Materials Science · Cross-listed from cs.LG
UNATE: UNsupervised ATomic Embedding for crystal structures property prediction
Laura Solà-Garcia, Àlex Solé and Javier Ruiz-Hidalgo
Accurately predicting
crystal properties is critical for accelerating materials discovery, but it is often limited by scarce labeled data and costly theoretical calculations. To alleviate this, we propose UNATE (Unsupervised Atomic
Embedding), a framework that leverages structural information extracted from unlabeled
crystal structures. UNATE integrates an unsupervised denoising autoencoder with self-supervised contrastive learning to learn robust atomic representations, which are then used as input features for downstream property prediction. Experimental results show that replacing raw atomic numbers with UNATE-pretrained node
embeddings yields a 2.7% improvement over the full-data baseline. Notably, the benefits become more pronounced in scenarios with limited labeled data, reaching improvements of up to 10% when only 25% of the labeled data is used.
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Mesoscale and Nanoscale Physics
Hybridization of Ferromagnetic and Cyclotron Resonances in a Two-Dimensional Electron System on a Ferromagnetic Film
A. A. Zabolotnykh, I. V. Zagorodnev, A. A. Matveev et al. (+5 more)
The microwave response of a two-dimensional (2D) electron system located on a dielectric
ferromagnetic film, which in turn lies on a conducting metal (gate), has been theoretically studied. The entire system has been placed in the perpendicular static
magnetic field. It has been found that the
ferromagnetic resonance of the film and the cyclotron resonance of the electrons of the 2D system interact in the
magnetic field, leading to their repulsion ('anticrossing'). It has been revealed that the anticrossing region is characterized not only by the modification of resonance frequencies compared to the cyclotron resonance in the 2D system without the
ferromagnetic substrate and the
ferromagnetic resonance in the film without the 2D system, but also by a strong change in the resonance linewidths.
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All authors A. A. Zabolotnykh, I. V. Zagorodnev, A. A. Matveev, D. A. Rodionov, O. Yu. Arkhipova, D. V. Kalyabin, A. R. Safin, S. A. Nikitov
Materials Science
Dealloying by peritectic melting
Mingwang Zhong and Alain Karma
Peritectic melting of Ti–Ag has been shown experimentally to form bicontinuous structures, but the mechanism remains unclear. Here we use phase-field simulations to show that these structures arise from a morphological instability of
liquid film migration in three dimensions: a Ti-rich solid growing through an Ag-rich
liquid film develops a branched seaweed or dendritic structure whose side branches coalesce to form handles, generating a high-genus bicontinuous
topology. A sharp-interface theory predicts a solidification-front velocity and an initial ligament width that are constant in time, in contrast to
liquid metal dealloying; subsequent $t^{1/3}$ coarsening reproduces the experimentally observed final ligament width.
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Superconductivity · Cross-listed from quant-ph
Sideband fingerprints of antibunched light in cascaded quantum wave mixing
R. D. Ivanovskikh, W. V. Pogosov, A. A. Elistratov et al. (+5 more)
Quantum wave mixing on a single superconducting
qubit produces a hierarchy of coherent side peaks associated with elastic multiphoton scattering pathways. In a cascaded source–probe geometry these pathways become sensitive to the
photon statistics of the radiation emitted by the source
qubit. We develop an analytical theory of this effect starting from the cascaded master equation in the weak-driving regime. In the coherent-filtering limit when the decay rate of the probe
qubit is less than that of the source, the standard coherent–coherent wave-mixing hierarchy is recovered. In the opposite limit, side peaks associated with multiphoton absorption from the antibunched source field are parametrically suppressed. Numerical solutions confirm the analytical scaling laws. The resulting sideband hierarchy provides a frequency-domain fingerprint of antibunched itinerant microwave light.
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All authors R. D. Ivanovskikh, W. V. Pogosov, A. A. Elistratov, A. Yu. Dmitriev, T. R. Sabirov, A. V. Vasenin, S. A. Gunin, O. V. Astafiev
Statistical Mechanics
Equivalent-neighbor $k$-core percolation in two dimensions
Qiyuan Shi, Ming Li and Youjin Deng
We perform large-scale numerical simulations to investigate the critical behavior of $k$-core percolation in two dimensions with an extended interaction range $r$. By systematically varying both the core index $k$ and the interaction range $r$, we construct a comprehensive phase diagram in the $(k,r)$ plane. In contrast to $k$-core percolation in infinite dimensions, no hybrid transition is observed in two dimensions: the phase diagram contains only a continuous transition regime and a strictly first-order regime, separated by a tricritical or critical-end point $(k_s,r_s)$. For $k<k_s$ and $r<r_s$, the transition is continuous and belongs to the universality class of standard two-dimensional (2D) percolation. For $k>k_s$ and finite $r>r_s$, the transition is discontinuous, with no hybrid features or critical singularities. In this first-order regime, the pseudocritical point approaches the critical point as $1/\ln L$, where $L$ is the linear system size, distinct from the $L^{-d}$ scaling typical of conventional thermodynamic first-order transitions in $d$ dimensions. This logarithmic finite-size drift is consistent with a nucleation-driven mechanism, in which rare voids trigger the collapse of the finite-range $k$-core. These results demonstrate that
geometric constraints can fundamentally alter the nature of $k$-core percolation found in finite dimensions.
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Mesoscale and Nanoscale Physics
Topological fragility and bilinear magnetoelectric resistance in gapless edge states
Cosimo Gorini, Matthieu Bard, Sophie Gueron et al. (+2 more)
In time-reversal symmetric systems such as topological and higher-order topological
insulators, 1D
spin-momentum locked edge and hinge states are theoretically “perfectly conducting”, being immune to backscattering by non-
magnetic disorder. Here, we reveal a fundamental “topological fragility”: these states exhibit a bilinear magnetoelectric resistance significantly larger than in 2D systems. This effect requires two ingredients: (i)
spin-momentum locking, which maximizes time-reversal
symmetry breaking in the non-linear regime, and (ii) random
spin-orbit interaction – the same mechanism behind Elliott - Yafet
spin relaxation in heavy elements. Together, these generate a robust backscattering channel when a modest external
magnetic field is applied. Our theory requires no gap opening or complex many-body effects, offering a simple and general mechanism that quantitatively explains recent observations in Bismuth hinge states.
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All authors Cosimo Gorini, Matthieu Bard, Sophie Gueron, Hélène Bouchiat, Giovanni Vignale
Soft Condensed Matter
Collective deformation of anisotropic particles with internal pulsation
Luca Casagrande, Alessandro Manacorda and Étienne Fodor
Capturing the emergence of deformation waves in contractile living tissues is a challenge that has recently been tackled with models of actively deformable particles. Inspired by the anisotropic deformation of cardiomyocytes in cardiac tissues, we examine how the pulsation of elliptical particles affects their collective properties in dense assemblies. We introduce two types of deformation where the eccentricity of each particle is subject to a periodic drive, and examine the interplay between nematic order and synchronized deformation via a systematic phase diagram. We derive a hydrodynamic description through a coarse-graining procedure, and show that it qualitatively captures the main collective states of the microscopic dynamics. Overall, our model provides key insights into how an active anisotropic deformation yields waves that self-organize into various dynamical patterns.
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Disordered Systems and Neural Networks
Spectral properties of non-Hermitian real random matrices with long-range correlations
Ulysse Marquis
We investigate the spectral properties of non-Hermitian real random
matrices whose entries exhibit long-range correlations decaying as~$|r-r'|^{-\alpha}$. We find a progressive breakdown of the circular law, controlled by the decrease of~$\alpha$. In all cases, the radial
eigenvalue density decreases away from the origin. At~$\alpha>1$, an effective radius, reminiscent of the circular law, is retrieved, while instead, for~$\alpha<1$, the
eigenvalue distribution broadens with
matrix size and its spectral radius grows like a power law, with exponents numerically close to the exponents controlling the magnitude of fluctuations in the extended central limit
theorem. The case~$\alpha=1$ appears as a case with self-similar
eigenvalue density, and slowly growing spectral radius. Long-range correlations also enhance clustering of real
eigenvalues and slow the resorption of the Saturn effect. These results reveal a correlation-driven transition and suggest the emergence of a new universality class for correlated non-Hermitian random
matrices.
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Soft Condensed Matter
The Remodeling of Fiber Distributions in Biological Tissues: Rotation without Rotation
Christian Cherubini, Marcello Vasta, Filippo Recrosi et al. (+1 more)
Collagen remodeling in living tissues exhibits anisotropic orientation patterns commonly described by Von Mises distributions, yet the physical origin of such nonequilibrium organization remains unresolved. In the present work, we demonstrate analytically that the combined action of Malthusian growth dynamics and the introduction of linear relations governing mechanical remodeling naturally gives rise to generalized bimodal Von Mises distributions as emergent states of living matter. The theory reveals a rotation without rotation mechanism, in which fibers progressively reorient in the absence of angular mechanical coupling via selective deposition and removal along preferred directions. The resulting analytical solutions quantitatively reproduce experimentally observed distributions and establish a direct mechanobiological origin for directional statistics in biological tissues. By interpreting the evolving normalized fiber density as a probability distribution function, we formulate a dynamical Shannon
entropy framework that captures the temporal emergence of microstructural organization. The theory further yields closed-form expressions for the drift of the associated Fokker–Planck equation, enabling the corresponding
stochastic differential equation to be derived, thus revealing that tissue remodeling is the collective outcome of noisy single-fiber dynamics. These results establish a minimal theoretical framework that connects biomechanics,
stochastic processes, and nonequilibrium statistical organization in living matter.
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All authors Christian Cherubini, Marcello Vasta, Filippo Recrosi, Alessio Gizzi
Materials Science
kikuchipy: an open-source toolbox for analysis of EBSD patterns
Håkon W. Ånes, Phillip Crout, Lars Andreas Lervik et al. (+5 more)
We present kikuchipy, an open-source toolbox for analysis of electron backscatter diffraction patterns, written in Python. The software is capable of both Hough and dictionary indexing and orientation and/or projection center refinement of patterns stored in file formats from all major vendors. Indexing results can be validated using maps independent of indexing and by visually comparing experimental and simulated patterns. By leveraging scientific packages in the Python ecosystem, emphasis is put on making the indexing workflow flexible and improve results through fast iteration. The software's capabilities are demonstrated on three application examples: analysis of orientation relationships in a super duplex stainless steel, phase differentiation of aluminium and silicon in a cast modified Al-Si
alloy, and phase differentiation of particles in an Al-Mn
alloy as Al6Mn or alpha-AlMnSi. The diffraction patterns and analysis workflows are made publicly available. kikuchipy was created and is developed as a resource for the electron microscopy community, allowing anyone to improve the software or include it into their own analysis workflows or softwares.
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All authors Håkon W. Ånes, Phillip Crout, Lars Andreas Lervik, Ole Natlandsmyr, Tina Bergh, Jarle Hjelen, Antonius T. J. van Helvoort, Knut Marthinsen
Materials Science
Alignment-free ultra-broadband parametric frequency conversion in lead-halide perovskites
Abhishek Shiva Kumar, Dusan Lorenc, Ayan A. Zhumekenov et al. (+2 more)
Lead-halide perovskites were demonstrated to exhibit some of the largest known optical nonlinearities, yet their potential for frequency conversion remains largely untapped. Here we demonstrate ultra-broadband four-wave mixing of near- and mid-infrared femtosecond pulses in thick single-
crystal LHPs, generating bright, coherent, and highly collimated emission across an exceptionally wide continuous tuning range without phase-matching engineering, angular
alignment, or dispersion optimization. Time resolved measurements reveal that the emission originates near the
crystal surfaces, where phase-matching constraints are relaxed, while the unusually large intrinsic $\chi^{(3)}$ response preserves efficient and directional frequency conversion despite the strongly localized interaction volume. These results position LHPs as a powerful bulk platform for ultra-broadband nonlinear photonics, opening a pathway toward compact,
alignment-free architectures for ultrafast frequency conversion.
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All authors Abhishek Shiva Kumar, Dusan Lorenc, Ayan A. Zhumekenov, Osman M. Bakr, Zhanybek Alpichshev
Soft Condensed Matter
Chain conformations in adsorbed layer during polymer capillary imbibition
Tao Liang, Li Peng, Xianbo Huang et al. (+1 more)
We conducted molecular dynamics simulations to investigate chain conformations in adsorbed layers during
polymer capillary imbibition. While the imbibition length adheres to the classical Lucas-Washburn equation, a notable deviation in mobile bead density emerges under strong confinement, consistent with in situ dielectric spectroscopy experiments. The proportion of loop structures within adsorbed layers progressively increases during capillary infiltration, attributed to the relaxation of initially stretched chains toward
equilibrium configurations. Furthermore, systematic analysis revealed that chain relaxation dynamics exhibit length-dependent retardation, especially under high confinement. The characteristic desorption time demonstrates chain-length dependence in quantitative agreement with scaling predictions.
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All authors Tao Liang, Li Peng, Xianbo Huang, Jiajia Zhou
Materials Science · Cross-listed from physics.chem-ph
Machine Learning Multiscale Interactions
Àlex Solé, Sergio Suárez-Dou, Albert Mosella-Montoro et al. (+4 more)
Realistic physical systems are characterised by emergent interactions across multiple length and time scales, posing a significant challenge for predictive machine learning (ML) models. Most scientific ML models focus on a narrow range of interactions. While machine learning force fields (MLFFs) offer near-
quantum accuracy, the ubiquitous message-passing layers miss long-range many-body effects. Here we introduce the Multiscale Structural Ensemble (MuSE), a hierarchical model that uses Soft Coarse-Graining Pooling to construct coarse representations from smooth fractional assignments of atoms to coarse nodes, enabling MLFF modules to operate across multiple scales. MuSE is architecture-agnostic and coupled with SO3krates, MACE, and PaiNN MLFFs for both molecules and materials. We demonstrate the power of MuSE through Hessian-based
benchmarks, folding trajectories for biomolecules, and energy profiles in molecule-
graphene nanostructures, where MuSE accurately captures
quantum-mechanical interactions at relevant scales – unlike other recent long-range ML models.
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All authors Àlex Solé, Sergio Suárez-Dou, Albert Mosella-Montoro, Silvia Gómez-Coca, Eliseo Ruiz, Alexandre Tkatchenko, Javier Ruiz-Hidalgo
Materials Science · Cross-listed from physics.plasm-ph
Pulse magnet of 10 T for power laser experiments with x-ray free-electron laser diagnostics
Akihiko Ikeda, Kosuke Noda, Yutaro Yamanaka et al. (+22 more)
The importance of investigating magnetized
plasmas/solids in extreme conditions has grown over the last decades, particularly in the field of high energy density physics (HEDP), such as laboratory astrophysics and inertial confinement fusion. However, up to now, the unique capabilities of an X-ray free-electron
laser (XFEL), such as high brilliance and low divergence have never been exploited for this type of research. In this paper, we present the first platform developed at SACLA, Japan, that combines a high-power optical
laser for generating matter under extreme conditions of pressure and temperature, an XFEL probe, and an external
magnetic field. The high current is produced using a 2 kV, 4.8 kJ pulsed power system giving a maximum current of 10 kA which is synchronized with the optical
laser and XFEL in a
vacuum environment. It flows through a split-pair coil to generate a high
magnetic field (10 T at 6 kA) which has 1 cm access every 45$^{\circ}$ in the equatorial plane and 90$^{\circ}$ in the poloidal one. This platform offers new opportunities to study high-energy-density matter in strong
magnetic fields, including shock propagation, instability growth, and turbulent
plasma dynamics.
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All authors Akihiko Ikeda, Kosuke Noda, Yutaro Yamanaka, Yuma Urabe, Keiichiro Kawai, Yasuhiro H. Matsuda, Hirotaka Nakamura, Ryusuke Yamamoto, Yoshiki Naito, Yasuhiro Kuramitsu, Kai Taketoshi, Naoki Yamagata, Norimasa Ozaki, Tatiana Pikuz, Yoichi Sakawa, Takayoshi Sano, Ryosuke Kodama, Taichi Morita, Tomoya Ogawa, Kohei Miyanishi, Toshinori Yabuuchi, Rigon Gabriel, Bakandreas Stavros, Koenig Michel, Bruno Albertazzi
Strongly Correlated Electrons
Near-Room-Temperature Antiferromagnetic Ordering in the Quadruple Perovskite Sr4NaRu3O12
Subham Naik, Biswajit Singh, Hiranmayee Senapati et al. (+10 more)
We report the synthesis, structure and
magnetic properties of two 1:3 ordered quadruple perovskites Sr4MRu3O12 (M = Li and Na). Sr4NaRu3O12 crystallizes in the centrosymmetric space group R-3 and Sr4LiRu3O12 appears to be isostructural to the Na compound based on the PXRD data. In Sr4NaRu3O12, both Na and Ru are predominantly ordered at the B sites (here Na/Li and Ru) and the structure contains only corner-connected RuO6 and NaO6 octahedra. This atomic ordering also leads to a rather large unit
cell with a = 11.25 Å and c = 27.6 Å compared to the basic 12R structure (a = 5.5 Å and c ~ 27 Å).
Magnetic measurements reveal that Sr4NaRu3O12 undergoes a
magnetic transition to an
antiferromagnetic state below TN ~ 265 K which is confirmed by DSC and
neutron diffraction. The Ru moments show a collinear
antiferromagnetic spin alignment along the hexagonal c axis with a propagation vector k = (0, 0, 1.5). Interestingly, those Ru moments lying on the three-fold roto-inversion do not significantly contribute to the
magnetic order, since they are located between antiferromagnetically coupled Ru atoms and are therefore probably highly frustrated. Band structure calculations on Sr4NaRu3O12 complement the observed
magnetic ground state and a semiconducting behavior in the compound. Sr4LiRu3O12 shows a
magnetic anomaly below 110 K, possibly associated with competing
ferromagnetic and
antiferromagnetic interactions.
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All authors Subham Naik, Biswajit Singh, Hiranmayee Senapati, Akshay K. U., Ramesh C. Nath, Soumyojit Chatterjee, Rahul Sharma, Thomas Doert, Walter Schnelle, Manfred Reehuis, Thomas C. Hansen, Michael Ruck, Gohil S. Thakur
Statistical Mechanics
Analysis of Critical Points in a Permutation Model on Hierarchical Lattices by Real-Space Renormalization Group
Ryuki Ito, Taisei Matsuo and Masayuki Ohzeki
The permutation model is a classical
spin system where elements of the symmetric group interact with one another. The partition function of this model is directly related to the
entanglement structure of random
quantum circuits and random tensor networks. In these contexts, the
entanglement entropy undergoes a transition between area-law and volume-law scaling, depending on the model parameters. This transition point has attracted considerable
attention. In the present work, we investigate the
ferromagnetic-paramagnetic phase transition of the permutation model, which corresponds to the
entanglement entropy transition. Using exact real-space renormalization group calculations on self-dual hierarchical
lattices, we numerically determine finite-replica critical points for (q=mn=2,...,6). We compare the results with the duality prediction based on the
Fourier transform of the symmetric group and then extrapolate the b=3 data toward the replica limit $mn\to0$, where the effective dimension is two. The comparison supports the duality-based estimate while also clarifying the systematic uncertainty associated with the extrapolation formula.
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Strongly Correlated Electrons
The evolution of pairing correlation with $3d_{z^{2}}$ electron filling in a bilayer two-orbital model for La$_3$Ni$_2$O$_7$
Y. F. Chen, Y. Shen, X. J. Qian et al. (+2 more)
The discovery of high-${T_c}$ superconductivity in pressurized
bilayer nickelate La$_3$Ni$_2$O$_7$ presents a new arena for exploring unconventional pairing mechanisms. A pivotal yet unresolved issue is the specific role of the $3d_{z^{2}}$ orbital of Ni. While its inter-layer super-exchange
antiferromagnetic coupling is widely considered crucial for superconductivity, the role of its itinerancy remains undetermined. Early studies showed that the superconductivity is accompanied by the emergence of a small
Fermi pocket of the $3d_{z^{2}}$ orbitals. However, recent experiments show controversial results on the role of the $3d_{z^{2}}$
Fermi pocket on superconductivity. Motivated by these experimental results, we investigate an effective
bilayer two-orbital model for La$_3$Ni$_2$O$_7$ using density-
matrix renormalization group (DMRG) on a minimal one-dimensional geometry. By systematically varying the $3d_{z^{2}}$ orbital filling from $1/12$ doping to half-filling, we observe a pronounced suppression of superconducting correlations near half-filling. Our results demonstrate the itinerancy of $3d_{z^{2}}$ orbital is favorable for the pairing in the
bilayer two-orbital model for La$_3$Ni$_2$O$_7$. Moreover, we observe that the pairing correlation is enhanced in regions where charge fluctuations are large, suggesting a competition between charge order and superconductivity in the model.
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All authors Y. F. Chen, Y. Shen, X. J. Qian, G. M. Zhang, M. P. Qin
Strongly Correlated Electrons
On the Relation Between String Order Parameters, Entanglement, and Dynamical Quantum Phase Transitions in Topological Dynamics
Sirshendu Bhattacharyya, Szczepan Głodzik and Nicholas Sedlmayr
Topological order is defined by topological invariants, rather than
symmetries and local order parameters. Nonetheless some topological phases can be characterized by string order parameters and
entanglement. In this article we study how string order parameters and
entanglement spectra behave out-of-
equilibrium following quenches in one dimensional topological models with $\mathbb{Z}$ invariants. Previously it has been suggested that string order parameters could serve as an experimental probe of dynamical
quantum phase transitions. Despite the existence of clear zeroes in the order parameters at critical times, we show that in general there is no exact quantitative or qualitative connection with the critical times of dynamical
quantum phase transitions. Another possible connection is of dynamical string order parameter zeroes and dynamical crossings at the center of
entanglement spectra. Here we see that there can sometimes be a connection, but it is not typical. Again there is no general quantitative or qualitative connection. Each dynamical form of criticality behaves independently, though we do see that critical times tend to be of the same order of magnitude and give an argument for why this is the case. We also find that a string order parameter which labels one topological phase can undergo non-trivial dynamics even following a quench between other topological phases. We elucidate where connections can be made, and where they result from a consideration of insufficiently general models. These results cast doubt on the idea of genuine dynamical phases following quenches in such models.
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Statistical Mechanics · Cross-listed from q-bio.NC
Balancing structure and randomness: maximum entropy networks for context-dependent computations
Ludwig Hruza and Srdjan Ostojic
Understanding how network function constrains neural connectivity is a central challenge in neuroscience. An influential approach is to train neural networks with gradient descent on cognitive tasks and characterize the resulting connectivity. A key limitation is that the resulting structure depends on the details of the training procedure. Here we propose a complementary normative approach based on the maximum
entropy principle for network connectivity, independent of any particular learning
algorithm. We describe connectivity as a probability distribution over single-
neuron weights, express task requirements as constraints on this distribution, and determine the unique distribution maximizing Shannon
entropy subject to these constraints. A weight scale parameter controls the balance between randomness and task-induced structure. We apply this framework to context-dependent input-selection tasks in 2-layer feed-forward networks, and show that maximum
entropy inference becomes analytically tractable by mapping nonlinear networks onto gain-modulated linear models. Starting from an a priori homogeneous distribution, we find that maximizing
entropy under task constraints leads to the emergence of populations of
neurons, each defined by its pattern of contextual gain modulation. Increasing the number of contexts drives a transition from context-specialized to unspecialized, random populations. Increasing the weight scale drives a parallel transition from structured to random stimulus selectivity. Strikingly, this maximum
entropy connectivity matches both qualitatively and quantitatively the structure of networks trained with gradient descent across different learning regimes. Our results suggest that the interplay between task constraints and
entropy maximization provides a fundamental principle for understanding the relationship between structure and function in neural networks.
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Soft Condensed Matter
A sweeping twist defect as a topological flagellum that drives colloid motion
Qi Xing Zhang, Claire Dore, Mojtaba Rajabi et al. (+2 more)
Nematic
liquid crystals can dramatically reconfigure under dynamic forcing, providing exciting opportunities in active matter. Here, we study a hybrid disk colloid rotated by an external field which generates a dynamic companion topological defect. The disk moves faster when the defect sweeps across the disk's face. We identify the defect as a non-singular twist wall, characterize the twist energy landscape, and identify the sweeping motion as a topological instability. As the defect sweeps, it reverses the handedness of twist and lowers the free energy in the fluid in the gap above the disk. Landau-de Gennes modeling shows that the sweeping wall behaves as a propagating director texture: the director field is nearly stationary in the wall frame, while nematogens rotate locally as the wall passes. The nematogens' rotation generates a viscous stress on the surface of the disk that hastens its propulsion. Thus, the defect acts as a flagellum that powers colloid swimming, providing an example of a dissipative topological structure whose dynamics can be harnessed to perform useful work.
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All authors Qi Xing Zhang, Claire Dore, Mojtaba Rajabi, Edward B. Steager, Kathleen J. Stebe
Superconductivity · Cross-listed from astro-ph.HE
Superfluid fraction and effective ion mass in the crystalline crust of a neutron star: role of interband response
Nicolas Chamel
Neutron superfluidity in the inner crust of a
neutron star is further investigated, focusing on the role of the interband response in the superfluid fraction and the effective mass of crustal ions induced by their motion through the superfluid. Calculations are performed within the linear response theory of the self-consistent time-dependent Hartree-Fock-Bogoliubov equations with Skyrme
nuclear energy density functionals in the Bardeen-Cooper-Schrieffer approximation. The absence of interband response in previous analyses is clarified. The
neutron superfluid density is formally shown to be consistent with the entrainment
matrix derived earlier in homogeneous
neutron-
proton superfluid mixture, thus providing a unified description of entrainment effects in the inner crust and outer core of a
neutron star within the same microscopic framework. The relative importance of the intraband and interband responses in different regions of the crust is numerically assessed from three-dimensional band-structure calculations, taking into account
quantum zero-point motion of ions about their
equilibrium position. The
neutron superfluid fraction is found to be enhanced by the interband response, resulting in effective ion masses that remain close to the mass of
quantum mechanically bound nucleons for realistic
neutron pairing gaps. Results are compared to predictions from classical hydrodynamics with different prescriptions for the permeability of ions to superfluidity.
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Superconductivity
Nitrogen-doped W0.75Re0.25 Superconducting Nanowire Single Photon Detectors
F. Colangelo, Abhishek Kumar, H. Wang et al. (+4 more)
Nitrogen-doped Tungsten-Rhenium superconducting
alloys were recently proposed as a promising material platform for superconducting nanowire single-
photon detectors (SNSPDs), offering a favorable balance between high normal state resistivity and tunable superconducting properties. In this work, we report on the fabrication and characterization of SNSPDs based on thin W0.75Re0.25 films deposited by reactive DC magnetron sputtering in a mixed Ar/N2 atmosphere. Meander detectors with 70 nm linewidth exhibit saturated internal detection efficiency (IDE) up to 1310 nm and 85.3% IDE at 1550 nm at 2.5 K, with sub-nanosecond rise times, decay times of the order of a few nanoseconds, and timing jitter of 73.2 ps measured with room temperature amplifiers.
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All authors F. Colangelo, Abhishek Kumar, H. Wang, F. Avitabile, C. Attanasio, I. Esmaeil Zadeh, C. Cirillo
Disordered Systems and Neural Networks
Sensitivity to perturbations in the three-dimensional Anderson model
Piotr Tokarczyk, Lev Vidmar, Anatoli Polkovnikov et al. (+1 more)
We investigate the fidelity susceptibility, which quantifies the sensitivity of single-particle eigenstates to perturbations, in the three-dimensional Anderson model. As a function of disorder strength $W$, it exhibits two distinct peaks. The first peak signals a crossover at weak disorder strength from plane-wave states to single-particle
quantum chaos, and its position shifts toward $W\to 0$ in the thermodynamic limit. The second peak emerges, to high numerical accuracy, at the critical disorder strength associated with the Anderson localization transition. We further show that the divergence of the first peak is maximal, scaling as the square of the inverse frequency cutoff, whereas the divergence of the second peak is submaximal. We relate the latter suppression to the fractal structure of single-particle eigenstates at criticality. We discuss two distinct scenarios that give rise to the peaks in the fidelity susceptibilities. Moreover, studying the scaling of typical fidelity susceptibilities above the Anderson transition, we find evidence of two distinct regimes of nonergodic behavior.
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All authors Piotr Tokarczyk, Lev Vidmar, Anatoli Polkovnikov, Patrycja Łydżba
Strongly Correlated Electrons
Magnetoelastic effects in the metallic frustrated antiferromagnet CrB$_2$
Tadataka Watanabe, Mai Watanabe, Sakurako Suganuma et al. (+2 more)
Hexagonal chromium diboride CrB$_2$ is a metallic frustrated antiferromagnet with a Néel temperature $T_N \sim$ 88 K. In CrB$_2$, Cr 3$d$ electrons not only give rise to localized
magnetic moments but also contribute to metallic conduction. We perform ultrasound velocity measurements on a single
crystal of hexagonal CrB$_2$ to determine its elastic properties. The temperature dependence of the $ab$-plane shear elastic modulus exhibits Curie-type softening upon cooling from $\sim$120 K down to $T_N$. This behavior is interpreted as a precursor to a
symmetry-lowering
lattice distortion at $T_N$, indicating that
magnetic frustration is relieved via transverse magnetoelastic coupling. In addition, the $a$-axis and $c$-axis compressive elastic
moduli show unusual softness and their suppression upon cooling, which are naturally explained by
Fermi-surface nesting and its suppression upon cooling. The present results suggest that, in CrB$_2$, longitudinal magnetoelastic coupling suppresses
Fermi-surface nesting and enhances frustrated exchange interactions, while transverse magnetoelastic coupling plays a key role in relieving the frustration.
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All authors Tadataka Watanabe, Mai Watanabe, Sakurako Suganuma, Andreas Bauer, Christian Pfleiderer
Materials Science
Transition from Homogeneous to Domain-Wall-Mediated Polarization Switching in BaTiO3: A Machine-Learning Molecular Dynamics Study
Po-Yen Chen and Teruyasu Mizoguchi
Polarization switching in ferroelectric BaTiO3 can proceed through fundamentally different mechanisms - yet the conditions that determine which pathway is realized remain poorly understood. Using machine-learning potential-based molecular dynamics with the MACEField model, we systematically vary supercell size to reveal a clear transition from homogeneous polarization switching to domain-wall (DW)-mediated switching, accompanied by a coercive field increase of over 50%. Shannon
entropy analysis demonstrates that this transition is driven by size-dependent polarization fluctuations that promote 180 degree DW nucleation - establishing a direct, quantitative link between local configurational disorder and macroscopic switching behavior. Additional analyses further suggest that the switching pathway is also influenced by the kinetic competition between DW nucleation/growth and annihilation. Furthermore, the switching pathway and hysteresis response are shown to depend critically on supercell geometry and the relative orientation of applied stress and electric field. These findings reveal that homogeneous and DW-mediated switching are distinct physical regimes in BaTiO3, and that atomistic simulations must account for system size to correctly capture the operative switching mechanism.
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Materials Science
Spin layer groups and their corepresentations
Zeying Zhang, Gui-Bin Liu, Mu Tian et al. (+3 more)
Spin layer groups are the crystallographic
symmetry groups with a periodic plane, and their
symmetry operations are inherited from three-dimensional (3D)
spin space groups. However, the direct application of 3D
symmetry groups to two-dimensional systems is often inadequate due to anisotropic axes and dimensional reduction. In this work, we systematically classify inequivalent
spin layer groups and analytically derive their irreducible corepresentations. This classification establishes a foundational framework for investigating
symmetry-protected properties and novel
quantum states in low-dimensional
magnetic materials.
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All authors Zeying Zhang, Gui-Bin Liu, Mu Tian, Run-Wu Zhang, Zhi-Ming Yu, Yugui Yao
Mesoscale and Nanoscale Physics
AI-Driven SERS for Non-invasive and Label-Free Extracellular Vesicle Detection Across Cellular Origins in Tears and Sweat
Yang Li, Xiaoming Lyu, Ling Xia et al. (+5 more)
Wearable sensing technology capable of point-of-care, continuous and non-invasive analysis of exosomes in biofluid such as tears and sweat is an essential part for future personalized medicine. Major detection and identification methods of
cell secreted Extracellular Vesicles (EVs) often require labeling and are time-consuming, resulting in low efficiency in EV mechanism research and disease diagnosis. While the label-free Surface-enhanced Raman spectroscopy (SERS) has been combined with deep learning model for EV identification in blood, their application to non-invasive detection of EVs in tears and sweat are missing. Here, we filled this gap by developing an artificial intelligence (AI)-assisted Surface-enhanced Raman spectroscopy (SERS) method based on salt-induced nanoparticle aggregation for fast EV identification in tears and sweat with high accuracy. Significantly, our label-free detection and AI differentiation of EVs from 6
cell lines (HepG2, Hela, 143B, LO-2, BMSC, H8) achieved the identification of EVs in tear fluids from 7 different disease sources with accuracies >92%. Our results showed that this platform can not only distinguish EVs from multiple
cell sources but also generate highly reproducible and selective EV signals in tear fluids without a need for chemical labeling or separation steps. Molecular dynamics simulations revealed that silver atoms (Ag) form electrostatic interactions with oxygen atoms of multiple amino acid residues in
proteins, suggesting a high affinity. This strategy realizes ultra-sensitive and anti-interference detection of EVs, providing a new idea for the rapid diagnosis of clinical diseases.
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All authors Yang Li, Xiaoming Lyu, Ling Xia, Kuo Zhan, Haoyu Ji, Lei Qin, Seppo J. Vainio, Jian-An Huang
Soft Condensed Matter
Non-equilibrium pathway to mesoscale ordering in ethanol-water binary liquid
Xinyue Jiang, Yating Shang, Jianhui Li et al. (+3 more)
Ethanol-water mixtures are a classic example of thermodynamic non-ideality, yet the structural origin of their pronounced anomalies, such as volume contraction and a large negative excess
entropy, has remained a long-standing puzzle. Here, we demonstrate these anomalies are not
equilibrium properties but calorimetric fingerprint of an arrested phase transition. By imposing periodic thermal oscillations, we drive a 50% (v/v) ethanol-water system along a complete hierarchical self-assembly pathway that progressed from ethanol clusters to water-containing droplets, then to acicular flakes, and finally to micron-scale ordered ethanol aggregates. Fluorescence spectroscopy, two-dimensional correlation analysis and
nuclear magnetic resonance revealed the underlying non-
equilibrium molecular mechanism: a periodic perturbation of the water-dominated hydrogen-bond network initiates a ethanol-water coexistence intermediate, ultimately leading to the stable ordered assembly of an ethanol-rich phase. Our finding demonstrated that periodic physical perturbations capable drive spontaneous ordering across multiple length scales in a simple binary mixture, providing a kinetic perspective on the structural origin of solution non-ideality, and carry general implications for self-assembly strategies in soft matter.
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All authors Xinyue Jiang, Yating Shang, Jianhui Li, Zhaoyong Zou, Yanxia Zuo, Yuqun Xie
Materials Science
Local Structural Signatures of Shear Bands in Metallic Glasses via Electron Nanodiffraction
Huyen T. Pham, Daniel East, Chunguang Tang et al. (+4 more)
Structural changes in a glass due to deformation are subtle and difficult to quantify using conventional imaging and diffraction techniques. Additionally, transmission electron microscopy (TEM) sample preparation using energetic ions often causes structural modifications that are challenging to detect in disordered materials. By preparing inverted cross-sectional transmission electron microscopy lamellae of shear bands formed during bending, and employing cryogenic ion polishing to minimize preparation artefacts, we preserve the intrinsic atomic structure. Using sensitive, new parameters derived from electron nano-diffraction, we directly probe the local nano-scale structure in the plastic zone beneath surface shear steps in metallic glasses. Mapping of local centrosymmetry and strain reveals nanoscale, stripe-like regions oriented at 45 degree to the applied strain where strain has localized. These regions exhibit a high density of local atomic structures that have transformed to configurations with reduced centrosymmetry and increased magnitudes of shear and normal strain. Our results demonstrate that plastic deformation in metallic glasses arises from coordinated nanoscale structural transformations, providing direct experimental insight into a long-standing problem.
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All authors Huyen T. Pham, Daniel East, Chunguang Tang, Matteo Baggioli, Alessio Zaccone, Timothy C. Petersen, Amelia C. Y. Liu
Materials Science
Disentangling the contributions of individual cations to magnetic order in a spinel high entropy oxide
Mario Ulises González-Rivas, Chun-Fu Chang, Martin Bluschke et al. (+8 more)
High
entropy oxides (HEOs) can possess long-range ordered
magnetic states despite their extreme chemical disorder. Very little is known about how the different chemical constituents in HEOs contribute to the emergence of these
magnetic states. In this work, we leverage element-specific magnetometry attained via x-ray
magnetic circular dichroism (XMCD) to understand how
magnetic order is driven in two ferrimagnetic spinel-structured HEOs with compositions (Cr,Mn,Fe,Co,Ni)$_3$O$_4$ and (Cr,Mn,Fe,Co,Ni)$_{2.4}$Ga$_{0.6}$O$_4$. We find that while the
magnetic transition is simultaneous for all chemical species, the rate at which their
magnetic moments grow is strongly cation dependent. This behavior is explained by the varying $\textit{3d}$
crystal field level fillings of the
magnetic cations, which in turn determine their ability to participate in the different
magnetic exchange pathways available in the spinel structure. Dominant $A$-$B$ sublattice exchange enables some species to harden rapidly ($\textit{e.g.}$ tetrahedral Fe$^{3+}$ and octahedral Ni$^{2+}$) while others exhibit a sluggish transition due to frustration from competing interactions ($\textit{e.g.}$ octahedral Fe$^{3+}$ and Cr$^{3+}$). Non-
magnetic substitution suppresses these differences, introducing broken
magnetic linkages that relieve frustration. Tailoring the magnetism of HEO spinels therefore requires detailed knowledge of both their site selectivities and their exchange pathways.
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All authors Mario Ulises González-Rivas, Chun-Fu Chang, Martin Bluschke, Jessica Freese, Peter Bencok, Ronny Sutarto, Teak D. Boyko, Robert J. Green, George A. Sawatzky, Liu Hao Tjeng, Alannah M. Hallas