Strongly Correlated Electrons
NMR Determination of the Low-Field Magnetic Structure of the Cu-Based Mineral Rouaite Cu$_2$(OH)$_3$NO$_3$
Issei Niwata, R. Kumar, Aswathi Mannathanath Chakkingal et al. (+5 more)
Frustrated interactions in the Cu-based mineral rouaite with alternating
antiferromagnetic and
ferromagnetic spin chains, Cu$_2$(OH)$_3$NO$_3$, introduce non-trivial
magnetic ground states and exotic excitations arising from them. We investigated the
magnetic structure of Cu$_2$(OH)$_3$NO$_3$ by $^1$H- and $^2$H-NMR measurements on single
crystals. The internal fields in the ordered state were microscopically measured using the H
nuclear moments as a local probe. The directions of the ordered moments were determined by comparing the experimental results to model calculations. The obtained
magnetic structure suggests the importance of Dzyaloshinskii-Moriya interactions in stabilizing the low-field
magnetic structure. The present result advances the theoretical understanding of the low-field
magnetic states and will enable exploration of the exotic
magnetic states emerging in high
magnetic fields.
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All authors Issei Niwata, R. Kumar, Aswathi Mannathanath Chakkingal, Anton A. Kulbakov, Maxim Avdeev, Dmytro S. Inosov, Darren C. Peets, Yoshihiko Ihara
Strongly Correlated Electrons
Spin-liquid-like ground states in the double hydroxyperovskites CuSn(OD)6 and MnSn(OD)6 evidenced by {\mu}SR spectroscopy
Moumita Naskar, Anton A. Kulbakov, Kaushick K. Parui et al. (+9 more)
Double hydroxide perovskites with
magnetic transition-metal ions were recently identified as a unique class of materials that combine
magnetic frustration with correlated
proton disorder-a prerequisite for
quantum-disordered fluctuating
magnetic ground states resembling
spin liquids. Here we present the results of
muon spin relaxation ({\mu}SR) measurements carried out on fully deuterated samples of the double hydroxyperovskites CuSn(OH)6 (S = 1/2) and MnSn(OH)6 (S = 5/2) over the temperature range 0.053-50 K. The absence of any long-range
magnetic order is confirmed down to 0.053 K. We observe no oscillations of the
muon asymmetry down to the lowest temperature. The
muon relaxation rates show a continuous increase with decreasing temperature, indicating persistent
spin fluctuations in both compounds.
Spin correlations are consistent with homogeneous
spin dynamics. These observations reinforce the assertion that both compounds have a
quantum-dynamic
magnetic ground state that is consistent with a
spin-
liquid-like phase stabilized by
proton disorder.
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All authors Moumita Naskar, Anton A. Kulbakov, Kaushick K. Parui, Jonas A. Krieger, Thomas J. Hicken, Hubertus Luetkens, Ellen Häußler, Thomas Doert, Darren C. Peets, Hans-Henning Klauss, Dmytro S. Inosov, Rajib Sarkar
Superconductivity
4-Pixel NbN Hot-Electron Bolometer Integrated in a Si$_3$N$_4$ Planar Optical Waveguide with On-Chip Fiber-Alignment Trench
N.A. Vovk, G.A. Matveev, M.A. Mumlyakov et al. (+7 more)
In this work, we design and characterize a 4-pixel superconducting hot-electron bolometer (HEB) based on niobium nitride (NbN), integrated with individual planar silicon nitride (Si$_3$N$_4$) waveguides. The implemented architecture enables simultaneous detection of an optical signal in four independent channels. To efficiently couple optical radiation under cryogenic conditions, we employ an edge (end-fire) coupling approach using dedicated U-shaped grooves that provide accurate and stable positioning of an optical fiber with respect to the on-chip waveguide facet. The device responsivity is measured as a function of the HEB operating point. The measured voltage responsivity reaches $3800~\mathrm{V/W}$ at a modulation frequency of $3~\mathrm{GHz}$. We demonstrate detection of optically modulated signals in the gigahertz range. The developed fabrication route is promising for compact integrated receiver systems and low-noise cryogenic microwave transducers, including superconducting nanowire single-
photon detectors (SNSPDs).
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All authors N.A. Vovk, G.A. Matveev, M.A. Mumlyakov, M.V. Shibalov, I.A. Filippov, I.D. Burkov, S.D. Perov, N.V. Porohov, N.N. Osipov, M.A. Tarkhov
Superconductivity
Extremely weak electron-phonon coupling in Josephson junctions built on InAs on Insulator
Giorgio De Simoni, Sebastiano Battisti, Alessandro Paghi et al. (+2 more)
InAs-on-
Insulator (InAsOI) enables an effective superconducting proximity effect and extremely weak electron-
phonon (e-ph) coupling, allowing precise electronic-temperature control with minimal power. Using Josephson junction thermometry, we extract sub-Kelvin e-ph coupling parameters, confirming strong thermal decoupling and robust superconducting performance. The combination of weak e-ph interaction and full electrostatic tunability makes InAsOI a powerful platform for coherent caloritronics, ultrasensitive bolometry, single-
photon detection, and gate-controlled superconducting thermal
circuits.
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All authors Giorgio De Simoni, Sebastiano Battisti, Alessandro Paghi, Lucia Sorba, Francesco Giazotto
Mesoscale and Nanoscale Physics
Analogue black hole merger in a polariton condensate
D. D. Solnyshkov, V. Paquelier, C. Balmisse et al. (+1 more)
Analogue studies represent an important tool in modern Physics. In particular, analogue
gravity had a strong success in the recent years with the demonstrations of Hawking radiation and superradiance of analogue black holes in classical and
quantum fluids. So far, the metric of the analogue black holes was mostly fixed by the conditions of the experiment, preventing the simulation of any significant
evolution of their properties, such as the change of their mass, their spatial motion, gravitation attraction to other bodies, and, ultimately, black hole mergers. Polariton condensates represent a perfect setting for the analogue simulation of black hole
evolution and mergers because of the velocity-dependent losses creating a convergent flow associated with each
quantum vortex, which thus becomes an analogue black hole capable of spatial motion. We show that while two
vortices are unable to form a common horizon, four or more
vortices can exhibit a complete black hole merger, with the radius of the common horizon given by a simple geometrical law. We also discuss the difference between the horizon and the apparent horizon in these analogue black holes with quantized constituents.
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All authors D. D. Solnyshkov, V. Paquelier, C. Balmisse, G. Malpuech
Soft Condensed Matter
Influence of Bubble Lifetime on the Drying of Catalytically Active Sessile Droplets
Meneka Banik and Ranjini Bandyopadhyay
When colloidal droplets evaporate, suspended particles are redistributed by a competition between evaporation-driven capillary advection, interfacial Marangoni stresses and particle mobility, leading to diverse deposition patterns relevant to coating and self-assembly. While these mechanisms are well understood for passive suspensions, their interplay in chemically active colloidal systems remains less explored. Here, we investigate the drying dynamics of droplets containing catalytic polystyrene-platinum (PS-Pt) Janus particles in the presence of hydrogen peroxide (H2O2) fuel. H2O2 undergoes catalytic decomposition at the Pt hemisphere, resulting in the formation of oxygen (O2). By systematically varying H2O2 concentration, surface wettability and open versus confined drying conditions, we identify distinct transport regimes governed by the relative magnitudes of capillary flow and gas bubble-induced Marangoni convection. While time-resolved contact-angle measurements reveal substrate-dependent evaporation modes, an increase in catalytic activity promotes O2 bubble generation that locally reverses or disrupts outward particle transport. Closed drying conditions further modify evaporation rates and prolong bubble residence times, leading to transitions from peripheral accumulation to spatially uniform or centrally concentrated deposits. Bubble-induced Marangoni flow, controlled here by tuning substrate wettability and environmental conditions, therefore emerges as the dominant mechanism governing the evaporation dynamics and dried morphologies of catalytically active Janus particle droplets.
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Materials Science
Towards an understanding of magnesium in a biological environment: A density functional theory study
Miranda Naurin, Sally Aldhaim, Moltas Elliver et al. (+3 more)
Density functional theory is used to investigate the interactions between a layer of magnesium hydroxide, Mg(OH)2, the magnesium (Mg) surface Mg(0001), and the three amino acids glycine, proline and glutamine. The aim is to improve the understanding of Mg behavior in biologically relevant environments, such as the ones that biodegradable implants experience in the body. For a simple model of such conditions, adsorption of amino acids are studied. With the layer of Mg(OH)2 as a model of either slightly corroded Mg, or intentionally coated Mg, the interfacial interaction between a layer of Mg(OH)2 and Mg(0001) is first examined in the absence of the molecules. Then follows analyses that include amino acids on top of the Mg(OH)2 layer. We find that the Mg(OH)2/Mg(0001) interaction is weak and that the layer of Mg(OH)2 can readily slide across the Mg surface. The presence of amino acids is found to have a limited influence on the adsorption of Mg(OH)2 on Mg(0001), decreasing the binding by at most 3%, while more layers of Mg(OH)2 strengthen the Mg(OH)2/Mg(0001) binding by 13%. This is still less than the binding of Mg(OH)2 layers within its native bulk structure, and our findings indicate that only a small number of hydroxide layers are required before it is energetically more favorable for Mg(OH)2 to create bulk than to stay on Mg(0001) as single layers. This provides insight into early-stage surface processes relevant for magnesium-based implant materials.
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All authors Miranda Naurin, Sally Aldhaim, Moltas Elliver, Ludwig Hagby, J. Didrik Nilsson, Elsebeth Schröder
Statistical Mechanics
Magnetization plateaus, spin-canted orders and field-induced transitions in a spin-1/2 Heisenberg antiferromagnet on a distorted diamond-decorated honeycomb lattice
Katarina Karlova and Jozef Strecka
We investigate the
spin-1/2 Heisenberg antiferromagnet on a distorted diamond-decorated honeycomb
lattice in an external
magnetic field. By combining density-
matrix renormalization group, sign-problem-free
quantum Monte Carlo in a mixed dimer-monomer basis, exact diagonalization, and an effective
lattice-gas approach, we determine the ground-state phase diagram and analyze the finite-temperature magnetization process. The model hosts a rich variety of frustration-induced
quantum phases including a
quantum ferrimagnetic phase of Lieb-Mattis type, a
quantum ferromagnetic phase, a
spin-canted phase, a monomer-dimer phase, a dimer-tetramer
liquid, a dimer-tetramer solid, and two distinct one-dimensional-crossover phases of
ferromagnetic and ferrimagnetic character. Depending on the
lattice distortion, we identify robust magnetization plateaus at 0, 1/4, 1/2, and 3/4 of the saturation magnetization originating from competing local dimer and tetramer singlets. Finite-temperature QMC data reveal how thermal fluctuations progressively smear the plateau structure, while the effective
lattice-gas description reliably captures the corresponding low-temperature behavior.
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Materials Science
Time Resolved Study of Laser Induced Ultrafast Alloying Processes in Au/Pd Core Shell Nanorods
Abhisakh Sarma, Jayanath C. P. Koliyadu, Romain Letrun et al. (+16 more)
Femtosecond
laser-induced alloying presents a novel approach to modifying bimetallic systems. Visualizing ultrafast processes during
laser-induced alloying is essential to uncover fundamental mechanisms associated with phase transformations, which enables precise control over material composition and structure at the atomic level. In this study, we investigated the ultrafast dynamics of
laser-induced alloying of Au/Pd core-shell nanorods using a time-resolved X-ray diffraction technique at an X-ray free-electron
laser facility, capturing the structural
evolution from picoseconds to microsecond timescales. We found that a
laser fluence threshold of ~ 48 mJ/cm2 with 800 nm excitation is sufficient for melting and subsequent
alloy formation. Above this threshold, the formation of Au1.51Pd0.49 was observed, and we found that alloying is not a single-step phenomenon; instead, it is a dynamic process involving interdiffusion.
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All authors Abhisakh Sarma, Jayanath C. P. Koliyadu, Romain Letrun, Egor Sobolev, Trupthi Devaiah C, Agnieszka Wrona, Katerina Doerner, Diogo V. M. Melo, Marco Kloos, Huijong Han, Marcin Sikorski, Konstantin Kharitonov, Juncheng E, Joana Valerio, Pralay K. Santra, Erik M. J. Johansson, Richard Bean, Chan Kim, Tokushi Sato
Materials Science · Cross-listed from physics.chem-ph
Weiner's theory for exactly solvable Schrödinger equation with symmetric double well potential
A.E. Sitnitsky
The Weiner's theory (WT) is developed on the basis of the exactly solvable Schrödinger equation with trigonometric double-well potential (TDWP). The symmetric case of TDWP is considered. This modified version of WT (mWT) enables one to eliminate some severe approximations of the original Weiner's approach and to obtain more accurate results. An analytic formula is derived which provides the calculation of the
proton transfer rate with the help of elements implemented in {\sl {Mathematica}}. We exemplify the application of mWT by calculating the
proton transfer rate constant in the hydrogen bond of the
proton-bound ammonia dimer cation ${\rm{N_2H_7^{+}}}$ (${\rm{H_3N\cdot\cdot\cdot H^{+} \cdot\cdot\cdot NH_3}}$). The parameters of the model for this object are extracted from available literature data on IR spectroscopy and
quantum chemical calculations. The approach yields the transition from the Arrhenius-like exponential temperature dependence characteristic of thermal activation to that of
quantum tunneling. Besides it is well suited for describing the phenomenon of vibrationally enhanced tunnelling.
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Soft Condensed Matter
Ostwald's Rule of Stages in One-Dimension
Jiajun Chen, Ying Xia, Mingyi Zhang et al. (+2 more)
Ostwald's Rule of Stages, which is one of the most widely observed phenomena associated with crystallization of polymorphs, follows naturally from the thermodynamics of nucleation. However, most observations of its manifestations have been limited to three-dimensional
crystals and its validity in one-dimension, where no nucleation barrier exists, remains unclear. Here we investigate the two-dimensional assemblies and phase transformation mechanisms of a peptide that forms two distinct phases on graphite via one-dimensional nucleation using in situ atomic force microscopy. We find that the
evolution of phases illustrates Ostwald's Rule, but does so for purely kinetic reasons, and that the stable phase replaces the metastable via a dissolution-reprecipitation mechanism enabled by inherent fluctuations of the phase boundary. The findings provide general insights into the growth and transformation mechanisms of coexisting two-dimensional phases and thus delineate a strategy for capturing transient two-dimensional structures.
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All authors Jiajun Chen, Ying Xia, Mingyi Zhang, Yu Huang, James J. De Yoreo
Materials Science
Percolation-driven $\beta$ -relaxation enables resonant acceleration of crystallization in amorphous phase-change materials
Yu-Yao Liu, Liang Gao, Jun-Ying Jiang et al. (+9 more)
Amorphous phase-change materials enable fast and reversible switching in optical and electronic devices, yet crystallization kinetics are still controlled primarily through empirical thermal protocols. Here we identify a microscopic picture governing crystallization in the prototypical phase-change material Ge2Sb2Te5, in which crystallization pathways are organized by the percolation of mobile atomic networks associated with $\beta$-relaxation. We show that this percolation transition distinguishes the dominance of
diffusion-driven and diffusionless nucleation and growth during crystallization processes. We further demonstrate that frequency-selected ultrasonic excitation, applied in conjunction with heating, accelerates crystallization by enhancing percolation-mediated atomic dynamics. This acceleration is maximized near the $\beta$-relaxation frequency, consistent with resonant excitation of mobile atoms. Our results establish a direct link between glassy relaxation, atomic-scale percolation, and crystallization, and introduce a new route to modulating phase-change kinetics through targeted excitation of fundamental glassy dynamics.
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All authors Yu-Yao Liu, Liang Gao, Jun-Ying Jiang, Yiming Zhou, Jan Luebben, Di Zhao, Xiaoling Lu, Maximilian J. Müller, Ulrich Boettger, Jiang-Jing Wang, Hai-Bin Yu, Shuai Wei
Materials Science · Cross-listed from math.AP
Testing Hooke-like isotropic hyper-/hypo-elastic material models under finite simple shear deformations
Sergey N. Korobeynikov, Alexey Yu. Larichkin and Patrizio Neff
We test some Hooke-like isotropic hyper-/hypo-elastic material models under finite simple shear deformations (cf., Thiel et al. Int. J. Non-linear Mech. 112: 57–72, 2019) and show that (1) the components of the Cauchy stress tensor for any Cauchy/Green isotropic elastic material under left finite simple shear (LFSS) deformation are equal to the components of the rotated Cauchy stress tensor for the same material under right finite simple shear (RFSS) deformation; (2) for any Hill's linear isotropic hyperelastic material model based on a symmetrically physical (SP) strain measure, LFSS and RFSS deformations lead to Eulerian and Lagrangian pure shear stresses, respectively; (3) for any two-power Ogden's isotropic hyperelastic material model based on a SP strain function, LFSS and RFSS deformations lead to Eulerian and Lagrangian pure shear stresses, respectively; (4) for some Hooke-like isotropic hypoelastic materials with constitutive relations based on corotational stress rates under LFSS deformation, the behavior of the Cauchy stress tensor components as a function of the shear parameter is qualitatively similar to that for the same materials under simple shear deformation. In addition, we confirm the results of Lin (Lin R.C. ZAMP, 75: 191, 2024) showing that for some Hooke-like isotropic hypoelastic materials with constitutive relations based on corotational stress rates without initial stresses under RFSS deformation, the Cauchy stress tensor components coincide with those for the Hencky isotropic hyperelastic material.
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Materials Science · Cross-listed from physics.comp-ph
On the Intrinsic Link between Gradient Strengthening and Passivation Onset in Single Crystal Plasticity
Habib Pouriayevali
A finite-deformation framework for gradient
crystal plasticity is developed within a thermodynamically consistent setting grounded in Gurtin's power-conjugate formulation. The model introduces a flow rule that accounts explicitly for both energetic and dissipative microstress contributions. Numerical simulations are performed to investigate the response of single
crystals subjected to passivation-type boundary constraints. The results reveal that constitutive laws capable of reproducing size-dependent strengthening at the onset of plastic flow simultaneously generate a pronounced, nearly elastic-type response when passivation is imposed. These findings establish a fundamental connection between gradient-induced yield strengthening and boundary-driven elevation of the mechanical response, highlighting the essential influence of dissipative gradient effects.
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Mesoscale and Nanoscale Physics
Insulating Electronic States Near the Dirac Point Arising from Twisted Stacking and Curvature in 3D Nanoporous Graphene
Yoichi Tanabe, Hayato Sueyoshi, Samuel Jeong et al. (+3 more)
Twist-stacked
graphene with a twist angle $\theta$ of $\sim 5^\circ$–$30^\circ$ retains two-dimensional monolayer
graphene-like Dirac states near the Dirac point. In three-dimensional nanoporous
graphene (3D-NPG),
curvature inherently produces twist-stacking and topological defects required to form a porous network. When regions with $\theta \ge 5^\circ$ dominate, Dirac states in individual layers are expected to persist, allowing the Dirac-electron behavior to be tuned through coupling to the 3D curved geometry. However, predicted band gap formation or localized states have remained unobserved. Here we report that 3D-NPG maintains monolayer-like Dirac electronic states while simultaneously exhibiting insulating behavior near the Dirac point. Raman G-band softening confirms these monolayer-like states, and an Arrhenius-type temperature-resistance trend coexisting with weak localization near the Dirac point indicates partially insulating states induced by topological defects. These findings demonstrate that 3D-NPG hosts distinctive Dirac electronic states coupled to 3D
curvature, providing a platform for developing new functionalities in 3D
graphene-based electronics and energy devices.
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All authors Yoichi Tanabe, Hayato Sueyoshi, Samuel Jeong, Kojiro Imai, Shojiro Kimura, Yoshikazu Ito
Soft Condensed Matter · Cross-listed from math-ph
A Leibniz rule of distributional pairing and hyperforce sum rule
Takashi Maruyama, Tatsuki Seto, Viktor Zaverkin et al. (+1 more)
We reformulate and generalize the
equilibrium hyperforce sum rule, a generalization of the Bogoliubov-Born-Green-Kirkwood-Yvon (BBGKY) hierarchy, by employing the Schwartz space and its dual. We show that the hyperforce sum rule for the Euclidean space and the
equilibrium BBGKY hierarchy at arbitrary level are derived through the Leibniz rule of the derivative for the pairing of tempered distributions and Schwartz functions. We also apply the Leibniz rule to obtain the hyperforce sum rule for systems with periodic boundary conditions.
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All authors Takashi Maruyama, Tatsuki Seto, Viktor Zaverkin, Henrik Christiansen
Materials Science
Pressure-induced lattice instabilities and phonon softening in the orthorhombically distorted ferrimagnet Ni4Nb2O9
Rajesh Jana, Xinyu Wang, Takeshi Nakagawa et al. (+4 more)
The ambient- and high-pressure behavior of the ferrimagnet Ni4Nb2O9 (orthorhombically distorted honeycomb structure), is investigated using NMR, Raman spectroscopy, and synchrotron XRD. Ambient-pressure NMR measurements reveal, despite its orthorhombic
symmetry, the local environment of Ni4Nb2O9 closely resembles that of its trigonal analogue Mn4Nb2O9. In contrast, substantially different paramagnetic shifts observed in the two compounds reflect their distinct average
crystal symmetries, governing orbital overlap and
magnetic exchange pathways. Under external pressure, Ni4Nb2O9 exhibits pronounced sensitivity to
lattice distortions and
phonon instabilities. Three isostructural transitions are identified near 2, 6, and 10 GPa, manifested by mode splitting, frequency shifts, line broadenings, intensity anomalies, and slope changes in the
evolution of
lattice parameters. At higher pressure, around 13 GPa, signatures of an incipient long-range structural transition from orthorhombic Pbcn to monoclinic P2/c
symmetry emerge, signaling the onset of a
symmetry-lowering transformation. The anomalous softening of the 192 cm^-1 Raman mode, accompanied by multiple linewidth and spectral-weight anomalies, serve as a key fingerprint of these structural instabilities, linking local
symmetry breaking at low pressures to the long-range transition into the P2/c phase. Notably, pronounced linewidth anomalies, strongly anisotropic pressure coefficients, together with a marked enhancement of the intensity of the low-frequency branch over the 2-13 GPa range, point toward a pressure-induced regime influenced by coupled
spin, orbital, and
lattice degrees of freedom. The close correspondence of transition pressures in Ni4Nb2O9 and those reported for Mn4Nb2O9 highlights a common mechanism rooted in their similar local structural environments, as revealed by NMR.
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All authors Rajesh Jana, Xinyu Wang, Takeshi Nakagawa, Hirofumi Ishii, Alka Garg, Rekha Rao, Thomas Meier
Soft Condensed Matter
A hyperelastic theory for nonlinear hydrogel diffusiophoresis
Chinmay Katke and C. Nadir Kaplan
Hydrogel diffusiophoresis is the deformation of a hydrogel due to a solute gradient that leads to a gradient of pairwise interactions between the solute particles and the hydrogel
polymers to trigger osmotic flux. Unlike typical osmosis, it occurs without any interface selectivity of the gel to the solute and can overcome the diffusive swelling without any structural modifications to the gel. We have recently shown this effect for linear deformations of a chemically responsive polyacrylic acid (PAA) hydrogel that releases ions upon arrival of a stimulus (acid), thus internally generating the solute gradient required for diffusiophoresis [Phys. Rev. Lett. 132, 208201 (2024)]. Here we develop a nonlinear poroelastic theory for large diffusiophoretic gel strains in two models: Model I considers deformations of a generic gel when an external solute gradient is imposed and indicates that deformations can be stored while the stimulus gradient persists. Model II is concerned with the internal generation of the solute gradient within the gel, motivated by the coupled PAA gel, solute (copper), and stimulus (acid) system. In Model II, we investigate the nonlinear deformations for high stimulus concentrations or by changing the solute particle size to boost steric
polymer-solute interactions, as well as under a stimulus flow through the gel. Compared to the experimental strain rates in Katke [Phys. Rev. Lett. 132, 208201 (2024)], Model II demonstrates that varying the stimulus concentration can increase the strain rate up to four times, changing the solute particle size up to $\sim 25$ times, and imposed flow up to $\sim 40$ times. Our theory couples nonlinear poroelasticity,
polymer-solute interactions, and reaction-transport dynamics to predict large and fast diffusiophoretic gel deformations, which may find applications in hydrogel-based soft robotics and drug delivery.
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Mesoscale and Nanoscale Physics
Edge-controlled non-Hermitian skin effect in the modified Haldane model
Nobuhiro Ito and Shun Uchino
The hybrid skin-topological effect (HSTE) arises from the interplay between the non-Hermitian skin effect and topologically protected edge states. Here, we investigate the HSTE associated with antichiral edge states. As a minimal model, we study a modified Haldane nanoribbon in which gain and loss are applied exclusively at the zigzag edges. We show that in antichiral systems, the HSTE originates from the interplay between edge modes and counterpropagating bulk modes, a mechanism distinct from that in conventional
chiral systems. Remarkably, in sufficiently narrow ribbons, applying gain or loss to only one edge can induce a skin effect in states localized at the opposite edge. We refer to this phenomenon as a nonlocal antichiral skin effect. We further show that, in narrow systems, edge-localized dissipation can induce bulk skin modes when parity-time ($\mathcal{PT}$)
symmetry is broken, while the bulk non-Hermitian skin effect is forbidden in the $\mathcal{PT}$-symmetric regime. These results imply that edge-localized gain and loss can control both the emergence and the localization direction of the bulk skin modes. Our findings establish a
symmetry-based mechanism for controlling non-Hermitian skin effects via edge dissipation in antichiral systems.
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Disordered Systems and Neural Networks
Single impurity-induced localization transitions in electronic systems
Niaz Ali Khan, Munsif Jan, Muzamil Shah et al. (+3 more)
Anderson localization is a fundamental phenomenon in disordered
quantum systems, where transport is suppressed by wave interference from extensive randomness. Moving beyond traditional multi-
impurity scenarios, we investigate
impurity-induced localization phenomena in low-dimensional tight-binding systems by focusing on the properties of
impurity-generated bound states. By introducing a single on-site
impurity into an otherwise extended
lattice, we demonstrate that the
impurity can host a bound state whose spatial character undergoes a transition from extended to localized as the
impurity strength surpasses a critical value. This transition pertains solely to the
impurity state, while the bulk states of the host system remain extended. We characterize the localization behavior by analyzing two distinct spatial profiles of the bound states: one with symmetric decay and another with exponential decay from the
impurity site. Our results highlight how a local perturbation can induce nontrivial localization behavior at the level of individual eigenstates, without implying a global localization transition of the underlying electronic system.
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All authors Niaz Ali Khan, Munsif Jan, Muzamil Shah, Muhammad Sajid, Muhammad Mateen, Mushtaq Ali
Soft Condensed Matter
Curing-induced filler aggregation in epoxy-amine systems
Yujiro Furuta and Rei Kurita
Hypothesis: The macroscopic properties of
polymer composites are governed by the dispersion and aggregation states of filler particles within a crosslinking
matrix. Although curing transforms a
liquid precursor into a solid network, its influence on filler aggregation remains insufficiently understood. We hypothesize that curing induces effective attractive interactions between filler particles, leading to aggregation even in non-Brownian systems. Experiment: Fluorescent polystyrene beads were homogeneously dispersed in a bisphenol F epoxy resin. Curing was initiated by adding trimethylhexamethylenediamine, and the
evolution of the three-dimensional particle configurations was quantitatively examined using confocal
laser fluorescence microscopy before and after completion of curing. Findings: Aggregation was enhanced during curing despite the absence of conventional attractive forces. The aggregation increment cannot be described solely by filler volume fraction but is governed by the mean interparticle gap $H$. Data collapse onto a linear scaling with the reduced gap parameter, identifying a
geometric control parameter for curing-induced aggregation. This scaling demonstrates that curing dynamically generates an effective interaction whose spatial range scales with particle size, consistent with previously predicted
rigidity-percolation-induced attractions. These findings establish a
geometric criterion for predicting final dispersion states in curing
polymer composites.
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Materials Science · Cross-listed from physics.optics
Plasmonic- and Electronic-Enhancement-Free Coherent Raman Detection of Ångström-Scale Molecular Layers at Metal Interfaces
Toshiki Sugimoto, Tomoaki Ichii, Tsuneto Kanai et al. (+5 more)
Coherent Raman scattering provides highly sensitive vibrational analysis through nonlinear light-matter interactions. However, its application to metal interfaces has remained challenging because the intrinsically large non-resonant background (NRB) of metals overwhelms weak interfacial molecular vibrational signals, making direct Raman detection without plasmonic or electronic enhancement highly challenging. Here, we report a time-frequency hybrid coherent Raman spectroscopy approach that overcomes this limitation and enables sensitive detection of ångström-thick molecular systems even on atomically flat metal surfaces. Our method employs a time-frequency engineered detection scheme that combines femtosecond pump and Stokes pulses with a time-delayed, asymmetrically shaped picosecond probe pulse. By exploiting instantaneous temporal response of the metal NRB, this pulse configuration effectively filters out the dominant metal NRB in the time domain while retaining a controlled residual NRB that acts as an internal local oscillator, enabling strong interferometric amplification of weak interfacial vibrational signatures. This all-optical coherent enhancement strategy establishes a new route for direct, non-invasive Raman detection of interfacial molecular systems across a wide range of surfaces without requiring structure- and material-specific plasmonic and electronic enhancement mechanisms.
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All authors Toshiki Sugimoto, Tomoaki Ichii, Tsuneto Kanai, Ryu Yoshizawa, Shota Takahashi, Atsunori Sakurai, Keisuke Seto, Jin Chengxiang
Mesoscale and Nanoscale Physics
Valleytronics in 2D Materials Roadmap
Kyle L. Seyler, Giancarlo Soavi, Bent Weber et al. (+30 more)
Valleytronics exploits non-equivalent energy extrema in the electronic band structure of crystalline solids – the valley degree of freedom – to encode, manipulate, and read out information. The advent of 2D materials, first
graphene and then transition-metal dichalcogenides, made valley control practical through optical, electrical, and
magnetic routes. This foundation has enabled remarkable progress in recent years spanning established frontiers, such as valley
exciton physics and valley
Hall effects, as well as emerging directions including lightwave valleytronics, nanophotonic integration, flat-band valleytronics, and
spin-valley
qubits. In parallel, there are sustained efforts to scale up valleytronic materials and to predict new valleytronic platforms. This Roadmap brings together perspectives from leading experts to chart the key opportunities and challenges at the forefront of 2D material valleytronics. Each section captures a snapshot of progress in a key research area, identifies critical open challenges, and outlines pathways toward future valleytronics breakthroughs.
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All authors Kyle L. Seyler, Giancarlo Soavi, Bent Weber, Sunit Das, Amit Agarwal, Ioannis Paradisanos, Mikhail M. Glazov, Oleg Dogadov, Francesco Gucci, Giulio Cerullo, Stefano Dal Conte, Shubhadeep Biswas, Jan Wilhelm, Igor Žutić, Konstantin S. Denisov, Tong Zhou, Huiyuan Zheng, Wang Yao, Hongyi Yu, Ting Cao, Dacen Waters, Matthew Yankowitz, Guido Burkard, Artem Denisov, Thomas Ihn, Klaus Ensslin, Louis Gaudreau, Justin Boddison-Chouinard, Zlata Fedorova, Isabelle Staude, Kuan Eng Johnson Goh, Zhichao Zhou, Xiao Li
Materials Science
Designing a family of 2D kagome monolayer $B_{18}S_{8}$, $B_{18}S_{8}H_{2}$, $B_{18}S_{6}X_{2}$ (X=Cl,Br,I) with tunable Dirac cones and high Fermi velocity
Su-Yang Shen, En-Qi Bao, Xing-Yu Wang et al. (+2 more)
Two-dimensional (2D) kagome materials have become a hot research topic in the current scientific community due to their unique electronic structural properties, and the design of novel 2D kagome materials represents a significant exploration direction in this field. In this study, by employing the "1+3" design strategy, surface passivation and charge balance strategies, we successfully designed a novel family of 2D kagome material $B_{18}S_{8}$, $B_{18}S_{8}H_{2}$, $B_{18}S_{6}X_{2}$ (X=Cl,Br,I). Electronic structure analysis revealed that although $B_{18}S_{8}$ exhibits excellent kagome band characteristics, its Dirac cone is located approximately 1 eV above the
Fermi level, making it difficult to utilize. However, by surface hydrogen passivation, the Dirac cone can be effectively adjusted to the
Fermi level. Further research found that introducing halogen atoms to replace surface sulfur atoms can similarly adjust the position of the Dirac cone to the
Fermi level. The
Fermi velocities near the Dirac cone for these five materials reach as high as 2.69 to 3.07*$10^5$ m/s. Additionally,
spin-orbit coupling can open a bandgap of approximately 20 to 55 meV at the Dirac cone. Our research not only provides an outstanding example for the design of 2D boron-based kagome materials but also fully demonstrates the immense potential of such materials in the electronics field.
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All authors Su-Yang Shen, En-Qi Bao, Xing-Yu Wang, Jiafu Wang, Jun-Hui Yuan
Statistical Mechanics
Self-sustained Molecular Rectification without External Driving or Information
Jiantang Jiang
Rectifying thermal white noise into directed motion is generally believed to require the consumption of energy or information, as exemplified by Maxwell's demon-type feedback controllers. Here we demonstrate a molecular rectification mechanism that operates without any external energy or information flow. An ion-induced asymmetry between two
liquid-vapor interfaces creates unequal surface barriers, enabling the harvesting and redistribution of surface energy released during condensation. Molecular dynamics simulations show that this intrinsic kinetic asymmetry sustains a persistent net water flux. Our results suggest that asymmetric potential energy landscape alone can rectify thermal fluctuations, revising the conventional understanding of noise-driven transport.
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Materials Science
Probing Coordination Environments in Buried Oxides of Aluminum Josephson Junctions by Resonant X-ray Reflectivity
Paul Corbae, Alex Abelson, Shivani Srivastava et al. (+16 more)
Decoherence remains a critical obstacle to achieving high-fidelity, scalable superconducting
qubits, with the tunnel barrier of Josephson junctions a key source of loss. Here we apply resonant X-ray reflectivity to non-destructively probe the electronic structure of buried layers in Al/AlO$_x$/Al Josephson junctions. At the Al $K$-edge, energy-dependent modulations in the reflectivity maps enable Kramers-Kronig-constrained extraction of the layer-resolved atomic scattering factors. The analysis reveals that the barrier coordination evolves from more tetrahedral toward predominantly octahedral character with increasing oxidation pressure. At the interfaces, the lower metal-
oxide boundary is comparatively under-coordinated and disordered relative to the upper interface. Comparison with simulated X-ray absorption spectra identifies the dominant coordination motifs within the
oxide and its interfaces, providing depth-resolved structural insight that constrains microscopic models of two-level system formation. These results link growth conditions, local coordination environments, and junction electronic properties, demonstrating resonant X-ray reflectivity as a powerful tool for probing the microscopic materials properties of Josephson junctions and providing a materials-level framework for mitigating decoherence in superconducting
qubits.
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All authors Paul Corbae, Alex Abelson, Shivani Srivastava, Heemin Lee, Bevin Huang, Lyrik R-J Lee, Davis B. Rash, Cheng-Tai Kuo, Donghui Lu, Mihir Pendharkar, Loren D. Alegria, Tian T. Li, Keith G. Ray, Shannon P. Harvey, Apurva Mehta, David I. Schuster, Vincenzo Lordi, Paul B. Welander, Jun-Sik Lee
Mesoscale and Nanoscale Physics
Learning-Performance Evaluation of a Physical Reservoir Based on a Vortex Spin-Torque Oscillator with a Modified Free Layer
Kota Horizumi, Takahiro Chiba and Takashi Komine
In this study, we numerically evaluate the learning performance of a
vortex spin-torque oscillator (VSTO) with a modified free layer, called a modified VSTO (m-VSTO), in which an additional layer (AL) of smaller radius is stacked on the free layer, for physical reservoir computing. The
vortex-core dynamics are computed using the Thiele equation incorporating the potential deformation induced by the AL. We identify the edge of chaos from the maximal Lyapunov exponent and quantify the short-term
memory capacity (STMC) as well as the information processing capacity (IPC) in a time-multiplexed reservoir scheme. We find that the m-VSTO exhibits finite STMC and IPC in a low-current and low-field regime below the threshold current of the conventional VSTO, and can achieve up to approximately twice the IPC with about one quarter of the power consumption. The pulse-width dependence of the IPC can be further interpreted by combining an analytical estimate of the transient time with Lyapunov-exponent data. Longer pulse widths promote stronger recovery-induced contraction toward the groove-trapped orbit over a wide range of subthreshold currents. In contrast, this difference in contraction rate becomes less pronounced near the threshold current, where the transient time increases rapidly. Consequently, the IPC is enhanced in a stable regime with a negative Lyapunov exponent rather than exactly at the edge of chaos. These results suggest that engineering the potential landscape and pulse-width-dependent recovery dynamics enables low-power spintronic physical reservoirs.
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Materials Science · Cross-listed from physics.comp-ph
Update of PHYSBO: Improving Usability and Portability of Bayesian Optimization for Physics and Materials Research
Yuichi Motoyama, Kazuyoshi Yoshimi, Tatsumi Aoyama et al. (+3 more)
Bayesian optimization (BO) is widely used to accelerate physics and materials research, where objective function evaluations are computationally or experimentally expensive. While many BO frameworks focus on algorithmic efficiency, practical usability and portability are equally critical for sustained use in real research environments. PHYSBO is a
Bayesian optimization library designed to address these needs by enabling optimization over user-defined candidate pools and by supporting domain-specific problem settings. This paper presents the major updates introduced in PHYSBO versions 2 and 3, with a focus on improvements in usability, portability, and practical deployment rather than on new optimization
algorithms. In PHYSBO version 2, the software license was changed from GPL to MPL to improve compatibility with a wider range of research and software ecosystems. Building on this revision, PHYSBO version 3 introduces a set of implementation-oriented updates aimed at improving usability and portability, without modifying the core optimization
algorithms. These updates include improvements in computational performance and scalability, extended support for multi-objective optimization, the introduction of range-based policies for continuous-variable optimization, the removal of environment-dependent components such as tightly coupled Cython modules, and compatibility with NumPy 2. These improvements reduce the technical and organizational burden on users, enabling PHYSBO to be deployed across diverse computing environments and research workflows. By emphasizing portability and ease of integration while maintaining sufficient performance, PHYSBO version 3 is positioned as a sustainable research infrastructure for
Bayesian optimization in physics and materials science.
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All authors Yuichi Motoyama, Kazuyoshi Yoshimi, Tatsumi Aoyama, Kei Terayama, Koji Tsuda, Ryo Tamura