Mesoscale and Nanoscale Physics
Meissner-Ochsenfeld effect in semiconductor nanostructures with negative-U shells
N.T. Bagraev, N.A. Dovator, L.E. Klyachkin et al. (+1 more)
The Meissner-Ochsenfeld effect is demonstrated for the first time at room temperature. The diamagnetic response of a silicon nanostructure with edge channels covered by chains of negative U dipole boron centers is studied when put in (removed from) an external
magnetic field. Measurements of the diamagnetic response were carried out by recording the values of magnetization and generation currents. There is good agreement between the results of measurements of the generated internal
magnetic field obtained using a ferroprobe and recording the EMF induced by the occurrence of generation currents in an external
magnetic field, which determines the conditions of the mechanism of the nondissipative transport in the edge channels at room temperature, which is caused by their interactions with single carriers through negative U dipole boron centers. The interrelation of the magnetization hysteresis and the magnitude of the EMF induced by the occurrence of generation currents indicates the possibilities of the electrical registration of the Meissner-Ochsenfeld effect in nanostructures manufactured within the framework of the
Hall geometry.
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All authors N.T. Bagraev, N.A. Dovator, L.E. Klyachkin, A.M. Malyarenko
Statistical Mechanics
Equilibrium-like statistical mechanics in space-time for a deterministic traffic model far from equilibrium
Aryaman Jha, Kurt Wiesenfeld and Jorge Laval
Motivated by earlier numerical evidence for a percolation-like transition in space-time jamming, we present an analytic description of the transient dynamics of the deterministic traffic model elementary cellular automaton rule 184 (ECA184). By exploiting the deterministic structure of the dynamics, we reformulate the problem in terms of a height function constructed directly from the initial condition, and obtain an
equilibrium statistical mechanics-like description over the
lattice configurations. This formulation allows macroscopic observables in space-time, such as the total jam delay and jam relaxation time, as well as microscopic jam statistics, to be expressed in terms of
geometric properties of the height function. We thereby derive the associated scaling forms and recover the critical exponents previously observed in numerical studies. We discuss the physical implications of this space-time
geometric approach.
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Quantum Gases
W-SLDA Toolkit: A simulation platform for ultracold Fermi gases
Gabriel Wlazłowski, Piotr Magierski, Michael McNeil Forbes et al. (+1 more)
We present the W-SLDA Toolkit, a general-purpose software package for simulating ultracold
Fermi gases within the framework of density functional theory and its time-dependent extensions. The toolkit enables fully microscopic studies of interacting superfluid systems across the BCS-BEC crossover, including
spin-imbalanced configurations and arbitrary external geometries. It provides both static and time-dependent solvers capable of describing a broad range of phenomena in one-, two-, and three-dimensional settings. In addition, the toolkit incorporates functionality for solving the standard Bogoliubov-de Gennes equations for
fermions, extending its applicability to other physical systems such as
superconductors. The code is implemented in C with GPU acceleration and is optimized for hybrid CPU/GPU execution on modern high-performance computing platforms. It ensures scalability on leadership-class supercomputers, enabling fully three-dimensional simulations with large atomic numbers, and allows for direct
benchmarks of ultracold-atom experimental setups. Its modular architecture facilitates straightforward extensions, user customization, and seamless interoperability with other scientific software frameworks. Furthermore, an extensive collection of practical usage examples is provided through the integrated reproducibility packs functionality, ensuring transparency and reproducibility of computational results.
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All authors Gabriel Wlazłowski, Piotr Magierski, Michael McNeil Forbes, Aurel Bulgac
Materials Science
Tailoring Ultrathin Magnetic Multilayers at Terraced Topologically Insulating Interfaces for Perpendicularly Magnetized Domains
Benjamin A. Brereton, Soumyarup Hait, Ahmet Yagmur et al. (+8 more)
Topological
insulators and skyrmion-hosting,
chiral magnetic multilayers are two well-explored areas of modern condensed matter physics, each offering unique advantages for spintronics applications. In this paper, we demonstrate the optimization process for the growth of a Bi$_2$Se$_3$/buffer/[Pt/CoB/Ru]$_{\times N}$
heterostructure that combines these two material classes: the Bi$_2$Se$_3$ epilayer was grown by molecular beam epitaxy before transfer under ultrahigh
vacuum to a separate growth chamber where the polycrystalline metallic multilayer was sputter deposited. The structure of the samples was characterized by co-fitted X-ray and polarized
neutron reflectometry measurements and scanning transmission electron microscopy. Polarized
neutron models and standard magnetometry show that a buffer layer exceeding a critical thickness is required to obtain the desired uniform, perpendicular
magnetic anisotropy in every
magnetic layer in the multilayer. Samples with both Ta and Mo buffers were used requiring thicknesses of 1.5 and 0.9 nm respectively. In minimizing the Bi$_2$Se$_3$ terracing, buffered samples yield well-defined, out-of-plane,
magnetic domains suitable for
spin-orbit torque induced manipulation as determined by X-ray photoemission electron microscopy.
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All authors Benjamin A. Brereton, Soumyarup Hait, Ahmet Yagmur, Christy J. Kinane, Francesco Maccherozzi, Michele Conroy, Satoshi Sasaki, Thomas A. Moore, Sarnjeet S. Dhesi, Sean Langridge, Christopher H. Marrows
Materials Science
The role of absorption in three-dimensional electron diffraction dynamical structure refinement
Benjamin Colmey, Tiarnan A.S. Doherty, Shreshth A. Malik et al. (+1 more)
The role of absorption in 3D electron diffraction is established through analytical theory, simulation, and dynamical refinement. A two-beam expression for the absorbed integrated intensity in centrosymmetric
crystals is derived, showing that for $t/\xi_g \ll 1$ reflections follow a uniform exponential decay set by the mean absorptive potential $U_0'$. Many-beam simulations of both centrosymmetric and non-centrosymmetric
crystals reveal additional reflection-specific anomalous absorption beyond the uniform attenuation set by $U_0'$. Neglecting these effects in dynamical refinement of integrated intensities incurs an error that increases approximately linearly with thickness, with this error becoming more severe near zone axes. Dynamical refinements were performed on CsPbBr$_3$, quartz, and borane, with the inclusion of absorption yielding an improvement in $R_{\mathrm{obs}}$ from $6.4$ to $5.3$ % for CsPbBr$_3$ and negligible improvements for quartz and borane. Anomalous absorption may therefore be ignored for routine refinement of integrated intensities except in high-$Z$ materials at thicknesses approaching $\xi_g $.
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All authors Benjamin Colmey, Tiarnan A.S. Doherty, Shreshth A. Malik, Paul A. Midgley
Disordered Systems and Neural Networks
Structural coarse-graining enables noise-robust functional connectivity and reveals hidden inter-subject variability
Izaro Fernandez-Iriondo, Antonio Jimenez-Marin, Jesus Cortes et al. (+1 more)
Functional connectivity estimates are highly sensitive to analysis choices and can be dominated by noise when the number of sampled time points is small relative to network dimensionality. This issue is particularly acute in fMRI, where scan resolution is limited. Because scan duration is constrained by practical factors (e.g., motion and fatigue), many
datasets remain statistically underpowered for high-dimensional correlation estimation. We introduce a framework that combines
diffusion-based structural coarse-graining with spectral noise filtering to recover statistically reliable functional networks from temporally limited data. The method reduces network dimensionality by grouping regions according to
diffusion-defined communication. This produces coarse-grained networks with dimensions compatible with available time points, enabling random
matrix filtering of noise-dominated modes. We
benchmark three common FC pipelines against our approach. We find that raw-signal correlations are strongly influenced by non-stationary fluctuations that can reduce apparent inter-subject variability under limited sampling conditions. In contrast, our pipeline reveals a broader,
multimodal landscape of inter-subject variability. These large-scale organization patterns are largely obscured by standard pipelines. Together, these results provide a practical route to reliable functional networks under realistic sampling constraints. This strategy helps separate noise-driven artifacts from reproducible patterns of human
brain variability.
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All authors Izaro Fernandez-Iriondo, Antonio Jimenez-Marin, Jesus Cortes, Pablo Villegas
Strongly Correlated Electrons
Anisotropy, frustration and saddle point in the twisted Kagome antiferromagnet ErPdPb
Resham Babu Regmi, Sk Jamaluddin, Y. Lee et al. (+14 more)
The kagome
lattice, with its inherent
geometric frustration, provides a rich platform for exploring intriguing
magnetic phenomena and topological electronic structures. In reduced-
symmetry structures, such as twisted kagome systems involving rare earth elements, additional anisotropy can arise, enabling intriguing properties including
spin-ice states, magnetocaloric effects, noncollinear
magnetic ordering, and anomalous
Hall effect. Here, we report the synthesis of single
crystals of ErPdPb, which features a twisted kagome
lattice net of Er atoms within the hexagonal ZrNiAl-type structure, and we investigate its
magnetic, electronic, and thermal properties. The material exhibits
antiferromagnetic ordering below 2.2 K, consistently observed in
magnetic, transport, and heat capacity measurements. Magnetization measurements reveal 1/3 metamagnetic steps along the c-axis below the Néel temperature, suggesting an Ising-
spin-like state on the twisted kagome
lattice. A pronounced anisotropy between in-plane and out-of-plane resistivity is observed throughout the temperature range of 1.8-300 K, and the compound exhibits a significant frustration index of 13.6 (12.7) along the c-axis (ab-plane). Heat capacity measurements show a broad hump at 2.2 K, with an additional increase below 0.5 K. The anisotropic
magnetic properties are further explored through density functional theory (DFT) calculations, which suggest strong easy-axis anisotropy, consistent with experimental
magnetic measurements and
crystal-field model expectations, and quasi-one-dimensional bands and a
spin-split saddle point at the zone center.
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All authors Resham Babu Regmi, Sk Jamaluddin, Y. Lee, Hari Bhandari, Po-Hao Chang, Peter E. Siegfried, Abhijeet Nayak, Mohamed El Gazzah, Bence G. Márkus, Anna Nyáry, Zachary T. Messegee, Miya P. Zhao, Xiaoyan Tan, László Forró, Liqin Ke, Igor I. Mazin, Nirmal J. Ghimire
Statistical Mechanics · Cross-listed from nlin.CD
Chaos, the Critical Phenomenon in Phase Space: Feigenbaum Constants and Critical Exponents
Yonghui Xia and Hongtao Feng
Chaos in both dissipative systems and conservative systems is investigated on the approach of renormalization group. It is found that the chaos is regarded as the critical phenomenon of
equilibrium statistics in phase space. The two Feigenbaum constants in the period-doubling bifurcation systems correspond to two independent critical exponents, which are universal and can be adopted to distinguish the classes of chaos. For the conservative systems, due to the critical nature of the chaos, the isolated systems with different parameters are correlated in the phase space, and therefore the isolated system is no longer isolated in the phase space. The information of conservative systems is irreversibly lost over time, which leads to the increase
entropy in an isolated system, and the contradiction between the second law of thermodynamics and the reversibility of isolated systems can be resolved.
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Superconductivity · Cross-listed from quant-ph
Multiplexed microwave resonators by frequency comb spectroscopy
Angelo Greco, Jukka-Pekka Kaikkonen, Luca Chirolli et al. (+4 more)
Coplanar waveguide resonators are central to the thriving field of
circuit quantum electrodynamics. Recently, we have demonstrated the generation of a broadband microwave-frequency comb spectrum using a superconducting
quantum interference device (SQUID) driven by a time-dependent
magnetic field. Here, the frequency comb is used to spectroscopically probe a bank of coplanar microwave resonators, inductively coupled to a common transmission line, a standard
circuit with a variety of applications. We compare the resonator line shape obtained from signals synthesized at room temperature using conventional electronics with the radiation produced in the cryogenic environment by our source, showing substantial equivalence in the estimation of the resonator quality factors. To measure non-uniformly spaced resonant frequencies, we drive the generator with a bi-chromatic tone to generate intermodulation products. Such a dense frequency comb spectrum enables simultaneous addressing of a few resonators via frequency multiplexing. Finally, we discuss the criteria for achieving effective spectroscopic coverage of a given frequency bandwidth.
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All authors Angelo Greco, Jukka-Pekka Kaikkonen, Luca Chirolli, Alberto Ronzani, Jorden Senior, Francesco Giazotto, Alessandro Crippa
Materials Science · Cross-listed from quant-ph
Spin-active chlorine-related centers in 4H-SiC with telecom-band emissions
Danial Shafizadeh, Misagh Ghezellou, Viktor M. Bobal et al. (+5 more)
A photoluminescence (PL) and
magnetic resonance investigation of a defect in chlorine-implanted 4H-SiC is presented. This Cl-related center emits light at telecom wavelengths with zero-
phonon lines in the range 1350-1540 nm. Its four configurations exhibit stable PL spectra characterized by narrow zero-
phonon lines. For the two configurations that emit light at the C-band, a Debye-Waller factor in the range 22-25% is estimated. Optically detected
magnetic resonance confirms that the Cl-related center is
spin active and stable at room temperature with the zero-field splitting in the range of 1.0-1.4 GHz. The combined optical and
spin properties suggest this center to be a highly promising candidate for scalable
quantum networks.
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All authors Danial Shafizadeh, Misagh Ghezellou, Viktor M. Bobal, Lasse Vines, Jawad Ul-Hassan, Valdas Jokubavicius, Nguyen T. Son, Ivan G. Ivanov
Materials Science · Cross-listed from stat.ML
Cutting Through the Noise: On-the-fly Outlier Detection for Robust Training of Machine Learning Interatomic Potentials
Terry C. W. Lam, Niamh O'Neill, Christoph Schran et al. (+1 more)
The accuracy of machine learning interatomic potentials suffers from reference data that contains numerical noise. Often originating from unconverged or inconsistent electronic-structure calculations, this noise is challenging to identify. Existing mitigation strategies such as manual filtering or iterative refinement of outliers, require either substantial expert effort or multiple expensive retraining cycles, making them difficult to scale to large
datasets. Here, we introduce an on-the-fly outlier detection scheme that automatically down-weights noisy samples, without requiring additional reference calculations. By tracking the loss distribution via an exponential moving average, this unsupervised method identifies outliers throughout a single training run. We show that this approach prevents overfitting and matches the performance of iterative refinement baselines with significantly reduced overhead. The method's effectiveness is demonstrated by recovering accurate physical observables for
liquid water from unconverged reference data, including
diffusion coefficients. Furthermore, we validate its scalability by training a foundation model for organic chemistry on the SPICE
dataset, where it reduces energy errors by a factor of three. This framework provides a simple, automated solution for training robust models on imperfect
datasets across
dataset sizes.
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All authors Terry C. W. Lam, Niamh O'Neill, Christoph Schran, Lars L. Schaaf
Mesoscale and Nanoscale Physics
Unconventional magnetoelectric conductivity and electrochemical response from dipole-like sources of Berry curvature
Ipsita Mandal
We investigate the longitudinal magnetoelectric conductivity and nonlinear electrochemical response (ECR) of three-dimensional nodal-ring semimetals, including
vortex nodal-rings (VNRs) and $\mathcal{PT}$-symmetric nodal-rings (PTNRs), together with three-band
Hopf semimetals (HSMs), using the semiclassical Boltzmann formalism. The nodal-rings of the VNRs and PTNRs lie in the $k_z=0$ plane, whereas the nodal points of HSMs host isolated Berry-
curvature (BC) dipoles with axes along the $k_z$ direction. In VNRs, such dipoles may be viewed as forming a continuous distribution along the nodal-ring, connecting the two classes of systems. For collinear electric and
magnetic ($\mathcal{B}$) fields along the anisotropy axis $\boldsymbol {\hat{z}}$, the linear response is computed exactly and displays odd powers of $B_z$ for a single ring or node. For a two-node HSM with oppositely-oriented BC-dipole axes, these odd terms cancel in the sum. We analyse the nonlinear ECR, described by third-rank response tensors that relate the current to the combined action of an electric field and a chemical-potential gradient. The surviving tensor components are determined by the tilt direction of the bandstructure, and we obtain explicit results for simultaneous in-plane and axial tilts. A comparison of the three systems reveals a close correspondence between the responses of VNRs and HSMs, while PTNRs behave qualitatively differently. We attribute these similarities and differences to the
topology of the BC field, namely dipole-like sources in VNRs and HSMs versus the ring-confined BC structure of PTNRs.
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Materials Science
Flash annealing-engineered wafer-scale relaxor antiferroelectrics for enhanced energy storage performance
Yizhuo Li, Kepeng Song, Meixiong Zhu et al. (+11 more)
Dielectric capacitors are essential for energy storage systems due to their high-power density and fast operation speed. However, optimizing energy storage density with concurrent thermal stability remains a substantial challenge. Here, we develop a flash annealing process with ultrafast heating and cooling rates of 1000 oC/s, which facilitates the rapid crystallization of PbZrO3 film within a mere second, while locking its high-temperature microstructure to room temperature. This produces compact films with sub-grain boundaries fraction of 36%, nanodomains of several nanometers, and negligible lead volatilization. These contribute to relaxor antiferroelectric film with a high breakdown strength (4800 kV/cm) and large polarization (70 uC/cm2). Consequently, we have achieved a high energy storage density of 63.5 J/cm3 and outstanding thermal stability with performance degradation less than 3% up to 250 oC. Our approach is extendable to ferroelectrics like Pb(Zr0.52Ti0.48)O3 and on wafer scale, providing on-chip nonlinear dielectric energy storage solutions with industrial scalability.
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All authors Yizhuo Li, Kepeng Song, Meixiong Zhu, Xiaoqi Li, Zhaowei Zeng, KangMing Luo, Yuxuan Jiang, Zhe Zhang, Cuihong Li, Yujia Wang, Bing Li, Zhihong Wang, Zhidong Zhang, Weijin Hu
Superconductivity
Josephson tunneling through a Yu-Shiba-Rusinov state: Interplay of $\pi$-shifts in Josephson current and local superconducting order parameter
Andreas Theiler, Christian R. Ast and Annica M. Black-Schaffer
An
impurity hosting a
magnetic moment coupled to a conventional $s$-wave
superconductor gives rise to so-called Yu-Shiba-Rusinov (YSR) states with energies inside the superconducting gap. Depending on the coupling between the
impurity and the
superconductor, the system can have two distinct
quantum ground states separated by a
quantum phase transition (QPT). We investigate the interplay of two effects observed at the QPT. First, the tunneling supercurrent through the
impurity reverses its sign at the QPT, denoted as a $\pi$-shift in the current-phase relation. Secondly, the local superconducting order parameter at the
impurity site is suppressed and becomes negative at the QPT, generally termed a $\pi$-shift in the local superconducting order parameter. We find that both these effects are governed by the presence of the YSR state, however, they do not significantly depend or influence each other. In particular, we establish that the $\pi$-shift in the superconducting order parameter does not induce a $\pi$-shift in the tunneling Josephson current, nor can the Josephson current and its spatial behavior be used to directly probe the
impurity-induced changes in the local superconducting order parameter, which occur on a length scale substantially shorter than the superconducting coherence length.
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Materials Science
$d$-wave Surface Altermagnetism in Centrosymmetric Collinear Antiferromagnets
Ersoy Sasioglu, Ingrid Mertig and Samir Lounis
Broken inversion
symmetry at the surfaces of centrosymmetric collinear antiferromagnets lifts combined inversion and time-reversal
symmetry ($PT$) and can, in principle, enable nonrelativistic d-wave
spin splitting, termed surface altermagnetism. Combining
symmetry analysis with first-principles calculations, we show that surface inversion breaking, while necessary, is not sufficient for this effect. Surface altermagnetism emerges only when no antiunitary
symmetry survives at the surface that exchanges the two antiferromagnetically coupled surface sublattices and enforces
spin degeneracy. We demonstrate this mechanism explicitly for the centrosymmetric G-type antiferromagnets V$_3$Al and BaMn$_2$Sb$_2$, and contrast it with MnPt, where a sublattice-exchanging
symmetry survives at the surface in the form of translation-time-reversal
symmetry ($tT$), thereby preserving
spin degeneracy despite broken inversion
symmetry. The mechanism is shown to apply across multiple classes of centrosymmetric antiferromagnets and remains robust against
spin-orbit coupling, although relativistic
spin mixing in heavier-element compounds may reduce the observable
spin polarization. These results establish a
symmetry-based route toward realizing robust nonrelativistic momentum-dependent
spin polarization at
antiferromagnetic surfaces and interfaces.
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Materials Science
Emergent altermagnetism at surfaces of antiferromagnets: full symmetry classification and material identification
Colin Lange, Rodrigo Jaeschke-Ubiergo, Atasi Chakraborty et al. (+4 more)
We demonstrate the emergence of altermagnetism at the surfaces of antiferromagnets, vastly expanding the number of material candidates with altermagnetic characteristics and establishing a route towards two-dimensional altermagnetism through surface-induced
symmetry breaking. We do so by developing a surface
spin group formalism that fully classifies all surface
magnetic states and identifies altermagnetic surface
spin groups that can arise at the surfaces of antiferromagnets. We use this formalism to identify over 150
antiferromagnetic entries from the MAGNDATA database with at least one altermagnetic surface, often times with multiple such surfaces in the same material, and clarify the role of surface roughness and terraces. We illustrate this emergent phenomenon in a realistic Lieb
lattice-based minimal model and present ab initio calculations on two representative material candidates, $\text{NaMnP}$ and $\text{FeGe}_2$, exhibiting $d$-wave and $g$-wave surface altermagnetism, respectively. Our theory naturally resolves the contradiction of recent experimental reports of $d$-wave
spin splitting from ARPES measurements on metallic Lieb
lattice compounds such as KV$_2$Se$_2$O that have been shown to be
antiferromagnetic in the bulk. Hence, we establish a new paradigm for generating effectively two-dimensional altermagnetism by functionalizing the abundant material class of collinear antiferromagnets as viable platforms for controlled surface altermagnetism.
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All authors Colin Lange, Rodrigo Jaeschke-Ubiergo, Atasi Chakraborty, Xanthe H. Verbeek, Libor Šmejkal, Jairo Sinova, Alexander Mook
Materials Science · Cross-listed from quant-ph
Heterogeneous Optically-Detected Spin-Acoustic Resonance in Solid-State Molecular Thin-film
Kuan-Cheng Chen, Yongqiang Wen, Xiaotian Xu et al. (+7 more)
We report an implementation of
spin-acoustic resonance in pentacene thin films integrated on a high-quality-factor (high-Q) surface acoustic wave (SAW) resonator on a lithium niobate substrate. Heterogeneous optically detected
spin-acoustic resonance (HODSAR) is an optically detected
spin-resonance measurement in which the resonant drive is delivered mechanically by a surface acoustic wave (SAW). By leveraging the photo-excited triplet state of pentacene at room temperature, we demonstrate coherent
spin manipulation via acoustic driving under zero externally applied
magnetic field. The heterogeneously integrated device, referred to as HODSAR, utilizes
spin-
phonon coupling to achieve mechanically driven, zero-field
spin resonance, opening avenues for room-temperature mechanically addressable
spin control and device integration. We show that the high-Q multimode response of the SAW resonator enables spectrally selective acoustic addressing of triplet transitions near 105 MHz. Coherent control is evidenced by Rabi oscillations, with a Rabi frequency that increases linearly with the square root of the applied RF input power over the measured drive range, consistent with driven two-level dynamics under acoustic excitation. These results establish
spin-acoustic resonance in a heterogeneously integrated molecular thin-film platform and provide a quantitative basis for benchmarking mechanically mediated
spin control.
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All authors Kuan-Cheng Chen, Yongqiang Wen, Xiaotian Xu, Max Attwood, Jingdong Xu, Chen Fu, Sami Ramadan, Shang Yu, Sandrine Heutz, Mark Oxborrow
Superconductivity
Topological properties of spin block magnetic ladders in proximity of a superconductor: application to BaFe$_{2}$S$_{3}$
Shivam Yadav, Pascal Simon and Andrzej Ptok
Monoatomic chains with
magnetic order in proximity of a s-wave
superconductor can host Majorana edge modes. In this paper, we extend this idea to more complex
spin-block chains such as the BaFe$_{2}$S$_{3}$
magnetic material that has a
spin-ladder like structure. We investigate the topological phase diagram of such a system as function of the system parameters. We show that the coupling between chains within the ladder leads to the topological phase with a winding number larger than the sum of two single
magnetic chains. Furthermore, strong coupling between chains leads to fractal-like substructure in the topological phase diagram. By investigating the real space properties of such a system and particularly its edge modes, we find that the system spectrum contains several in-gap states that we analyze in detail.
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Mesoscale and Nanoscale Physics
Josephson diode and spin-valve effects on the surface of altermagnet CrSb
V.D. Esin, D.Yu. Kazmin, Yu.S. Barash et al. (+3 more)
We experimentally investigate charge transport in In-CrSb and In-CrSb-In proximity devices, which are formed as junctions between superconducting indium leads and thick single
crystal flakes of altermagnet CrSb. For double In-CrSb-In junctions, $dV/dI(B)$ curves are mirrored in respect to zero field for two
magnetic field sweep directions, which is characteristic behavior of a Josephson
spin valve. Also, we demonstrate Josephson diode effect by direct measurement of the critical current for two opposite directions in external
magnetic field. We interpret these observations as a joint effect of the
spin-polarized topological surface states and the altermagnetic
spin splitting of the bulk bands in CrSb. For a single In-CrSb interface, the superconducting gap oscillates in
magnetic field for both field orientations, which strongly resembles the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) behavior. FFLO is based on finite-momentum Cooper pairing, therefore, it is fully compatible with the requirements for the Josephson diode effect.
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All authors V.D. Esin, D.Yu. Kazmin, Yu.S. Barash, A.V. Timonina, N.N. Kolesnikov, E.V. Deviatov
Materials Science · Cross-listed from physics.app-ph
Germanium Thermophotovoltaic Devices Achieving 7.3% Efficiency Under High-Temperature Emission by Empirical Calorimetry
A. M. Medrano, E. Lopez, Pablo Garcia-Linares et al. (+6 more)
We report the first empirical efficiency measurement of germanium-based thermophotovoltaic devices under high-temperature, high-irradiance conditions using a high view-factor calorimetric setup. Two TPV
cell architectures were fabricated on p-type, highly doped (10^17 cm-3) Ge substrates, differing only in rear contact configuration. A standard device with a gold rear contact achieves a peak efficiency of 7.3 % and a power density of 1.77 W/cm2 at an emitter temperature of 1480 C, while a PERC-type device reaches 6.3 % efficiency and 1.22 W/cm2 at 1426 C. The superior performance of the standard device is attributed to lower series resistance, whereas the PERC design exhibits slightly higher efficiency at lower emitter temperatures (4.0 % vs. 3.8 % at 1150 C) due to enhanced rear-surface reflectivity. A detailed TPV model has been developed and validated across both device architectures. The model identifies out-of-band optical losses as the dominant efficiency-limiting mechanism, primarily caused by strong free-carrier absorption in the highly doped Ge substrate. Using this model, we predict device performance under idealized spectral conditions commonly assumed in prior literature. For a simulated AlN/W spectrally selective emitter, efficiencies as high as 22.3 % at 1800 C are obtained, consistent with previous semi-empirical predictions. In contrast, when previously reported Ge devices are modeled under the realistic graphite emitter spectrum used here, projected efficiencies decrease to as low as 8.1 % at 1480 C. These results show that earlier projections remain valid but idealized and underscore the importance of emitter spectral engineering and substrate optimization. Finally, we present the first direct comparison of Ge and InGaAs TPV devices under identical conditions, demonstrating the superior performance of InGaAs while confirming the cost-driven competitiveness of Ge.
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All authors A. M. Medrano, E. Lopez, Pablo Garcia-Linares, J. Villa, M. Gamel, M. Garin, I. Martin, C. Canizo, A. Datas
Materials Science
NMRPeak: a ready-to-use intelligent system for molecular structure elucidation enabled by synergistic cross-modal learning
Fanjie Xu, Jinyuan Hu, Jingxiang Zou et al. (+8 more)
One-dimensional
nuclear magnetic resonance (NMR) spectroscopy is essential for molecular structure elucidation in organic synthesis, drug discovery, natural product characterization, and metabolomics, yet its interpretation remains heavily dependent on expert knowledge and difficult to scale. Although machine learning has been applied to NMR spectrum prediction, library
retrieval, and structure generation, these tasks have evolved in isolation using simulated data and incompatible spectral representations, limiting their utility under real experimental scenarios. Here we present NMRPeak, a unified cross-modal learning system that integrates these three tasks through experimentally grounded design. We curate approximately 1.8 million experimental and simulated spectra to construct the largest
benchmark for NMR-based structure elucidation and systematically quantify the distribution shift between these domains. We introduce a chemically-aware adaptive tokenizer that dynamically balances discretization granularity to preserve spectral semantics while controlling vocabulary size, and an assignment-free peak-aware similarity metric that enables direct comparison between predicted and experimental spectra. Through a unified molecule-to-spectrum paradigm and synergistic coupling of prediction,
retrieval, and generation modules, NMRPeak achieves transformative performance on experimental
benchmarks: it overcomes the longstanding simulation-to-experiment gap in spectrum prediction while delivering over 95% top-1 accuracy in molecular
retrieval and approximately 75% top-1 accuracy in stereochemistry-aware de novo structure generation. These capabilities establish a foundation for automated, high-throughput molecular structure elucidation in organic synthesis, drug discovery, and chemical biology.
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All authors Fanjie Xu, Jinyuan Hu, Jingxiang Zou, Junjie Wang, Boying Huang, Zhifeng Gao, Xiaohong Ji, Weinan E, Zhong-Qun Tian, Fujie Tang, Jun Cheng
Soft Condensed Matter · Cross-listed from physics.bio-ph
Cell strain-stiffening drives cell breakout from embedded spheroids
Shabeeb Ameen, Kyungeun Kim, Ligesh Theeyancheri et al. (+5 more)
Understanding how
cells escape from embedded spheroids requires a mechanical framework linking stress generation within
cells, across
cells, and between
cells and the surrounding extracellular
matrix (ECM). We develop such a framework by coupling a 3D vertex model of a spheroid to a fibrous ECM network and deriving a 3D Cauchy stress tensor for deformable polyhedral
cells, enabling direct
cell-level stress quantification in three dimensions. We analyze maximum shear stress in solid-like and fluid-like spheroids: solid-like spheroids exhibit broader stress distributions and radial stress gradients, while fluid-like spheroids show lower stresses with weak spatial organization.
Cell shape anisotropy is not generically aligned with principal stress directions, indicating that morphology alone is an unreliable proxy for mechanical state. We further demonstrate strain stiffening at the single-
cell level, where elongation produces nonlinear increases in maximum shear stress, allowing boundary
cells in otherwise low-stress, fluid-like spheroids to transiently generate forces sufficient to remodel the
matrix. To connect strain-induced stress amplification to invasion modes, we introduce an extended 3D vertex model with explicit, tunable
cell-
cell adhesion springs. In this minimal mechanical framework, single-
cell breakout results from strain stiffening combined with reduced adhesion, whereas multi-
cell streaming additionally requires anisotropic adhesion strengthened along the elongation axis and weakened orthogonally. Together, these results identify distinct mechanical pathways coupling
cell strain, stress amplification, and adhesion organization to spheroid invasion.
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All authors Shabeeb Ameen, Kyungeun Kim, Ligesh Theeyancheri, Minh Thanh, Mingming Wu, Alison E. Patteson, J. M. Schwarz, Tao Zhang
Quantum Gases · Cross-listed from quant-ph
Non-Hermitian Renormalization Group from a Few-Body Perspective
Hiroyuki Tajima, Masaya Nakagawa, Haozhao Liang et al. (+1 more)
Non-Hermiticity plays a fundamental role in open
quantum systems and describes a wide variety of effects of interactions with environments, including
quantum measurement. However, understanding its consequences in strongly interacting systems is still elusive due to the interplay between non-perturbative strong correlations and non-Hermiticity. While the Wilsonian renormalization group (RG) method has been applied to tackle this problem, its foundation, based on the existence of the partition function, is ill-defined. In this paper, we establish a microscopic foundation of the non-Hermitian RG method from a few-body perspective. We show that the invariance of the scattering amplitude under RG transformations enables us to rigorously derive the non-Hermitian RG equation, giving a physically transparent interpretation of RG flows. We discuss a detailed structure of such RG flows in a non-relativistic two-body system with inelastic two-body loss, and show its relation to a non-Hermitian
quantum scale anomaly. Our analysis suggests that non-Hermitian complex potentials often used in high-energy physics can be interpreted as being caused by
quantum measurement, where the detection of elastically scattered particles updates the observer's knowledge, resulting in a nonunitary state change of the system. We apply our formalism to
nuclear physics, find the emergence of a critical semicircle, and show that several
nuclei are located near the critical semicircle in the coherent
neutron-
nucleus scattering. We also propose that the localized dineutron in two-
neutron halo nuclei can be interpreted as the
quantum measurement effect on the imaginary potential associated with absorption into the core
nucleus. Our result bridges different contexts of non-Hermitian systems in high-energy and atomic, molecular, and optical physics, opening an interdisciplinary playground of non-Hermitian few-body physics.
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All authors Hiroyuki Tajima, Masaya Nakagawa, Haozhao Liang, Masahito Ueda
Strongly Correlated Electrons
Frustrated spin models on two- and three-dimensional decorated lattices with high residual entropy
D. V. Dmitriev, V. Ya. Krivnov and O. A. Vasilyev
We study the ground-state properties of a family of frustrated
spin-1/2 Heisenberg models on two- and three-dimensional decorated
lattices composed of connected
star-shaped units. Each
star is built from edge-sharing triangles with an
antiferromagnetic interaction on the shared side and
ferromagnetic interactions on the others. At a critical coupling ratio, the ideal
star model - defined by equal
ferromagnetic interactions - exhibits a macroscopically degenerate ground state, which we map onto a site percolation problem on the Lieb
lattice. This mapping enables the calculation of exponential ground-state degeneracy and the corresponding residual
entropy for square, triangular, honeycomb, and cubic
lattices. Remarkably, the residual
entropy remains high for all studied
lattices, exceeding 60% of the maximal value ln(2). Despite a gapless quadratic one-
magnon spectrum, the low-temperature thermodynamics is governed by exponentially numerous gapped excitations. For a distorted-
star variant of the model, the ground-state
manifold is equivalent to that of decoupled
ferromagnetic clusters, leading to exponential degeneracy with a lower, yet still substantial, residual
entropy. At low temperature the system mimics a paramagnetic
crystal of non-interacting
spins with high
spin value ($s=4$ for a square
lattice). The obtained results establish a structural design principle for engineering
quantum magnets with a high ground-state degeneracy, suggesting promising candidates for enhanced magnetocaloric cooling and
quantum thermal machines.
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Strongly Correlated Electrons
Structural studies on $A_2$ReCl$_6$ ($A$=K, Rb, Cs): absence of Jahn-Teller distortion
A. Bertin, L. Kiefer, V. Pomjakushin et al. (+4 more)
K$_2$ReCl$_6$ belongs to the antifluorite family and exhibits a sequence of structural transitions above the onset of
magnetic order at $T_N$ = 12 K. Because of its 5d3 electronic configuration in an octahedral coordination, the ground state is a pure
spin state without orbital degeneracy within the LS coupling scheme, but it can become Jahn-Teller active in the strong
spin-orbit coupling limit described by the $jj$ coupling [S. Streltsov and D. I. Khomskii, Phys. Rev. X 10, 031043 (2020)]. While the structural transitions in K$_2$ReCl$_6$ are understood in terms of octahedral rotation and tilting, the possible impact of a Jahn-Teller distortion remains an open issue. We report on comprehensive crystalstructure studies by means of powder
neutron and single-
crystal x-ray diffraction on K$_2$ReCl$_6$ and on K$_2$SnCl$_6$. The latter material is used as a reference, because it exhibits the same sequence of structural transitions as K$_2$ReCl$_6$, but possesses a filled 4d shell ruling out a Jahn-Teller distortion. While the ReCl$_6$ octahedron in K$_2$ReCl$_6$ presents sizable distortions at intermediate temperatures, there is no such distortion persisting to low temperatures excluding a sizable Jahn-Teller effect. Studies on polycrystalline samples of Rb$_2$ReCl$_6$ and Cs$_2$ReCl$_6$, in which the structural transitions are suppressed due to the larger alkaline ionic radius, also do not find any indications for a Jahn-Teller distortion.
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All authors A. Bertin, L. Kiefer, V. Pomjakushin, O. Fabelo, P. Becker, L. Bohaty, M. Braden
Disordered Systems and Neural Networks · Cross-listed from q-bio.PE
Modeling Protein Evolution via Generative Inference From Monte Carlo Chains to Population Genetics
Leonardo Di Bari, Thierry Mora, Andrea Pagnani et al. (+3 more)
Generative models derived from large
protein sequence
alignments define complex fitness landscapes, but their utility for accurately modeling non-
equilibrium evolutionary dynamics remains unclear. In this work, we perform a rigorous comparative analysis of three simulation schemes, designed to mimic
evolution in silico by local sampling of the probability distribution defined by a generative model. We compare standard independent Markov Chain Monte Carlo, Monte Carlo on a phylogenetic tree, and a population genetics dynamics, benchmarking their outputs against deep sequencing data from four distinct in vitro
evolution experiments. We find that standard Monte Carlo fails to reproduce the correct phylogenetic structure and generates unrealistic, gradual mutational sweeps. Performing Monte Carlo on a tree inferred from data improves phylogenetic fidelity and historical accuracy. The population genetics scheme successfully captures phylogenetic correlations, mutational abundances, and selective sweeps as emergent properties, without the need to infer additional information from data. However, the latter choice come at the price of not sampling the proper generative model distribution at long times. Our findings highlight the crucial role of phylogenetic correlations and finite-population effects in shaping evolutionary trajectories on fitness landscapes. These models therefore provide powerful tools for predicting complex adaptive paths and for reliably extrapolating evolutionary dynamics beyond current experimental limitations.
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All authors Leonardo Di Bari, Thierry Mora, Andrea Pagnani, Aleksandra M. Walczak, Francesco Zamponi, Saverio Rossi
Materials Science
Phase behavior and electrical transport in DBTTF-HATCN donor-acceptor mixtures
Andreas Opitz, Hongwon Kim, Dmitry Lapkin et al. (+10 more)
The formation of donor-acceptor complexes (DACs) between the electron donor Dibenzotetrathiafulvalene (DBTTF) and the acceptor Hexaaza\-triphenylene\-hexacarbo\-nitrile (HATCN) results in a new phase with a distinctly different
crystal structure as well as new optical absorption bands below the energy gaps of the two pristine materials. X-ray scattering and atomic force microscopy provide detailed insights into the film structure and morphology by systematic variation of the mixing ratio from pristine DBTTF to pristine HATCN. The measured electrical conductivity of thin films depends in a highly non-monotonic manner on the composition of the mixture and shows significantly improved charge transport compared to the pristine films. The temperature-dependent conductivity, charge carrier concentration, and mobility were investigated across these compositions. Surprisingly, all compositions exhibited n-type behavior, except for pristine DBTTF. This behavior is explained by the electronic structure of the mixtures, as revealed by ultraviolet photoelectron spectroscopy, which indicates that charge injection and transport occur via the lowest unoccupied molecular orbital of the DAC and HATCN. Additionally, the observed electrical conductivity is strongly influenced by morphology and structural ordering of the films. These findings offer valuable insights for the design of advanced materials with enhanced electrical performance.
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All authors Andreas Opitz, Hongwon Kim, Dmitry Lapkin, Gianfranco Melis, Ainur Abukaev, Marie Siegert, Lennart Frohloff, Lisa Schraut-May, Oleg Konovalov, Alexander Hinderhofer, Frank Schreiber, Jens Pflaum, Wolfgang Brütting
Mesoscale and Nanoscale Physics
First-principles discovery of stable, anisotropic, semiconducting Sb2X2O (X = S, Se) and Janus Sb2SSeO nanosheets for optoelectronics and photocatalysis
Masoud Shahrokhi and Bohayra Mortazavi
In this work, we conduct a comprehensive first-principles investigation into the design and discovery of novel antimony oxychalcogenide monolayers Sb2X2O (X = S, Se) and Janus Sb2SSeO, examining their structural stability, elastic, electronic, optoelectronic, and photocatalytic properties. Our analysis confirms their thermodynamic and dynamical stability and reveals low cleavage energies, indicating strong feasibility for mechanical exfoliation. The excellent agreement between our HSE06-predicted bandgap of bulk Sb2S2O and experimental measurements further validates the employed computational framework. EWe also find that their optoelectronic responses can be efficiently tuned via biaxial strain, providing a viable route for device-specific property engineering. Favorable band
alignments, strong optical absorption, efficient carrier transport, and relatively high dielectric constants collectively support their candidacy for overall water splitting under neutral conditions.These results establish a solid theoretical foundation for the rational design of Sb-based 2D nanostructures and highlight their potential in next-generation direction-dependent optoelectronic and sustainable energy-conversion applications.
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Mesoscale and Nanoscale Physics
Elastic field causing noncommutativity
A. L. Silva Netto, A. M. de M. Carvalho, G. Q. Garcia et al. (+1 more)
We study how a uniform torsion background, modeling a continuous density of screw dislocations and induces effective spatial noncommutativity and reshapes the energy spectrum of a free
quantum particle. Within the
geometric theory of defects, the metric yields a first-order (
magnetic-like) coupling in the transverse dynamics, equivalent to an effective
magnetic field $B_{eff}$ proportional to $p_z Omega$, where $Omega$ encodes the torsion strength. In the strong-coupling (Landau) regime, the planar coordinates obey [x,y] != 0 and the spectrum organizes into Landau-like levels with a slight electric-field-driven tilt and a uniform shift. Thus, increasing $Omega$ drives the system continuously toward the familiar Landau problem in flat space, with torsion setting the noncommutativity scale and controlling the approach to the Landau limit.
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All authors A. L. Silva Netto, A. M. de M. Carvalho, G. Q. Garcia, C. Furtado
Mesoscale and Nanoscale Physics
Magnon confinement and trapping at the nanoscale
J. Chen, H. Yu, R. Gallardo et al. (+2 more)
Magnon confinement and trapping refer to the localization of
magnons-quasiparticles that represent collective
spin-wave excitations in
magnetic materials-within specific regions or structures. This concept is essential in magnonics, a subfield of spintronics that leverages
spin waves for processing and transmitting information. Compared to conventional electronics, magnonics offers lower power consumption and faster operation, making it a promising technology for future devices.
Magnons can be confined using both static and dynamic methods, often relying on potential wells and barriers to restrict their free propagation and trap them in designated locations. In this review, we will explore the main strategies for
magnon confinement and trapping, including:
magnetic field inhomogeneities,
spin textures (i.e. domain walls,
vortices, skyrmions) nanostructured materials (i.e. nanowires, disks, and magnonic
crystals), topological states,
chiral magnons and flat band formation, induced by dipole-dipole interactions and Dzyaloshinskii-Moriya interaction. Microwave cavities and resonant
magnetic fields, as well as
spin-torque effects and Bose-Einstein condensation contribute to
magnon localization. Furthermore,
spin-wave edge and cavity modes have been observed in two-dimensional
magnetic materials and twisted moiré superlattices at a specific twist angle.
Magnon trapping has broad applications in computing and data processing, particularly in the development of magnonic
crystals, waveguides, and
memory elements. Additionally,
magnon systems are being explored for
quantum computing, where confinement can enhance the coupling between
magnons and other quasiparticles in hybrid
quantum systems. Precision control of
magnons could lead to next-generation spintronic devices, offering improved efficiency and scalability.
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All authors J. Chen, H. Yu, R. Gallardo, P. Landeros, G. Gubbiotti