey L. Bud'ko, Paul C. Canfield, Georg Knebel, Midori Amano Patino, Gerard Lapertot, Jacques Flouquet, Jean Pascal Brison, Dai Aoki, Paula Giraldo-Gallo, Jose Augusto Galvis, Isabel Guillamón, Edwin Herrera Vasco, Hermann Suderow
Materials Science
Corrosion Evolution of T91 Steel in Static Lead-Bismuth Eutectic Under an Oxidising Environment
Minyi Zhang, Weiyue Zhou, Michael P. Short et al. (+3 more)
Understanding corrosion in
liquid metal-cooled
nuclear systems is essential in order be able to control it. While much literature exists detailing corrosion rates and mechanisms of structural materials in
liquid metals, much still remains to be discovered in new regimes of temperature, chemistry, and
impurity content. We focus on a less-studied set of conditions, specifically to investigate how
liquid lead-bismuth eutectic (LBE) corrodes ferritic/martensitic steels under high-temperature oxidizing conditions. We find that the
evolution of corrosion is determined by the formation of protection layer on the surface. The area without effective protection layer experiences oxidation along martensite grain boundaries, transitioning from intergranular attack to broader area corrosion as it progresses. The area a stable, coherent
oxide scale will slow the corrosion process and then is oxidized along pre-austenite grain boundaries. Both chromium and oxygen
diffusion play vital roles in this process. Most surprisingly, a layer of iron enriched body-centred cubic phase forms on the surface of LBE-corroded T91, contradicting previous studies, which reported only
oxide-based surface layers.
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All authors Minyi Zhang, Weiyue Zhou, Michael P. Short, Paul A.J. Bagot, Michael P. Moody, Felix Hofmann
Materials Science
Impact of strain on electron-phonon coupling of quantum emitters
Vytautas Žalandauskas, Rokas Silkinis, Lukas Razinkovas et al. (+6 more)
Defects in
semiconductors acting as optically active
spin qubits are intriguing objects of fundamental study and future technological developments. These defect-based color centers are of particular interest for detection and response to physical variations such as pressure and strain, or conversely – as we demonstrate the possibility of herein – pressure and strain can be utilized to manipulate
quantum emitter properties. To investigate how strain can alter the fundamental electron-
phonon interaction of
quantum defects, we employ the negatively charged silicon vacancy ($\mathrm{V_{Si}^{-}}$) in 4H-SiC as a use-case and study its vibrational structure under applied tensile and compressive uniaxial strain using first-principles calculations. We show that the strain variations of the emission spectrum can be explained by differing responses of bulk-like and quasi-localized vibrational modes. Importantly, the $\mathrm{V_{Si}^{-}}$ defect exhibits a strain-induced enhancement of the Debye-Waller factor under uniaxial tensile strain applied along the $a$-axis of 4H-SiC, thereby improving its performance as a
quantum emitter. The strain-dependent changes in the
phonon sideband enable distinguishing between compressive and tensile strain, opening up the possibility of
magnetic-field-free strain detection using only
spin-conserving transitions of solid-state
quantum emitters.
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All authors Vytautas Žalandauskas, Rokas Silkinis, Lukas Razinkovas, Ali Tayefeh Younesi, Minh Tuan Luu, Ronald Ulbricht, Ulrike Grossner, Lasse Vines, Marianne Etzelmüller Bathen
Strongly Correlated Electrons
Data-Driven Bath Fitting for Hamiltonian-Diagonalization Dynamical Mean-Field Theory
Taeung Kim, Jeongmoo Lee and Ara Go
We propose a machine-learning-based initialization method to overcome the nonlinear bath-fitting bottleneck in
Hamiltonian-diagonalization-based dynamical mean-field theory (HD-DMFT). In HD-DMFT, the continuous hybridization function is approximated by a finite set of bath-site energies and hybridization amplitudes, determined by minimizing a highly non-convex multivariable cost function. As the number of bath sites increases, the optimization becomes more sensitive to the initial guess and more prone to suboptimal local minima, which can slow or destabilize the DMFT self-consistency loop. We reformulate bath fitting as a supervised regression problem and train a kernel ridge regression model to predict near-optimal discrete bath parameters directly from the target hybridization function on the Matsubara axis. To ensure physical relevance and data diversity, we construct the training
dataset from tight-binding
Hamiltonians of layered-perovskite-like ruthenate models across systematically deformed structures, instead of relying on naive random parameter sampling, and obtain high-quality labels through fully converged conventional bath fitting. Time-reversal
symmetry is explicitly incorporated in both feature and target representations to reduce effective dimensionality and enforce physical consistency.
Benchmarks in the non-interacting limit show that the learned initialization systematically reduces the initial fitting error, decreases the number of conjugate-gradient iterations, and improves robustness against local minima over a wide range of bath sizes. We further demonstrate transferability to interacting DMFT calculations for $\mathrm{Sr_{2}RuO_{4}}$ solved with an adaptive-truncation
impurity solver, where the ML initialization yields consistently faster convergence than a
symmetry-preserving heuristic baseline while preserving the final fitted solution.
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Materials Science · Cross-listed from physics.optics
Profiling THz Beams With Off-Label Use of Infrared Microbolometric Cameras
Gabriel Nagamine, Carlo Vicario, Tariq Leinen et al. (+6 more)
Visualizing the spatial profile of light beams is essential for evaluating irradiance, characterizing beam quality, and achieving precise
alignment. In the optical spectral range, this is readily performed using silicon-based CCD and CMOS cameras. In the terahertz (THz) range, however, it typically requires specialized detectors with prohibitive costs. Here, we show that an infrared (IR) camera can be used outside of its labeled specifications to achieve similar performance as a dedicated microbolometric THz camera, at under 1% of the THz camera's cost. We compared the cameras by characterizing THz beam profiles from two sources: a pulsed broadband THz beam produced through optical rectification in organic
crystals, and a narrowband quasi-continuous-wave (quasi-CW) THz beam emitted by a
quantum cascade
laser. For the broadband THz radiation, the beam width measured by the two cameras differed by only ~ 6%, well within the pixel resolution limit, and in the narrowband quasi-CW case by just ~ 1.3%. Additionally, the IR camera exhibits a lower minimum detectable power (down to 1.5 THz) than the THz camera, while also maintaining a linear and polarization-independent responsivity. These results expand the applicability of conventional IR cameras to the THz range, suggesting that they will become routine tools for high-fidelity THz beam diagnostics and imaging in scientific and industrial applications.
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All authors Gabriel Nagamine, Carlo Vicario, Tariq Leinen, Guy Matmon, Marco Raffa, Mattias Beck, Giacomo Scalari, Adrian L. Cavalieri, Flavio Giorgianni
Materials Science
Coherent Phonon-Driven Band Renormalizations in 1T$'$-MoTe$_2$
Carl E. Jensen, Christoph Emeis, Stephan Jauernik et al. (+3 more)
Here, we investigate
phonon mode- and electron band-selective electron-
phonon couplings in centrosymmetric 1T$'$-MoTe$_2$ using time- and angle-resolved photoemission spectroscopy combined with frequency-domain analysis. Femtosecond near-infrared pulses excite coherent $A_g$-symmetric
phonon modes at 2.34 THz, 3.34 THz, and 3.86 THz, which manifest as oscillatory modulations in photoemission intensity and binding energy across the valence bands. Pixel-wise
Fourier analysis using recently developed methodologies reveals pronounced band selectivity with distinct coupling strengths for different electronic states and
phonon modes, enabling the evaluation of band-renormalization amplitudes in the range of few meV. Ab initio calculations qualitatively reproduce the experimentally observed coupling patterns and relative trends, demonstrating the capability of combined experimental and theoretical approaches to resolve ultrafast electron-
phonon interactions in
quantum materials.
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All authors Carl E. Jensen, Christoph Emeis, Stephan Jauernik, Petra Hein, Fabio Caruso, Michael Bauer
Materials Science
Rotational anisotropy Raman spectrometer for high-sensitivity crystallographic symmetry analysis
Di Cheng, Junxiang Li, Shizhuo Luo et al. (+2 more)
Raman spectroscopy stands as a cornerstone technique for probing collective excitations and emergent
quantum phases in solids. While polarization-resolved Raman scattering has been widely used to extract
symmetry information of eigenmodes, its conventional geometry suffers from significant limitations: it accesses only a subset of Raman tensor elements, enforces {\pi}-periodic intensity patterns that obscure intrinsic crystalline
symmetries, and lacks sensitivity to wavevector-dependent anisotropy. To overcome these constraints, here we introduce rotational-anisotropy Raman spectroscopy (RA-Raman). By measuring scattering intensity during full azimuthal rotation of the optical scattering plane at oblique incidence, this geometry enables complete reconstruction of the Raman tensor and reveals rich rotational anisotropy patterns essential for accessing subtle
symmetry information elusive to conventional methods. We developed a prototype instrument to validate this approach experimentally. For centrosymmetric
crystals, RA-Raman unambiguously identifies
phonon symmetry representations and determines crystallographic axes. In noncentrosymmetric
crystals, it resolves directional anisotropy and angular dispersion of
phonon-polaritons, enabling quantitative determination of the Faust-Henry coefficient and the separation of deformation-potential and electro-optic scattering contributions. By demonstrating unprecedented
symmetry-resolving power in standard
benchmark crystals, we establish RA-Raman as a powerful tool with far-reaching potential to discover and characterize
symmetry-breaking phases and topological excitations in
quantum materials.
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All authors Di Cheng, Junxiang Li, Shizhuo Luo, Zehao Chen, Xinwei Li
Materials Science
Improving Reliability of Machine Learned Interatomic Potentials With Physics-Informed Pretraining
Qianyu Zheng and Victor Fung
Machine learned interatomic potentials (MLIPs) have emerged as powerful tools for molecular dynamics (MD) simulations with their competitive accuracy and computational efficiency. However, MLIPs are often observed to exhibit un-physical behavior when encountering configurations which deviate significantly from their training data distribution, leading to simulation instabilities and unreliable dynamics, thus limiting the reliability of MLIPs for materials simulations. We present a physics-informed pretraining strategy that leverages simple physical potentials which can improve the robustness and stability of graph-based MLIPs for MD simulations. We demonstrate this approach by deploying a pretraining-finetuning pipeline where MLIPs are initially pretrained on data labelled with embedded atom model potentials and subsequently finetuned on the
quantum mechanical ground truth data. By evaluating across three diverse material systems (phosphorus, silica, and a subset of Materials Project) and three representative MLIP architectures (CGCNN, M3GNet, and TorchMD-NET), we find that this physics-informed pretraining consistently improves both prediction accuracy as well as stability in MD compared to the baselines.
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Strongly Correlated Electrons
Crossover from Quantum Chaos to a Reversed Quantum Disentangled Liquid in a Disorder-Free Spin Ladder
Hanieh Najafzadeh and Abdollah Langari
The mechanisms by which isolated interacting
quantum systems evade thermalization extend beyond disorder-induced many-body localization, encompassing a growing class of interaction-driven phenomena. We investigate a
spin-1/2 ladder with asymmetric XY leg couplings and tunable Ising interactions on the rungs, and identify the microscopic origin of quasi many-body localization (quasi-MBL) in this setting. Through a suite of diagnostics – including
entanglement dynamics, fidelity susceptibility, adiabatic gauge potential norms, level-spacing statistics and
entropy of eigenstates – we uncover a reentrant progression of dynamical regimes as the rung coupling Jz is varied: integrable behavior at Jz=0,
quantum chaos at intermediate Jz, and a robust nonthermal regime at strong coupling. In the latter regime, we demonstrate the emergence of a reversed
quantum disentangled
liquid (reversed-QDL), where the light species thermalizes while the heavy species remains localized. The strong-coupling limit further yields emergent local integrals of motion anchored in a fixed-point structure, providing a microscopic origin of the observed quasi-MBL dynamics. These results establish reversed-QDL as a distinct, disorder-free route to nonergodicity and broaden the classification of dynamical phases in
quantum matter.
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Mesoscale and Nanoscale Physics
Rashba Spin-Orbit Driven Topological Phase Transitions in Heterogeneous Armchair Honeycomb Nanoribbons
Hao-Ru Wu, Jhih-Shih You, Yiing-Rei Chen et al. (+1 more)
We investigate the emergence of nontrivial topological phases in heterogeneous armchair honeycomb nanoribbons arising from the interplay between structural geometry and Rashba
spin-orbit coupling (RSOC). The system consists of a central RSOC-active region sandwiched between two pristine segments, forming interfaces between topologically distinct phases. As the RSOC strength increases, interface states emerge and become localized at the junctions, exhibiting robustness against edge perturbations. For finite ribbon widths, the RSOC induces a closing and subsequent reopening of the bulk energy gap, signaling a topological phase transition without altering the underlying
lattice geometry. These findings reveal a route to engineering tunable topological states through the cooperative effects of interfacial structure and
spin-orbit interactions.
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All authors Hao-Ru Wu, Jhih-Shih You, Yiing-Rei Chen, Hong-Yi Chen
Strongly Correlated Electrons · Cross-listed from quant-ph
Calderbank-Shor-Steane codes on group-valued qudits
Ben T. McDonough, Jian-Hao Zhang, Victor V. Albert et al. (+1 more)
Calderbank-Shor-Steane (CSS) codes are a versatile
quantum error-correcting family built out of commuting $X$- and $Z$-type checks. We introduce CSS-like codes on $G$-valued qudits for any finite group $G$ that reduce to
qubit CSS codes for $G = \mathbb{Z}_2$ yet generalize the Kitaev
quantum double model for general groups. The $X$-checks of our group-CSS codes correspond to left and/or right multiplication by group elements, while $Z$-checks project onto solutions to group word equations. We describe
quantum-double models on oriented two-dimensional CW complexes (which need not cellulate a
manifold) and prove that, when $G$ is non-Abelian and simple, every $G$-covariant group-CSS code with suitably upper-bounded $Z$-check weight and lower-bounded $Z$-distance reduces to a CW
quantum double. We describe the codespace and logical operators of CW
quantum doubles via the same intuition used to obtain logical structure of surface codes. We obtain distance bounds for codes on non-Abelian simple groups from the graph underlying the CW complex, and construct intrinsically non-Abelian code families with asymptotically optimal rate and distances. Adding "ghost vertices" to the CW complex generalizes
quantum double models with defects and rough boundary conditions whose logical structure can be understood without reference to non-Abelian anyons or defects. Several non-invertible
symmetry-protected topological states, both with ordinary and higher-form
symmetries, are the unique codewords of simply-connected CW
quantum doubles with a single ghost vertex.
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All authors Ben T. McDonough, Jian-Hao Zhang, Victor V. Albert, Andrew Lucas
Other Condensed Matter
Anisotropic magnetoresistance and magnetic field-tunable Weyl nodes in Weyl metal SrRuO$_{3}$ thin films
Uddipta Kar, Akhilesh Kr. Singh, Elisha Cho-Hao Lu et al. (+8 more)
Weyl semimetals are a unique class of topological materials, possessing
Fermi-arc surface states and exhibiting the
chiral anomaly effect. The
chiral anomaly refers to non-
equilibrium charge transfer within a Weyl-node pair of opposite chirality under the condition of aligned electric and
magnetic fields ($\bf{E} \parallel \bf{B}$), leading to non-conserved
chiral charges and thus enhanced electrical conductivity. In experiments, such an enhanced conductivity due to the
chiral anomaly manifests as a negative longitudinal magnetoresistance (MR) when the external field $\bf{H}$ is applied along the bias current direction $\bf{I}$. In this work, we present rigorous $\phi$- and $\alpha$-dependent magnetotransport measurements to investigate such a negative longitudinal MR due to the
chiral anomaly in a sunbeam-shaped device fabricated from an untwinned Weyl metal SrRuO$_{3}$ (SRO) thin film. Here, $\phi$($\alpha$) represents the angle between $\bf{I}$ and the in-plane $\bf{H}$(SRO monoclinic [001]$_{\rm o}$). Unusual $\phi$ dependences of in-plane MR and
Hall effects were uncovered at low temperatures, accompanied by the emergence of the fourfold-symmetric component in the in-plane MR. These results indicate that the
chiral anomaly and resistivity anisotropy in SRO play important roles. In particular, the dramatic variation of Weyl nodes near the
Fermi level through
magnetic field manipulation of the magnetization orientation, as revealed by band structure calculations, is consistent with the observed in-plane MR and
Hall effect.
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All authors Uddipta Kar, Akhilesh Kr. Singh, Elisha Cho-Hao Lu, P.V. Sreenivasa Reddy, Fu-En Cheng, Wazid Ahmed, Song Yang, Chun-Yen Lin, Chia-Hung Hsu, Guang-Yu Guo, Wei-Li Lee
Strongly Correlated Electrons
Electron-electron and electron-phonon collision cross sections in CsV3Sb5
Charles Menil, Andrea Capa Salinas, Stephen D. Wilson et al. (+2 more)
AV3Sb5 (A=K, Rb, Cs) are kagome metals and
superconductors, attracting much recent
attention as nexus of multiple
quantum states. Here, through a systematic study of electric and thermal transport of CsV3Sb5, we identify it as a metallic
Fermi liquid with moderate electronic correlations ans strong electron-
phonon (e-ph) collision cross section. We observe contributions to the inelastic electrical resistivity, each dominating within a distinct temperature window. The prefactor of the T2 is consistent with the Kadowaki-Woods scaling for a
Fermi liquid with moderate correlation. By performing thermal conductivity measurements at zero and finite
magnetic field, we separate the electronic and the
lattice contributions to the thermal conductivity. The Wiedemann-Franz law is satisfied in the zero-temperature limit, while a downward deviation emerges at finite temperature due to the mismatch between the prefactors of the electrical and thermal quadratic resistivities, as reported in other metals. The Bloch-Grüneisen description of electron-
phonon scattering successfully accounts for both electronic thermal and electrical transport, indicating a remarkably large e-ph collision cross section in CsV3Sb5.
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All authors Charles Menil, Andrea Capa Salinas, Stephen D. Wilson, Benoît Fauqué, Kamran Behnia
Mesoscale and Nanoscale Physics
Temporal magnon-qubit Mach-Zehnder interferometer
Cody Trevillian, Steven Louis and Vasyl Tyberkevych
A temporal
magnon-
qubit Mach-Zehnder (MZ) interferometer is proposed. The interferometer is based on controllable
entanglement of a microwave
qubit and a magnonic state, achieved by application of a pulsed
magnetic field playing the role of a
magnon-
qubit temporal "beam splitter". Analogous to a typical MZ interferometer, the generated interference pattern of the final
qubit population carries information about the
magnon dynamics. One important application of the proposed scheme is the study of single
magnon decoherence. Interestingly, this scheme allows one to independently determine rates of two possible decoherence channels. This may help enable single
magnon state applications and answer fundamental questions of quasi-particle decoherence at single
quantum levels.
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