Mesoscale and Nanoscale Physics
Alejandro S. Gómez, Rafael A. Molina, Pablo Burset et al. (+1 more)
Achieving robust topological superconductivity with multiple Majorana channels is a key step for scalable topological
quantum computing. To this end, we investigate magnetically doped three-dimensional topological
insulator heterostructures proximitized by an s-wave
superconductor within a fully three-dimensional extended Bernevig-Hughes-Zhang framework that explicitly accounts for vertical confinement. We show that
magnetic exchange coupling, orbital mixing, and bulk band inversion cooperate to generate effective equal-
spin p-wave pairing channels supporting multiple chiral Majorana modes. The number of Majorana channels is determined by the confined modes in the vertical direction and the high-Chern-number phases of the normal state, which allows us to derive an analytical criterion for the emergence of the multiple-Majorana topological superconducting phases. The chiral Majorana modes remain robust against strong disorder and moderate
symmetry-breaking perturbations. We also demonstrate that a superconducting phase difference defining a vertical Josephson junction acts as a tunable parameter that controls the hybridization, minigap, and effective multiplicity of the low energy Majorana channels. Our results establish
magnetic three-dimensional topological-
insulator heterostructures as a promising platform for engineering multiple chiral Majorana modes.
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All authors Alejandro S. Gómez, Rafael A. Molina, Pablo Burset, Yuriko Baba
Mesoscale and Nanoscale Physics · Cross-listed from physics.optics
Exceptional Points in Photonics: From Non-Hermitian Physics to Applications
Fan Zhang, Nikolay Solodovchenko, Dmitrii N. Maksimov et al. (+5 more)
Open photonic systems provide a versatile platform for non-Hermitian physics, enabling control over complex spectra, transport, and light-matter interactions. Exceptional points (EPs), at which
eigenvalues and eigenvectors coalesce and the governing operator becomes defective, play a central role because they combine branch-point spectral
topology, nonanalytic perturbative response, and controllable eigenstate conversion. This Review provides a unified framework for EP photonics by systematically distinguishing exceptional degeneracies according to the underlying operator, spectral variable, boundary conditions, and experimentally accessible observables. We discuss
Hamiltonian EPs, absorbing EPs associated with scattering zeros, real-frequency scattering-
matrix and Jones-
matrix EPs, Bloch and Floquet EPs, and Liouvillian EPs in open
quantum systems. We review their spectral
topology, static and dynamical encircling, higher-order exceptional structures, and coexistence with bound states in the continuum, together with applications in sensing, lasing, coherent absorption, directional scattering, polarization and wavefront control, nonlinear optics, optical storage, nonreciprocal photonics, and
quantum photonics. We also critically assess the current limitations, practical challenges, and future perspectives of EP-based photonic technologies, with particular
attention to robustness, noise, scalability, and experimentally measurable performance.
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All authors Fan Zhang, Nikolay Solodovchenko, Dmitrii N. Maksimov, Xuchen Wang, Mingzhao Song, Filippo Capolino, C. T. Chan, Andrey Bogdanov
Mesoscale and Nanoscale Physics
Interferometry reveals spin-singlet fractional quantum Hall edges in graphene
R. Ayache, K. Kim, M. Kuiri et al. (+7 more)
The edge modes of
spin-singlet fractional
quantum Hall (FQH) phases are manifestations of multicomponent topological order and SU(2)
spin symmetry. An archetype is the
spin-unpolarized state at $\nu$=2/3, whose edge is expected to host spatially coexisting yet counter-propagating charge and neutral
spin modes. Despite efforts, its edge properties, including
spin coherence and
spin-charge separation, have remained elusive owing to the difficulty of resolving
spins in FQH edge transport. Here, we develop a
spin-sensitive probe of
graphene FQH edges by using a p-n junction to interface a target FQH state with a probe integer
quantum Hall (QH) state of opposite polarity. An Aharonov-Bohm (AB) interferometer forms along the interface, when the target and probe edge channels carry the same
spin. We identify the
spin-unpolarized and polarized edges of the $\nu$=2/3 states at lower and higher
magnetic fields, respectively, through
spin-dependent interference. A novel multiparticle AB interference between two electrons of opposite
spin emerges from
spin-charge separation and recombination on the unpolarized edge, featuring a
spin swap. Our results establish edge transport as a probe of
spin-singlet topological orders, with implications for parafermion platforms in
graphene-
superconductor hybrids.
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All authors R. Ayache, K. Kim, M. Kuiri, Q. Benichou, H. Chakraborti, L. Pugliese, K. Watanabe, T. Taniguchi, H.-S. Sim, P. Roulleau
Materials Science
Geometry-Controlled Magnetic and Electronic Landscapes in Anisotropic van der Waals Materials
Maciej Śmiertka, Ewelina Cybula, Oliwia Janikowska et al. (+10 more)
Electronic structure in van der Waals materials is commonly engineered through composition, strain, electrostatic gating and
heterostructure assembly. Here we introduce geometronics, a concept in which substrate geometry locally reorients an anisotropic
crystal, transforming homogeneous external perturbation into programmable
magnetic and electronic landscapes. We demonstrate this concept using a bilayer of the antiferromagnetic
semiconductor CrSBr transferred onto an inverted pyramidal nanoindentation, where the local
crystal orientation with respect to the external
magnetic field drives the coexistence of antiferromagnetic and ferromagnetic phases within a single continuous
crystal. The resulting
magnetic landscape creates a switchable excitonic potential well of up to 10–12 meV, directly visualised by spatially resolved spectroscopy. More generally, geometronics provides a universal route for deterministically programmed electronic and
magnetic landscapes without modifying the material itself. It therefore establishes substrate topography as a new design principle that exploits the intrinsic anisotropy of layered van der Waals materials.
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All authors Maciej Śmiertka, Ewelina Cybula, Oliwia Janikowska, Bartosz Hołyński, Gayatri, Grzegorz Krasucki, Mariusz Hasiak, Kseniia Mosina, Zdenek Sofer, Adam Babiński, Maciej R Molas, Paulina Plochocka, Michał Baranowski
Superconductivity
Thermodynamics of $T_{\rm c}$ suppression in far-overdoped Tl$_2$Ba$_2$CuO$_6$
Ayanesh Maiti, David M. Broun, Seunghyun Khim et al. (+7 more)
The physical origin of the suppression of superconductivity with hole doping in overdoped cuprates remains unclear. We measure the electronic specific heat of microgram-scale Tl$_2$Ba$_2$CuO$_6$
crystals and find sharp superconducting anomalies persisting far into the overdoped regime. A weak-coupling BCS-like framework incorporating the known Fermi surface and cation disorder quantitatively reproduces the observed anomalies for $T_{\rm c}=14$-$25$ K and their weak doping dependence. The results show $T_{\rm c}(p)$ to be driven predominantly by a smoothly decreasing pairing strength.
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All authors Ayanesh Maiti, David M. Broun, Seunghyun Khim, Michal Moravec, Antony Carrington, Carsten Putzke, Vivek Mishra, Peter Hirschfeld, Andrew P. Mackenzie, Andreas W. Rost
Materials Science
Autonomous discovery of new structure-plausibility laws for explainable and rapid crystal diagnosis and screening
Zhilong Song and Lixue Cheng
Crystal generators and tool-using
agents propose structures faster than density functional theory (DFT) energy and
phonon calculations or experiments can assess them. Deciding which candidates merit expensive assessment is therefore the bottleneck, yet most screens test little beyond atomic overlap and give no chemical reason for failure. Here, our
agents generate, test and actively refute two million candidate laws, leaving eight Plausibility Rules for Inorganic Structures (PRIS). These laws encode five mechanisms: short-range repulsion, ionic contact and packing, electrostatic balance, bond-valence conservation and crystallographic site complexity. Experimental structures satisfy our law sets at 82–99%, but satisfy Pauling's rules 2–5 together at only 6.5%. The strictest set detects 87.9% of damaged
crystal structures, whereas distance cutoffs detect only 1.6–3.2%. PRIS plausibility is linearly correlated with synthesizability, so the PRIS-derived synthesis score (PSS) explainably screens 83.7% of hard-to-synthesize structures while retaining 80.7% of experimental structures. In a property-conditioned inverse-design run, PRIS and PSS can reduce the DFT validation queue by up to 67.3% and keep 99.2% of the candidates whose DFT-validated bulk moduli reach the design target. Beyond screening, PRIS explains why GNoME remains enriched in rare low-
symmetry structures and reveals how wrong-element assignments in falsified
crystal reports hide behind plausible coordinates. PRIS moves screening from a pass-or-fail verdict to a chemical reason for failure, showing that autonomous
agents can discover, by active refutation, physicochemical laws that guide calculations and experiments.
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Statistical Mechanics
Dynamical phase transitions for single particles in the semiclassical and weak noise limits
Norayr Asriyan, Jan Meibohm, Vasco Cavina et al. (+1 more)
We present a unifying description of dynamical phase transitions in the
unitary evolution of an isolated
quantum particle and the dissipative relaxation of a classical Brownian particle, based on a dynamical generat- ing function. In the semiclassical and weak-noise limits, Fisher zeros of this function condense in the complex- time plane and reach the corresponding physical axes, producing dynamical phase transitions through a competition between return trajectories. This establishes a direct connection between
quantum and classical (finite-time) dynamical phase transitions, where the semiclassical limit plays the role of the thermodynamic limit. In particular, the established link naturally provides a classical version of the Loschmidt amplitude and shows how dynamical
quantum phase transitions, typically associated with isolated many-body systems, can arise in a single-particle
quantum system. The dynamical phases are distinguished by a unifying, trajectory- based order parameter, realized as a classical correlation function and a sequential
quantum weak value.
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All authors Norayr Asriyan, Jan Meibohm, Vasco Cavina, Massimiliano Esposito
Mesoscale and Nanoscale Physics
Layer-selective and magnetic-field-enhanced transport of topological kink states in rhombohedral multilayer graphene
Chengyu Shen and Zhe Hou
Topological valley kink states (VKSs), which are
quantum valley Hall states emerging at the interfaces between adjacent domains with opposite valley Chern numbers, have attracted considerable interest in
graphene-based systems. In this work, we investigate the
quantum transport of VKSs in ABC-stacked rhombohedral multilayer
graphene in the presence of Anderson disorder and a perpendicular
magnetic field. Two prominent transport characteristics are revealed. First, in the absence of a
magnetic field, the kink states exhibit strong layer polarization, with their wave functions predominantly localized and equally distributed on the outermost top and bottom layers. As a result, their transport properties are highly sensitive to the layer-selective disorder distribution. Second, under a perpendicular
magnetic field, the layer-symmetric spatial distribution of VKSs is broken, leading to a significant reduction in the wave-function overlap between counter-propagating VKSs from opposite valleys. Consequently, intervalley scattering is suppressed, and the transmission of VKSs through disordered regions is substantially enhanced. Our results provide new insights into multichannel topological valley transport in rhombohedral multilayer
graphene and demonstrates disorder-engineering and
magnetic fields as effective approaches for manipulating the propagation of VKSs.
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Soft Condensed Matter · Cross-listed from nlin.PS
Chemotaxis-induced linear instabilities and pattern formation in a reaction-diffusion model
Mintu Karmakar and Abhik Basu
We study linear instabilities and pattern formation in a spatially extended Selkov model for glycolysis with
diffusion and chemotactic interactions between two species. Linear stability analysis reveals two distinct bifurcations: a zero-wavevector, finite-frequency Hopf bifurcation leading to spatially homogeneous oscillations, and a finite-wavevector Turing instability with a saddle-node bifurcation leading to stationary inhomogeneous patterns. The selected wavevector, $k_c$, depends sensitively on the nature and strength of chemotaxis and varies nonmonotonically with the chemotaxis parameters, allowing re-entrant transitions between homogeneous and patterned states. For sufficiently strong chemotaxis, when the two species mutually attract or mutually repel each other, an unusual instability emerges in which the preferred wavevector diverges as a finite threshold in chemotactic strength is approached. We complement the linear analysis with extensive direct numerical simulations (DNS) of the nonlinear partial differential equations in two dimensions. The DNS confirm the predicted instabilities and their nonmonotonic and re-entrant character, and also reveal spatially uniform oscillatory states for suitable parameters. The stationary patterns include spots and, unexpectedly, stable stripes. We further uncover transitions between spot and stripe morphologies controlled by chemotactic strength and diffusivity ratios. The stability of the striped states is consistent with linear amplitude equations, whereas the spot-stripe transition is attributed to nonlinear effects beyond linear stability. Our results demonstrate that chemotaxis can act as a nonmonotonic control parameter for instability selection, wavelength selection, re-entrant pattern formation, and nonlinear pattern morphology in reaction-
diffusion systems.
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Mesoscale and Nanoscale Physics
Probing Nonlinear Interactions of Dipolar Interlayer Excitons in MoSe$_2$/WSe$_2$ Heterobilayers
Sai Shradha, Luc F. Oswald, Md Tarik Hossain et al. (+10 more)
Interlayer
excitons in transition-metal dichalcogenide heterobilayers possess intrinsic out-of-plane dipole moments, providing a platform for investigating
exciton-
exciton interactions at high densities. Here, we use excitation-energy-dependent photoluminescence excitation (PLE) spectroscopy to probe the nonlinear response of dipolar interlayer
excitons in chemical vapor deposition-grown MoSe$_2$/WSe$_2$ heterobilayers. By tuning the excitation energy across intralayer
exciton resonances at fixed excitation power, we selectively vary the population injected into the interlayer
exciton states. Resonant excitation drives the system into a nonlinear regime, leading to saturation of the interlayer
exciton photoluminescence and an apparent broadening of the intralayer $1s$ resonances in the PLE spectra. At the same time, the interlayer
exciton emission exhibits a pronounced blueshift, reaching approximately 2.5 meV at 4 K and 1 meV at 75 K. The blueshift increases systematically with the interlayer
exciton population and is consistent with a net repulsive
exciton-
exciton interaction, with contributions from dipole-dipole repulsion in the density regime investigated. Our results establish PLE as a sensitive approach for accessing the nonlinear, high-density regime of interlayer
excitons and probing their interactions in van der Waals
heterostructures.
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All authors Sai Shradha, Luc F. Oswald, Md Tarik Hossain, Lukas Krelle, Nicole Engel, Axel Printschler, Julian Führer, Honey Jayeshkumar Shah, Daria I. Markina, Kenji Watanabe, Takashi Taniguchi, Andrey Turchanin, Bernhard Urbaszek
Quantum Gases
Quantum antidipolar systems in two-dimensional geometries
Juan Sánchez-Baena and Jordi Boronat
Particles with
magnetic moment can be polarized, and rapidly rotated, employing a
magnetic field such that the dipolar interaction among them changes sign, becoming antidipolar and thus isotropically attractive in a plane. Polar molecules can also be manipulated using microwave dressing fields to invert the sign of the dipole-dipole interaction. In this work, we study a two-dimensional system of antidipolar particles by calculating its equation of state and structural properties. The system behaves as a
liquid even for scattering lengths significantly greater than the dipolar length. For large enough densities, the system transitions to a solid with one particle per
lattice site via a first-order phase transition at a significantly smaller density than its dipolar counterpart. Moreover, motivated by the recent realization of a strongly axially trapped, bilayer geometry [Science 384, 546-551 (2024)], we study the properties of the bilayer
liquid phase as the inter-layer distance is tuned, and provide the range of parameters where one layer can influence the properties of the other.
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Statistical Mechanics
Re-entrance or monotonic: How chemotaxis controls pattern formation
Mintu Karmakar and Abhik Basu
We investigate pattern formation in generic two-species reaction-
diffusion systems with mutual chemotaxis. We show that tuning the chemotaxis strength can give rise to striking nonmonotonic variation of patterns, opening the possibility of re-entrant transitions between patterned and spatially uniform steady states. In certain regimes, chemotaxis also induces additional heretofore unexplored instabilities. Furthermore, varying the strength of chemotaxis can drive morphological transitions between spot and stripe patterns.
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Mesoscale and Nanoscale Physics · Cross-listed from physics.ins-det
Helium-Gas-Cooled Cryogenic Current Comparator Integrated with a Quantum Resistance Standard
Yuma Okazaki, Takehiko Oe and Nobu-Hisa Kaneko
We report a cryogen-free cryogenic current comparator (CCC) system for precision resistance measurements. A helium-gas chamber was developed and installed on the 4 K stage of a cryogen-free dilution refrigerator equipped with a pulse-tube cryocooler. The CCC probe was housed in this chamber and was cooled through helium gas serving as a heat exchange medium. The metrological performance of this helium-gas-cooled CCC was evaluated through precision resistance-ratio measurements and found to be comparable to that obtained under
liquid-helium cooling. A
quantum Hall resistance (QHR) device was also integrated into the same refrigerator, enabling QHR/100~$\Omega$ resistance-ratio measurements. The type-A uncertainty reached the 1~n$\Omega$/$\Omega$ level within an averaging time of 100~s, and the resulting resistance-ratio measurements agreed well with conventional
liquid-helium-based measurements at the level of a few n$\Omega$/$\Omega$. The system provides this level of measurement performance while consuming less than 1~L of helium gas per thermal cycle.
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Mesoscale and Nanoscale Physics
Interfacial orbital torques excite nanoscale terahertz magnons
Harshita Devda, Peter M. Oppeneer and Ulrich Nowak
Exchange-dominated
magnons in nanometer-thick ferromagnets extend to the terahertz regime through thickness quantization of perpendicular standing
spin-wave (PSSW) modes. While interfacial
spin-orbit torques (SOTs) have been shown to enable the excitation of such modes, the microscopic origin of the interfacial driving torque remains unclear. In particular, the coexistence of
spin and orbital currents complicates the understanding. Here, we develop and use an atomistic framework that explicitly resolves interfacial
symmetries and separates
spin and orbital torque contributions. Exploiting a trilayer geometry for a thin ferromagnet sandwiched between non-
magnetic layers, where the
symmetry-controlled polarity of the interfacial torque produces mode-selective
magnon excitation as observed in the recent experiment of Salikhov et al. Nature Phys. 19, 529 (2023), we disentangle the different interfacial torque contributions. By decomposing the torque into magnetization-even (field-like) and magnetization-odd components, we identify the field-like torque as the dominant contribution responsible for the excitation. Crucially, isolating orbital and
spin contributions reveals that the interfacial orbital torque provides the primary channel for the efficient excitation of exchange-dominated THz
magnons in thin ferromagnets. Our results establish a microscopic basis for
symmetry-engineered control of confined terahertz
spin dynamics in
magnetic multilayers.
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Materials Science
Pressure-regulated mechanochemistry at lithium metal-sulfide electrolyte interfaces
Kunik Jang, Jaehwan Choi, Jang Wook Choi et al. (+1 more)
Stack pressure is commonly treated as a means of maintaining physical contact in all-solid-state lithium-metal batteries, but it can also alter the chemistry of reactive solid-solid interfaces. Here, using pressure-aware, charge-resolved machine-learning molecular dynamics validated against DFT, we determine how pressure magnitude and loading geometry regulate interphase formation at Li||Li6PS5Cl interfaces. The response is nonmonotonic: compression at 1 kbar accelerates PS4 decomposition and Li2S-like ordering, whereas 10-100 kbar compression restricts structural rearrangement and long-range crystallization. Charge-resolved dynamics further identify sulfur-centered, lithium-rich early-interphase environments associated with subsequent Li2S-like ordering. Uniaxial loading accelerates interfacial reaction relative to isostatic loading at the same nominal pressure. Pressure also changes void closure and dead-lithium spreading in a defect-location-dependent manner. These results establish applied pressure as a mechanochemical process variable coupling interphase chemistry, ion transport and defect
evolution, providing a mechanistic framework for interpreting pressure effects in sulfide solid-state batteries.
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All authors Kunik Jang, Jaehwan Choi, Jang Wook Choi, Yousung Jung
Materials Science
Trap Dynamics and Conductivity Changes in AlGaN/GaN Heterostructures Under Ultrasonic Loading
Vladyslav Kaliuzhnyi, Mykola Tymochko, Oleksandr Gudymenko et al. (+2 more)
AlGaN/GaN
heterostructures are critical for high-power electronic devices but suffer from electron trapping at defects, limiting reliability. We investigate how ultrasonic vibrations affect electron transport in MOCVD-grown AlGaN/GaN
heterostructures by combining temperature-dependent Hall effect and high-resolution X-ray diffraction measurements. Here we demonstrate that ultrasonic loading induces persistent acoustoconductivity and
lattice parameter changes, attributed to acoustically driven rearrangement of metastable DX centers. This leads to increased carrier concentration and decreased mobility, reflecting defect state modulation by acoustic strain. These findings provide new insights into trap dynamics under dynamic deformation and suggest ultrasonic treatment as a potential approach to mitigate trapping effects, thereby enhancing the performance and reliability of GaN-based devices.
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All authors Vladyslav Kaliuzhnyi, Mykola Tymochko, Oleksandr Gudymenko, Oleg Olikh, Alexander Belyaev
Statistical Mechanics
Statistical Language Competition Model with Dynamic Edge Weighting on a Random Network
Somyaranjan Chakra, Mohit Anand Madhesia and Shradha Mishra
This paper presents a computational study of
language competition dynamics on Erdős–Rényi random networks, extending the foundational Abrams–Strogatz model through two novel contributions: (i) a dynamic edge-weighting mechanism that reinforces social ties between co-minority speakers by an additive increment $\Delta$, and (ii) a probabilistic
agent-based framework governing
language switching via a weighted majority rule. Phase boundaries separating the dominance and coexistence regimes are identified across a two-dimensional parameter space $(p, \Delta)$, where $p$ denotes the network connectivity probability. We further characterise anomalous persistence zones within predicted dominance regions, attributing them to the formation of isolated minority speaker clusters. Scaling study across network sizes $N \in \{50, 100, 250, 500, 1000\}$ reveal that average cluster size decreases with $N$ and that phase boundaries diffuse with increasing
stochastic noise. Finally, we discuss extensions to a tripartite bilingual model and heterogeneous prestige/
volatility to more faithfully capture real sociolinguistic contact scenarios.
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Materials Science
Text-guided flow matching enables sample-efficient crystal structure generation
Wentao Li
Crystal generators can now propose periodic structures, but their control interfaces remain poorly matched to the mixed descriptors used in materials design. Text provides a compact way to combine composition,
symmetry, prototype and property cues, yet it has not been clear whether such information can steer flow-based
crystal generation. Here we introduce TFMat, a text-conditioned flow-matching framework that uses structured materials
language as a semantic prior for a CrystalFlow generator. Across Perov-5, Carbon-24 and MP-20
crystal structure prediction
benchmarks, TFMat improves one-candidate match rates over CrystalFlow and reaches a 92.04% MP-20 match rate with 20 candidates; in de novo generation, it improves element-count and density distribution
alignment while retaining coarse property consistency in composition-selected outputs. These results position structured text as an inspectable control layer for translating human-readable materials intent into candidate
crystals for downstream simulation and validation.
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Materials Science
Exchange striction determines how fast antiferromagnetic insulators demagnetize
Aleksandr Buzdakov, Ravi Kaushik, Nikolai Khokhlov et al. (+2 more)
Antiferromagnets combine terahertz
spin dynamics with insensitivity to stray fields, and how quickly their order can be manipulated sets the speed limit on device operation. Femtosecond optical pulses demagnetize antiferromagnetic
insulators on timescales that span picoseconds to nanoseconds across compounds, and no material parameter is known that accounts for the spread or predicts where a new compound will fall. In a compensated antiferromagnet, no angular momentum needs to leave the
spin system, so the rate is set by energy flow from the
lattice into the
spins. Time-resolved second-harmonic generation experiments show that Cr2O3 demagnetizes within 2 ps once the
lattice is driven above the Neel temperature, two orders of magnitude faster than the structurally similar FeBO3. First-principles calculations trace the disparity to exchange striction: short Cr-Cr contacts make the exchange coupling tenfold more sensitive to atomic displacements and widen the phase space for
phonon decay into
magnon pairs.
Spin-
lattice simulations with ab initio parameters reproduce the order of magnitude of the measured ratio. The derivative of the exchange coupling with respect to the ionic displacement thus emerges as a computable parameter that predicts how fast an insulating antiferromagnet can be demagnetized. The results advance our understanding of ultrafast control in insulating antiferromagnets, and suggest a practical pathway to screen candidate materials for thermally assisted antiferromagnetic
memory before synthesis.
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All authors Aleksandr Buzdakov, Ravi Kaushik, Nikolai Khokhlov, Sergey Artyukhin, Alexey Kimel
Materials Science
First-Principles Electronic Structure Calculation of Crystals in Laboratory Magnetic Fields
Sichao Wang, Chengye Lü, Xingao Gong et al. (+2 more)
External
magnetic fields can qualitatively reshape the electronic structure of
crystals, underpinning
quantum Hall physics, Landau-level spectra and field-induced topological phases. Their first-principles treatment at laboratory-scale fields is, however, hindered by
magnetic-flux quantization, which requires
magnetic unit
cells with areas inversely proportional to the applied field. Such
cells contain a large number of chemical unit
cells, rendering real-space and plane-wave calculations prohibitively expensive. Here we, for the first time, construct a
magnetic Bloch basis built from linear combinations of gauge-including Gaussian-type atomic orbitals, which incorporate the
magnetic-field phase factors required by
magnetic translation
symmetry. The framework requires far fewer basis functions than real-space or plane-wave representations of the same
magnetic supercell and retains the sparsity of an atom-centred basis, together substantially reducing computational cost. We validate the framework by reproducing Landau-level spectrum of
graphene from first principles. This approach provides a practical route to simulations of crystalline materials under experimentally accessible
magnetic fields.
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All authors Sichao Wang, Chengye Lü, Xingao Gong, Yingwei Chen, Hongjun Xiang
Soft Condensed Matter
Mass-conserving growth percolation in polymer gelation
Ameya Rege and Lorenz Ratke
Polymer gelation involves the emergence of a system-spanning network from growing
polymer-rich domains, yet conventional percolation models typically prescribe particle size independently of material consumption. We formulate gelation as a locally mass-conserving growth-percolation process in which Voronoi capture zones define finite material reservoirs for individual
nuclei. Local depletion determines the evolving supersaturation and limiting particle size, while particle contacts generate a dynamic network whose first spanning cluster defines the gel point. Three mechanisms, namely, interface-,
diffusion-, and
polymer-blob-controlled growth produce distinct gelation kinetics while sharing the same accessible final state. Spatial fluctuations in nucleation further generate a distribution of gelation times. The framework separates gelation from saturation and naturally captures post-gel aging as continued growth and topological maturation.
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Mesoscale and Nanoscale Physics · Cross-listed from quant-ph
Tangent fermions can restore vacuum stability of discrete-time Dirac models
C.W.J. Beenakker
The Dirac
quantum walk (a 1+1 dimensional space-time discretization of the Dirac equation) has a $2\mu$ mass gap both at the center and at the corner of the quasi-energy-momentum Brillouin zone. Gupta and Short recently noted [
Quantum 9, 1845 (2025)] that the Dirac
vacuum can create a particle-hole pair at the zone corner with the release of an energy $2\mu$ to the environment. They removed this
vacuum instability at the expense of
fermion doubling, the appearance of a second low-energy Dirac cone. Here we show that an alternative discretization scheme, with a tangent rather than a sine dispersion relation, offers stability while retaining a single Dirac cone. The key step is the Cayley transformation from the unit circle of Floquet
eigenvalues $e^{-i\varepsilon}$ to the real line of unbounded energies $E=2\tan(\varepsilon/2)$. We compute the Schwinger effect (particle-hole pair creation in a uniform electric field) for tangent
fermions and show that the pair-production rate agrees with the continuum result for a single Dirac cone. The zone corner is exactly decoupled if the scalar potential is coupled through the Hermitian generator of the
quantum map. If it is coupled as a split operator, in order to preserve exact gauge invariance on the
lattice, the corner does contribute - with a weight that vanishes quadratically with the
lattice constants, in contrast to the Dirac
quantum walk where the zone-corner instability survives the continuum limit.
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Materials Science
Numerical study of the grain-growth-induced non-parabolic kinetics of a solid-state reaction
Ya. A. Nikiforov, S. A. Chizhik and N. I. Baklanova
Non-parabolic growth of reaction layers is frequently observed in solid-state
diffusion couples, but the relationship between microstructural
evolution and the resulting kinetics remains incompletely understood. This effect is commonly attributed to grain growth, which can progressively reduce the contribution of fast grain-boundary
diffusion, causing the effective diffusivity of a polycrystalline product layer to evolve during reaction. This work develops a moving-boundary
diffusion model to describe product-layer growth while accounting for the local grain-growth history of the continuously formed product, as well as both bulk and grain-boundary
diffusion. Numerical simulations show that the reaction can pass through three distinct kinetic regimes: an initial approximately parabolic regime dominated by grain-boundary
diffusion, a transient sub-parabolic regime associated with strong spatial variation of the effective diffusivity, and a subsequent approximately parabolic regime dominated by bulk
diffusion. The magnitude and duration of the sub-parabolic regime depend on the relative grain-boundary and bulk diffusivities and on the kinetics of grain growth. The instantaneous growth exponent therefore evolves continuously and does not represent a unique kinetic constant. Nevertheless, fitting simulated layer-thickness data over finite experimental time intervals produces well-defined apparent exponents, demonstrating how a transient process can appear to obey a single power law.
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Quantum Gases · Cross-listed from physics.optics
Topological charge switching in trapped polariton condensates
Jaewon Kim, Hyun Gyu Song, Daegwang Choi et al. (+1 more)
Topological charges in photonic systems provide a robust degree of freedom with direct applications in optical information processing. Bound states in the continuum (BICs) in photonic
crystal slabs inherently carry such quantized topological charges, yet they are topologically protected, making active reconfiguration fundamentally challenging. Here, we demonstrate topological charge switching in trapped BIC polariton condensates in a photonic
crystal, where spatial modulation of the photonic
crystals supports multiple confined states, each carrying a distinct charge. Trapped condensates within the Dirac bandgap are expelled into the leaky band via polariton blueshift, enabling single-mode selection by solely tuning the excitation power. This work offers a platform for optically controlling topological charges by harnessing polariton nonlinearity.
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All authors Jaewon Kim, Hyun Gyu Song, Daegwang Choi, Yong-Hoon Cho
Statistical Mechanics · Cross-listed from quant-ph
Information geometry of non-equilibrium quantum states: Mixed metric structures on an extended information manifold
Kouji Kashiwa and Hidefumi Matsuda
We discuss an information-
geometric framework for characterizing
quantum states in non-
equilibrium dynamics. Using the transverse-field Ising chain model as a laboratory, we investigate the
quantum Fisher information metric with particular emphasis on the mixed metric component $g_{ht}$ and related
geometric observables, where $h$ is a controllable post-quench
Hamiltonian parameter and $t$ is real time. The framework treats $h$ and $t$ as coordinates of an extended information
manifold $(h,t)$. The
geometric observables characterize the speed of
evolution on the
manifold and the
alignment between the temporal and parameter-deformation directions. Correlations between these
geometric quantities and two widely used measures of non-
equilibrium dynamics, the
entanglement entropy and the Loschmidt echo, are analyzed.
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Mesoscale and Nanoscale Physics
Topological charges and parity selection at Floquet quasienergy degeneracies
Sigmund Kohler and David Guéry-Odelin
The quasienergy spectrum of a strongly driven two-level system as a function of the driving parameters exhibits conical intersections, which are enabled by hidden time-nonlocal
symmetries. We show that each such crossing carries a quantized topological charge: the Floquet–Berry phase acquired along an adiabatic loop around a cone is equal to a $\mathbb{Z}_2$-valued charge. We further identify a second family of degeneracies that occurs at vanishing driving amplitude, when the level splitting matches $m$ energy quanta of the field. Along the Stark-shifted resonance line, the minimum quasienergy gap opens as $|A|^m$, and the charge is nontrivial only for odd $m$. We analytically derive both results from a perturbative reduction to a
spin-$1/2$ in an effective two-dimensional
magnetic field and confirm them numerically through the Bargmann invariant. Moreover, we propose a chirality-based protocol that cancels the dynamical phase to isolate the
geometric one, and an ancilla-based Ramsey readout that renders the topological charge directly observable.
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Statistical Mechanics
Kibble–Zurek Mechanism and Defect Freezing in Imbalanced-Pairing Kitaev Models
R. Jafari, Alireza Akbari, Shukhrat Mardonov et al. (+1 more)
We investigate driven dynamics across critical and exceptional points in the one- and two-dimensional imbalanced-pairing Kitaev models using both the wave-function normalization approach and the biorthogonal framework. For a positive pairing imbalance parameter, the quasiparticle spectrum remains real, and a pairing imbalance neither shifts the
equilibrium phase boundaries nor generates imaginary eigenenergies. In this regime, the defect density follows the conventional Kibble–Zurek scaling in one dimension and the extended Kibble–Zurek scaling, arising from a gapless
manifold, in two dimensions within both frameworks. The corresponding scaling exponents are therefore governed by those of the Hermitian transition. For a negative pairing imbalance parameter, time-reversal
symmetry is broken, the quasiparticle spectrum develops complex
eigenvalues, and the gap closes at exceptional points. For ramps ending at an exceptional point, the defect density follows the modified Kibble–Zurek scaling in the wave-function normalization approach, whereas it obeys the conventional Kibble–Zurek scaling in the biorthogonal framework. When the ramp traverses the time-reversal-
symmetry-broken region, a finite density of defects remains even in the adiabatic limit, leading to defect freezing in both frameworks. Although this frozen background indicates a breakdown of adiabaticity, the excess defects generated on top of this background continue to obey the conventional Kibble–Zurek scaling in one dimension and the extended Kibble–Zurek scaling in two dimensions.
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All authors R. Jafari, Alireza Akbari, Shukhrat Mardonov, A. Langari
Superconductivity
Resolving unconventional gap structure in kagome superconductors with hybrid microwave circuits
Yejin Lee, Haolin Jin, Sushmita Chandra et al. (+12 more)
Unconventional superconductivity is a hallmark of exotic
quantum matter, where determining the pairing
symmetry is essential for uncovering its microscopic origin. Kagome
superconductors provide a fertile landscape for emergent phenomena arising from strong electronic correlations and nontrivial band
topology, yet their superconducting pairing
symmetry remains elusive. The superconducting gap structure is commonly probed via electrodynamic response, but such measurements are inapplicable to thin flakes due to their small volume and delicate nature. Superconducting microwave resonators offer a coherent and highly sensitive platform for probing electrodynamic responses, with versatile designs that enable incorporation of diverse materials and geometries. Here, we integrate flakes into microwave
circuits, enabling noninvasive access to the superfluid response through contactless coupling that preserves structural integrity. By engineering the device geometry to suppress parasitic two-level-system losses that dominate dissipation in microwave
circuits, we isolate the intrinsic material response. Remarkably, the temperature-dependent superfluid density exhibits linear behavior at low temperatures, consistent with a nodal gap structure. Our approach establishes a noninvasive platform for probing electrodynamic response of fragile superconducting flakes while advancing hybrid microwave architectures for
quantum technologies.
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All authors Yejin Lee, Haolin Jin, Sushmita Chandra, Berit H. Goodge, Edouard Lesne, Tommaso Confalone, Francesco Tafuri, Davide Massarotti, Golam Haider, Kornelius Nielsch, Bernd Büchner, Claudia Felser, Debanjan Chowdhury, Nicola Poccia, Uri Vool
Materials Science
Weisfeiler-Lehman subtree encoding for Bayesian optimization of atomic configurations
Akira Kusaba, Tatoshi Yonemori, Tetsuji Kuboyama et al. (+1 more)
The efficiency of
Bayesian optimization (BO) of atomic configurations depends strongly on how configurations are encoded. We introduce the Weisfeiler-Lehman (WL) subtree kernel, which views configurations as element-labeled graphs and measures their similarity by how many local structural patterns they share, into
Bayesian-optimization-based configuration search. Because this kernel is reproduced as the plain inner product of explicit features (L$^2$-normalized histograms of local topological patterns), introducing it reduces to introducing the corresponding features: the encoding enters existing BO frameworks as an ordinary descriptor. In a
benchmark ground-state configuration search of cubic BC$_2$N evaluated with a universal machine-learning interatomic potential, the WL encoding reached the ground state almost immediately after a shared random initialization of 100 samples in every one of five independent rounds (108$\pm$5 evaluations on average), whereas the one-hot baseline required 280$\pm$122 evaluations; the WL-driven sampler first exhausted the degenerate ground-state group and then discovered the metastable degenerate groups from the bottom up, in order of increasing energy.
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All authors Akira Kusaba, Tatoshi Yonemori, Tetsuji Kuboyama, Yoshihiro Kangawa
Materials Science
Beyond Panchromatic Absorption: Deciphering the Excited-State Maze from Light Absorption to Photocatalysis in Dye-Sensitized MOFs
Manuela L. Kim, Mauricio E. Calvo, Katsuya Teshima et al. (+2 more)
Metal–organic frameworks (MOFs) are promising photocatalysts whose visible-light absorption can be extended through linker functionalization; however, a red-shifted absorption edge does not guarantee enhanced efficiency. Here, we establish a multi-spectroscopic framework to decipher the photophysical fate of photoexcited states in diazo-sensitized UiO-66 using 2D photoluminescence (PL/PLE) mapping and wavelength-resolved continuous-wave X-band photo-EPR. By correlating visible absorption with photo-EPR and PLE action spectra, we distinguish a productive red shift from a non-productive emissive red shift. In highly active UiO-66-Anisole (97% activity relative to \ch{TiO2}), photo-EPR tracks the new absorption band, confirming that excitation populates a charge-transfer pathway yielding persistent,
spin-separated states. Conversely, poorly active UiO-66-$\beta$-naphthol (4%) exhibits an extended visible absorption tracked by PLE but not photo-EPR. This reflects excitation trapping in a localized state caused by an ortho-$\mathrm{OH}$ group forming a rigid intramolecular hydrogen bond, which locks the keto-hydrazone tautomer and disrupts the conjugated azo bridge. A new optical overlap descriptor ($S_{\mathrm{Exc}}$) quantitatively captures this trade-off across the series. We demonstrate that photosensitizer design must suppress rigid tautomeric traps and target specific charge-transfer
manifolds ($\lambda \le 500$~nm) rather than merely maximizing apparent panchromatic absorption breadth.
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All authors Manuela L. Kim, Mauricio E. Calvo, Katsuya Teshima, Fabio La Mattina, Eugenio H. Otal