Mesoscale and Nanoscale Physics · Cross-listed from physics.optics
Quantum bianisotropy in light-matter interaction
E. O. Kamenetskii
Quantum bianisotropy and chirality are fundamental concepts in light matter interaction that describe how materials with broken
symmetries respond to electromagnetic fields at the level of macroscopic
quantum electrodynamics. In
quantum bianisotropy, magnetoelectric (ME) energy plays a critical role in mediating and enhancing light matter interactions. This concept is essential for bridging the gap between classical electromagnetics (where bianisotropy often involves field nonlocality) and
quantum mechanics in metamaterials. The precise manipulation of a
quantum emitter's properties at a subwavelength scale is due to near fields, which effectively function as a tunable environment. We show that the ME near field, interpreted as a structure combining the effect of bianisotropy (chirality) with a
quantum atmosphere, is a nonMaxwellian field with spacetime
symmetry breaking.
Quantum ME fields arise from the dynamic modulation and topological coupling of magnetization and electric polarization within ME meta atoms, specific subwavelength structural elements with
magnetic and dielectric subsystems in
magnetic insulators.
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Mesoscale and Nanoscale Physics · Cross-listed from quant-ph
Optimal control of a dissipative micromaser quantum battery in the ultrastrong coupling regime
Maristella Crotti, Luca Razzoli, Luigi Giannelli et al. (+2 more)
We investigate the open-system dynamics of a micromaser
quantum battery in the ultrastrong-coupling (USC) regime. The battery consists of a quantized harmonic mode sequentially interacting, via the Rabi
Hamiltonian, with a stream of
qubits acting as chargers. USC enhances the charging speed but also induces unbounded energy growth and highly mixed cavity states. Dissipation suppresses this behavior, driving the system to a steady state with finite energy and ergotropy. Using optimal control theory, we show that the interplay between USC and dissipation enhances both charging performance and long-term stability against losses.
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All authors Maristella Crotti, Luca Razzoli, Luigi Giannelli, Giuseppe A. Falci, Giuliano Benenti
Disordered Systems and Neural Networks
Integral Variable Range Hopping for Modeling Electrical Transport in Disordered Systems
Chenxin Qin, Chenyan Wang, Mouyang Cheng et al. (+1 more)
The variable range hopping (VRH) model has been widely applied to describe electrical transport in disordered systems, providing theoretical formulas to fit temperature-dependent electric conductivity. These models rely on oversimplified assumptions that restrict their applicability and result in problematic fitting behaviors, yet their overusing situation is becoming increasingly serious. In this work we formulate an integral variable range hopping (IVRH) model, which replaces the empirical temperature power-law dependence in standard VRH theories with a physics-inspired integral formulation. The model builds upon the standard hopping probability $\omega(R)$ w.r.t. hopping distance $R$ and incorporates the density of accessible electronic states through an effective volume function $V(R)$, which reflects the influence of system geometry. The IVRH formulation inherently reproduces both the Mott behavior at low temperatures and the Arrhenius behavior at high temperatures, respectively, and enables a smooth transition between the two regimes. We apply the IVRH model to two-dimensional, three-dimensional, and multi-layered systems. Monte Carlo simulations validate the model's predictions and yield consistent values for the fitting parameters, with substantially reduced variances compared to fitting using the standard VRH model. Furthermore, the improved robustness of IVRH also extends to the transport measurements in monolayer MoS$_2$ system and monolayer WS$_2$ system, enabling more physically meaningful interpretation.IVRH model offers a more stable and physically sound framework for interpreting hopping transport in low-dimensional amorphous materials, providing deeper insights into the universal
geometric scaling factors that govern charge transport in disordered systems.
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All authors Chenxin Qin, Chenyan Wang, Mouyang Cheng, Ji Chen
Statistical Mechanics
Random matrix theory universality of current operators in spin-$S$ Heisenberg chains
Mariel Kempa, Markus Kraft, Robin Steinigeweg et al. (+2 more)
Quantum chaotic systems exhibit certain universal statistical properties that closely resemble predictions from random
matrix theory (RMT). With respect to observables, it has recently been conjectured that, when truncated to a sufficiently narrow energy window, their statistical properties can be described by an unitarily invariant ensemble, and testable criteria have been introduced, which are based on the scaling behavior of free cumulants. In this paper, we investigate the
conjecture numerically in translationally invariant Heisenberg
spin chains with
spin quantum number $S =\frac{1}{2},1,\frac{3}{2}$. Combining a
quantum-typicality-based numerical method with the exploitation of the system's
symmetries, we study the
spin current operator and find clear evidence of consistency with the proposed criteria in chaotic cases. Our findings further support the
conjecture of the existence of RMT universality as manifest in the observable properties in
quantum chaotic systems.
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All authors Mariel Kempa, Markus Kraft, Robin Steinigeweg, Jochen Gemmer, Jiaozi Wang
Strongly Correlated Electrons · Cross-listed from quant-ph
Quantitative approach for the Dicke-Ising chain with an effective self-consistent matter Hamiltonian
J. Leibig, M. Hörmann, A. Langheld et al. (+2 more)
In the thermodynamic limit, the Dicke-Ising chain maps exactly onto an effective self-consistent matter
Hamiltonian with the
photon field acting solely as a self-consistent effective field. As a consequence, no
quantum correlations between
photons and
spins are needed to understand the
quantum phase diagram. This enables us to determine the
quantum phase diagram in the thermodynamic limit using numerical linked-cluster expansions combined with density
matrix renormalization group calculations (NLCE+DMRG) to solve the resulting self-consistent matter
Hamiltonian. This includes magnetically ordered phases with significantly improved accuracy compared to previous estimates. For
ferromagnetic Ising couplings, we refine the location of the multicritical point governing the change in the order of the superradiant phase transition, reaching a relative accuracy of $10^{-4}$. For
antiferromagnetic Ising couplings, we confirm the existence of the narrow
antiferromagnetic superradiant phase in the thermodynamic limit. The effective matter
Hamiltonian framework identifies the
antiferromagnetic superradiant phase as the many-body ground state of an
antiferromagnetic transverse-field Ising model with longitudinal field. This phase emerges through continuous Dicke-type polariton condensation from the
antiferromagnetic normal phase, followed by a first-order transition to the paramagnetic superradiant phase. Thus, NLCE+DMRG provides a precise determination of the Dicke-Ising phase diagram in one dimension by solving the self-consistent effective matter
Hamiltonian.
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All authors J. Leibig, M. Hörmann, A. Langheld, A. Schellenberger, K.P. Schmidt
Mesoscale and Nanoscale Physics · Cross-listed from quant-ph
Coherence Limits in Interference-Based cos(2$\varphi$) Qubits
S. Messelot, A. Leblanc, J.-S. Tettekpoe et al. (+4 more)
We investigate the coherence properties of parity-protected $\cos(2\varphi)$
qubits based on interferences between two Josephson elements in a superconducting loop. We show that
qubit implementations of a $\cos(2\varphi)$ potential using a single loop, such as those employing semiconducting junctions, rhombus
circuits, flowermon and KITE structures, can be described by the same
Hamiltonian as two multi-harmonic Josephson junctions in a SQUID geometry. We find that, despite the parity protection arising from the suppression of single Cooper pair tunneling, there exists a fundamental trade-off between charge and flux noise dephasing channels. Using numerical simulations, we examine how relaxation and dephasing rates depend on external flux and
circuit parameters, and we identify the best compromise for maximum coherence. With currently existing
circuit parameters, the
qubit lifetime $T_1$ can exceed milliseconds while the dephasing time $T_\varphi$ remains limited to only a few microseconds due to either flux or charge noise. Our findings establish practical limits on the coherence of this class of
qubits and raise questions about the long-term potential of this approach.
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All authors S. Messelot, A. Leblanc, J.-S. Tettekpoe, F. Lefloch, Q. Ficheux, J. Renard, É. Dumur
Materials Science
Physically Unclonable Functions Based on Single-Walled Carbon Nanotubes: A Scalable and Inexpensive Method toward Unique Identifiers
Enrique Burzurí, Daniel Granados and Emilio M. Pérez
A physically un-clonable function (PUF) is a physical system that cannot be reproduced or predicted and therefore is a good basis to build security and anti-counterfeiting applications. The unclonability of PUFs typically stems from the randmoness induced in a system during sophisticated fabrication methods. It is precisely this built-in complexity the bottleneck hindering scalability and increasing costs. Here, we produce in a simple manner PUFs based on arrays of carbon nanotubes junctions simultaneously assembled by dielectrophoresis. We demonstrate that the intrinsic inhomogeneity of carbon nanotubes at the nanoscale, combined with the unpredictability introduced by
liquid phase-based fabrication methods results in unique electronic profiles of easily scalable devices. This approach could be extrapolated to generate PUFs based on other nanoscale materials
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Superconductivity
Growth and hydrostatic-pressure study of a type-II superconductor Bi$_2$Ta$_3$S$_6$ single crystal
Li Chenglin, Yang Yaling, Yang Zhilong et al. (+9 more)
We report the growth and physical properties of single-crystalline Bi$_2$Ta$_3$S$_6$ crystallizing in $P6_3/mcm$ space group, which comprises alternating Ta-S layers and Bi layers with each Bi atom connected with adjacent S atoms. Temperature-dependent electrical resistivity measurements reveal a superconducting transition at 0.84 K, with upper critical field 231 Oe under an out-of-plane
magnetic field. The magnetization measurements confirm its nature as a type-II
superconductor, with anisotropic Ginzburg-Landau parameter $\kappa_{ab}$ = 7.67 and $\kappa_c$ = 4.50.
Hall measurements indicate the dominant carriers as hole. Hydrostatic pressure is applied, under which both the superconducting transition temperature and upper critical field increase sharply under low pressure before undergoing slight suppression under higher pressure. Density functional theory calculations reveal non-trivial topological surface states on (100) surface in Bi$_2$Ta$_3$S$_6$, which may offer a new avenue for exploring potential topological superconductivity in layered transition metal dichalcogenides.
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All authors Li Chenglin, Yang Yaling, Yang Zhilong, Deng Junze, Zhang Ruihan, Chen Weiwei, Pan Yue, Wang Yulong, Wang Xuhui, Wang Bosen, Wang Zhijun, Wang Gang
Materials Science
Comprehensive Molecular-level Understanding of MgO Hydration through Computational Chemistry
Taichi Inagaki and Miho Hatanaka
The hydration of magnesium
oxide (MgO) to magnesium hydroxide (Mg(OH)$_2$) is a fundamental solid-surface chemical reaction with significant implications for materials science. Yet its molecular-level mechanism from water adsorption to Mg(OH)$_2$ nucleation and growth remains elusive due to its complex and multi-step nature. Here, we elucidate the molecular process of MgO hydration based on structures of the MgO/water interface obtained by a combined computational chemistry approach of potential-scaling molecular dynamics simulations and first-principles calculations without any a priori assumptions about reaction pathways. The result shows that the Mg$^{2+}$ dissolution follows the dissociative water adsorption. We find that this initial dissolution can proceed exothermically even from the defect-free surface with an average activation barrier of $\sim$12 kcal/mol. This exothermicity depends crucially on the stabilization of the resulting surface vacancy, achieved by
proton adsorption onto neighboring surface oxygen atoms. Further Mg$^{2+}$ dissolution then occurs in correlation with
proton penetration into the solid. Moreover, we find that the Mg(OH)$_2$ nucleation and growth proceeds according to the dissolution-precipitation mechanism, rather than a solid-state reaction mechanism involving a direct topotactic transformation. In this process, Mg$^{2+}$ ions migrate away from the surface and form amorphous Mg-OH chains as precursors for Mg(OH)$_2$ nucleation. We also demonstrate that sufficient water facilitates the formation of more ordered crystalline
nuclei. This computational study provides a comprehensive molecular-level understanding of MgO hydration, representing a foundational step toward elucidating the mechanisms of this class of complex and multi-step solid-surface chemical reactions.
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Materials Science
Classification and design of two-dimensional altermagnets
Sike Zeng, Dong Liu, Hongjie Peng et al. (+3 more)
Altermagnets – newly identified collinear antiferromagnets – carry zero net moment with non-relativistic,
spin-polarized bands, distilling the best of ferromagnets and antiferromagnets into a single spintronic platform. Shrunking to the two-dimensional limit, they inherit the tunability of two-dimensional
crystals while adding
symmetry-protected
spin splitting, a combination now driving intense experimental interest. Here, we review the
symmetry classification of two-dimensional altermagnets based on
spin-group theory and survey the growing list of candidate materials, emphasizing those with large
spin splitting for experimental realization. We then examine strategies for engineering two-dimensional altermagnetism. This Review aims to consolidate theoretically proposed candidate materials and realization strategies for two-dimensional altermagnets, providing insights for future experimental efforts in this emerging field.
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All authors Sike Zeng, Dong Liu, Hongjie Peng, Chang-Chun He, Xiao-Bao Yang, Yu-Jun Zhao
Materials Science
Effect of Number of Bilayers on the Anomalous Hall Effect in [Si/Fe]N Multilayers
Sudhansu Sekhar Das and M. Senthil Kumar
The influence of varying the number of
bilayers (N) on the anomalous
Hall effect (AHE) in sputtered Si/Fe multilayers has been investigated. Both the AHE and magnetisation data reveal the in-plane
magnetic anisotropy in the samples. Large enhancement of about 24 times in the saturation anomalous
Hall resistance (R_Ahs) and anomalous
Hall sensitivity (S) has been observed upon decreasing N from 20 to 1. When compared with the bulk Fe, the values of R_Ahs and anomalous
Hall coefficient, Rs obtained for N= 1 were enhanced by about 5 and 3 orders of magnitude, respectively. The Rs follows the longitudinal electrical resistivity Rho as Rs proportional to Rho^2.1, suggesting side jump as the dominant mechanism of the AHE. The S as high as 22 Ohm/T over a wide operational field range of -8 to +8 kOe has been obtained for N = 1.
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Materials Science
A Neuroevolution Potential for Gallium Oxide: Accurate and Efficient Modeling of Polymorphism and Swift Heavy-Ion Irradiation
Yaohui Gu, Binbo Li, Lingyang Jiang et al. (+6 more)
Gallium
oxide (Ga2O3) is a wide-bandgap
semiconductor with promising applications in high-power and high-frequency electronics. However, its complex polymorphic nature poses substantial challenges for fundamental studies, particularly in understanding phase-transformation behaviors under nonequilibrium conditions. Here, we develop a robust, accurate, and computationally efficient machine-learning interatomic potential (MLIP) for Ga2O3 based on the neuroevolution potential (NEP) framework combined with an energy-dependent weighting strategy. The resulting NEP potential demonstrates clear advantages over the state-of-the-art tabGAP potential with respect to both accuracy and computational efficiency. Furthermore, we introduce a physically process-oriented sampling strategy to systematically augment the training
dataset, thereby enhancing the MLIP performance for targeted physical phenomena. As a representative application, a dedicated NEP potential is constructed for swift heavy-ion (SHI) irradiation simulations of e̱ta}-Ga2O3. The simulated results are in quantitative agreement with experimental observations and provide a consistent physical explanation for the reported experimental discrepancies regarding phase transformations in the ion track of e̱ta}-Ga2O3.
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All authors Yaohui Gu, Binbo Li, Lingyang Jiang, Yuhui Hu, Wenqiang Liu, Lijun Xu, Pengfei Zhai, Jie Liu, Jinglai Duan
Strongly Correlated Electrons
Electric field effects in one-dimensional spin-1/2 $K_1J_1\Gamma_1\Gamma_1^\prime K_2J_2$ model with ferromagnetic Kitaev coupling
Wang Yang, Helin Wang and Chao Xu
We perform a systematic study on the effects of electric fields in the Luttinger
liquid phase of the one-dimensional
spin-$1/2$ $K_1J_1\Gamma_1\Gamma_1^\prime K_2J_2$ model in the region of
ferromagnetic nearest-neighboring Kitaev coupling. We find that while electric fields along $(1,1,1)$-direction maintain the Luttinger
liquid behavior, fields along other directions drive the system to a dimerized state. An estimation is made on how effective a $(1,1,1)$-field is for tuning the Luttinger parameter in real materials. Our work is useful for understanding the effects of electric fields in one-dimensional generalized Kitaev
spin models, and provides a starting point for exploring the electric-field-related physics in two dimensions based on a quasi-one-dimensional approach.
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Superconductivity
Microwave Kerr/Faraday Resonance in Two-dimensional Chiral Superconductors
Taiki Matsushita, Jun'ichi Ieda, Yasufumi Araki et al. (+3 more)
We investigate the polar Kerr and Faraday effects in two-dimensional multiband
chiral superconductors. We show that the clapping modes–the relative phase and amplitude oscillations between two
chiral components of the superconducting order parameter–lie well within the quasiparticle excitation gap in multiband systems and dominate these magneto-optical responses in the microwave regime. The Kerr and Faraday rotation angles exhibit the resonant enhancement with sign reversals in the microwave regime as a function of the light frequency, reaching peak values on the order of 100 nrad–10 $\mu$rad in thin films of candidate
chiral superconductors. These resonances are accessible in superconducting atomic layer materials and provide a generic probe of
chiral superconductivity in two-dimensional systems.
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All authors Taiki Matsushita, Jun'ichi Ieda, Yasufumi Araki, Takahiro Morimoto, Ilya Vekhter, Youichi Yanase
Strongly Correlated Electrons
Comparison of SCAN+U and r2SCAN+U for Charge Density Wave Instability and Lattice Dynamics in CuTe
Seungha Ju and Sooran Kim
Identifying an appropriate exchange-correlation functional and computational conditions is essential for explaining the fundamental physics of materials and predicting their properties. Here, we investigate the performance of the meta-GGA functionals SCAN and r2SCAN, with and without a Hubbard U, for describing the charge density wave (CDW) in the quasi-one-dimensional material CuTe. By examining the Te-Te bond modulation,
phonon dispersions, and electronic structures, we identify clear differences in how the two functionals capture the structural and dynamical properties of the CDW formation. r2SCAN+U reproduces the experimentally observed Te-chain distortions in the CDW phase and the
phonon soft mode at qCDW=(0.4, 0.0, 0.5) in the non-CDW phase, whereas SCAN exhibits unphysical
phonon behavior. The atomic displacements of the soft mode agree well with the experimental Te modulation. Despite their similar electronic structures and optimized
lattice constants, our results demonstrate that r2SCAN is a more suitable choice than SCAN for describing CDW formation and
lattice dynamics in CuTe.
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Materials Science
Density of States of Ru3 and Pt3 Clusters Supported on Sputter-Deposited TiO2
Liam Howard-Fabretto, Timothy J. Gorey, Guangjing Li et al. (+4 more)
In this work, 3-atom clusters, Ru3 and Pt3, were deposited onto
radio frequency RF-sputter deposited TiO2, treated with Ar+ ion sputtering. Ru3 was deposited by both solution submersion and chemical vapor deposition of Ru3(CO)12, while Pt3 was deposited under ultra-high
vacuum using a
laser vaporisation cluster source. The valence electronic density of states (DOS) of the deposited clusters were analysed after heat treatment using ultraviolet photoelectron spectroscopy (UPS) and metastable impact electron spectroscopy (MIES), where UPS measures the top several layers while MIES measures only the top atomic layer. XPS was used to determine the cluster surface coverages. The DOS were found to be very similar between Ru3 deposited by solution submersion and chemical vapor deposition. MIES results for Ru3 had contributions from titania O 2p sites due to encapsulation by a reduced titania overlayer. For Pt3 clusters the UPS and MIES results provided evidence that Pt was present on the topmost layer, and encapsulation did not occur. The proposed reason for the encapsulation of Ru3 but not of Pt3 is the higher surface energy of Ru over Pt. It is concluded that Pt clusters deposited onto TiO2 can modify the outermost layer by adding discrete energy levels on the surface, whereas the Ru clusters being encapsulated just below the surface generate a broad distribution of energy states close to the
Fermi level. The outcome of this work is that Pt3-cluster-modified surfaces could be used as catalysts for reactions where the Pt3 energy levels are suitable for the respective reaction. The implication of the DOS found for photocatalytic water splitting are discussed.
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All authors Liam Howard-Fabretto, Timothy J. Gorey, Guangjing Li, Siriluck Tesana, Gregory F. Metha, Scott L. Anderson, Gunther G. Andersson
Materials Science · Cross-listed from cs.CE
A Generalizable Framework for Building Executable Domain-Specific LLMs under Data Scarcity: Demonstration on Semiconductor TCAD Simulation
Di Wang, Zhenhua Wu, Yu Liu et al. (+2 more)
Scientific and engineering verticals often suffer from data scarcity and strict executability requirements: models must generate not only fluent text, but also syntactically valid, tool-compilable scripts. We present a schema-first
alignment framework for building compact, executable domain-specific LLMs in low-resource settings. The framework integrates three core components: (i) large-scale synthetic QA data generation from expert documentation to instill foundational domain knowledge; (ii) a code-centric IR->DPO workflow that converts verified tool decks into interpretable intermediate representations (IR), performs equivalence-preserving diversification, and constructs preference pairs to directly optimize instruction compliance and code executability; and (iii) a controlled evaluation of
Retrieval-Augmented Generation (RAG), showing that while RAG benefits general LLMs, it can marginally degrade the performance of already domain-aligned models. We demonstrate the framework by instantiating TcadGPT for
semiconductor Technology Computer-Aided Design (TCAD). Using 1.5M synthetic QA pairs and an IR-driven DPO
dataset, TcadGPT attains 85.6% semantic accuracy and an 80.0% syntax pass rate on SDE executability tests, substantially outperforming state-of-the-art general LLMs such as GPT-4o. To probe portability beyond TCAD, we apply the same recipe to the open-source FEM solver Elmer, observing consistent improvements in script-level success rates over general-purpose baselines. All
datasets,
benchmarks, and code (including P1, P2, and IR->DPO) are released for reproducibility. Together, these results suggest that the proposed framework provides a robust and reproducible path toward executable LLMs in specialized, data-scarce professional domains.
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All authors Di Wang, Zhenhua Wu, Yu Liu, Kai Chang, Shaohua Wu
Mesoscale and Nanoscale Physics
Electroluminescence in dopant-free GaAs/AlGaAs single heterojunctions: 2D free excitons, H-band, and the tidal effect
N. Sherlekar, S. R. Harrigan, L. Tian et al. (+9 more)
Bright electroluminescence (EL) from dopant-free ambipolar lateral p-n junctions in GaAs/AlGaAs single heterointerface (SH)
heterostructures is used to probe neutral free
excitons arising from two-dimensional electron and hole gases (2DEGs and 2DHGs). The EL spectra reveal both the heavy-hole neutral free
exciton (X$^0$) and the high-energy free
exciton of the H band (HE). A combination of transition energies, lifetimes, spatial emission profiles, and temperature dependences points to a predominantly two-dimensional character for these
excitons at the SH. For X$^0$, the EL peak energies (1515.5-1515.7 meV) lie slightly above the corresponding bulk GaAs photoluminescence (PL) line at 1515.3 meV, while time-resolved measurements yield markedly shorter lifetimes for EL than for PL (337 ps vs. 1610 ps), consistent with recombination in a confined interfacial layer. The HE
exciton exhibits a Stark blueshift under forward bias below threshold, and its energies and lifetimes (down to 575 ps) are tuned by the topgate voltage; above threshold, HE emission is quenched in favor of X$^0$. Finally, the
tidal effect $-$ a form of pulsed EL generated by swapping the topgate voltage polarity in ambipolar field-effect transistors $-$ produces an X$^0$ line at the same energy as in the lateral p-n junction and reproduces the characteristic nonmonotonic frequency dependence of the brightness previously observed in
quantum-well
heterostructures, again indicating a 2D-like origin. Taken together, these results show electrically generated and controllable 2D-like
excitons (HE and X$^0$), thereby bridging 2D
exciton physics and 2DEG/2DHG platforms in dopant-free GaAs/AlGaAs SH devices.
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All authors N. Sherlekar, S. R. Harrigan, L. Tian, B. Cunard, Y. Qi, B. Khromets, M. C. Tam, H. S. Kim, Z. R. Wasilewski, J. Baugh, M. E. Reimer, F. Sfigakis
Mesoscale and Nanoscale Physics
Anomalous transport in quasiperiodic lattices: emergent exceptional points at band edges and log-periodic oscillations
Jinyuan Shang and Haiping Hu
Quasiperiodic systems host exotic transport regimes that are distinct from those found in periodic or disordered
lattices. In this work, we study
quantum transport in the Aubry-André-Harper
lattice in a two-terminal setup coupled to zero-temperature reservoirs, where the conductance is evaluated via the nonequilibrium Green's function method. In the extended phase, we uncover a universal subdiffusive transport when the bath chemical potential aligns with the band edges. Specifically, the typical conductance displays a scaling of $\mathcal{G}_{\text{typ}}\sim L^{-2}$ with system size $L$. We attribute this behavior to the emergence of an exceptional point (Jordan normal form) in the transfer
matrix in the thermodynamic limit. In the localized phase, the conductance shows exponential decay governed by the Lyapunov exponent. Intriguingly, in the critical phase, we identify pronounced log-periodic oscillations of the conductance as a function of system size, arising from the discrete scale invariance inherent to the singular-continuous spectrum. We further extend our analysis to the generalized Aubry-André-Harper model and provide numerical evidence suggesting that the exact mobility edge resides within a finite spectral gap. This results in a counter-intuitive exponential suppression of conductance precisely at the mobility edge. Our work highlights the distinct transport behaviors in quasiperiodic systems and elucidates how they are rigorously dictated by the underlying local spectral structure.
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Soft Condensed Matter · Cross-listed from physics.bio-ph
Collective behavior based on agent-environment interactions
Gaston Briozzo, Gustavo J. Sibona and Fernando Peruani
We present a model of active particles interacting through a dynamic, heterogeneous environment, leading to emergent collective behaviors without direct
agent-to-
agent communication. Expanding the resource-dependent framework introduced in Briozzo et al., 2025, arXiv:2512.08762,
agents perform a persistent random walk combined with chemotaxis, directing toward nutrient-rich patches, whose resources are generated by logistic regrowth. We identify distinct phases of collective organization, ranging from disordered gas-like states to polar traveling waves and nematic independent clusters, depending on the interplay between chemotactic sensitivity and angular noise. The system exhibits spontaneous
symmetry breaking and density waves driven purely by the coupling between population dynamics (birth-death processes) and environmental feedback. Our results bridge active matter physics and movement ecology, demonstrating that complex spatiotemporal patterns can arise without direct interaction between
agents, but solely from the maximization of resource intake in a reactive environment.
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Statistical Mechanics · Cross-listed from q-bio.NC
Macroscopic dynamics of quadratic integrate-and-fire neurons subject to correlated noise
Hui Wang and Chunming Zheng
The presence of correlated noise, arising from a mixture of independent fluctuations and a common noisy input shared across the neural population, is a ubiquitous feature of neural
circuits, yet its impact on collective network dynamics remains poorly understood. We analyze a network of quadratic integrate-and-fire
neurons driven by Gaussian noise with a tunable degree of correlation. Using the cumulant expansion method, we derive a reduced set of effective mean-field equations that accurately describe the
evolution of the population's mean firing rate and membrane potential. Our analysis reveals a counterintuitive phenomenon: increasing the noise correlation strength suppresses the mean network activity, an effect we term correlated-noise-inhibited spiking. Furthermore, within a specific parameter regime, the network exhibits metastability, manifesting itself as spontaneous, noise-driven transitions between distinct high- and low-activity states. These results provide a theoretical framework for reducing the dynamics of complex
stochastic networks and demonstrate how correlated noise can fundamentally regulate macroscopic neural activity, with implications for understanding state transitions in biological systems.
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Mesoscale and Nanoscale Physics
Hybrid superinductance with Al/InAs
Junseok Oh, Ido Levy, Tyler Cowan et al. (+4 more)
We report microwave spectroscopy of Josephson junctions chains made from an epitaxial Al/InAs
heterostructure. The chains exhibit superinductance, with characteristic wave impedance exceeding $R_{Q} = \hbar/(2e)^{2}$. The planar nature of the junctions results in a large
plasma frequency, with no measurable deviations from ideal dispersion up to $12~\mathrm{GHz}$. Internal quality factors decrease sharply with frequency, which we describe with a simple loss model. The possibility of a loss mechanism intrinsic to the
superconductor-
semiconductor junction is considered.
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All authors Junseok Oh, Ido Levy, Tyler Cowan, Jacob Issokson, Archana Kamal, Javad Shabani, Andrew P. Higginbotham
Statistical Mechanics
Rotational Memory Function of SPC/E water
Dilipkumar N. Asthagiri and Dmitry V. Matyushov
Memory effects are essential for dynamics of condensed materials and are responsible for non-exponential relaxation of correlation functions of dynamic variables through the
memory function.
Memory functions of dipole rotations for polar
liquids have never been calculated. We present here calculations of
memory functions for single-dipole rotations and for the overall dipole moment of the sample for SPC/E water. The
memory functions for single-particle and collective dipole dynamics turn out to be nearly identical. This result validates theories of dielectric spectroscopy in terms of single-particle time correlation functions and the connection between the collective and single-particle relaxation times through the Kirkwood factor. The dielectric function in this formalism contains no new dynamic information that does not exist in the single-dipole correlation function. A short
memory time, $\lesssim 1$ fs, justifies the use of rotational
diffusion model to describe dynamics of a single molecular dipole moment in bulk water.
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Superconductivity
Electronic structure theory of H$_{3}$S: Plane-wave-like valence states, density-of-states peak and its guaranteed proximity to the Fermi level
Ryosuke Akashi
Superconductivity in sulfur superhydride H$_{3}$S under extreme pressures has been explained theoretically, but it requires a peaked concentration of the electronic density of states (DOS), which has been found in first-principles calculations. The mechanism of this peak formation, though vital for its high transition temperature, has however remained obscure. We address this problem through detailed analysis of the first-principles electronic wave functions. The valence wave functions are shown to be significantly plane-wave-like. From the
Fourier-mode analysis of the self-consistent potential and atomic pseudopotentials, we extract the nearly uniform models that accurately reproduce the first-principles band structure with very few parameters. The DOS peak is shown to be the consequence of the hybridization of specific plane waves. Adjacency of Jones' large zone to the plane-wave spherical
Fermi surface is posited to be the root cause of the multiple plane-wave hybridization, the DOS peak formation and its proximity to the
Fermi level. The present theory resolves the minimal modeling problem of electronic states in H$_{3}$S, as well as establishes a mechanism that may help to boost the transition temperatures in pressure induced
superconductors.
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Mesoscale and Nanoscale Physics
Weyl magnetoplasma waves in magnetic Weyl semimetals
Yuanzhao Wang, Oleg V. Kotov and Dmitry K. Efimkin
Weyl degeneracies in spectra of magnetoplasma waves enable nonreciprocal energy flow and topologically protected modes, yet conventional materials require impractical
magnetic fields to operate. Developing an effective
Hamiltonian framework for
magnetic Weyl semimetals, we show that these systems overcome the limit, hosting Weyl magnetoplasma physics at zero field due to their
giant intrinsic anomalous
Hall response. The resulting
topology supports nonreciprocal modes localized at
magnetic domain walls, including a pair of topological "
Fermi-arc-like modes and additional bound states. These effects are fully developed across a broad THz window, and we propose feasible experimental routes for their detection.
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Mesoscale and Nanoscale Physics · Cross-listed from quant-ph
Reentrant topological phases and entanglement scalings in moiré-modulated extended Su-Schrieffer-Heeger Model
Guo-Qing Zhang, L. F. Quezada and Shi-Hai Dong
Recent studies of moiré physics have unveiled a wealth of opportunities for significantly advancing the field of
quantum phase transitions. However, properties of reentrant phase transitions driven by moiré strength are poorly understood. Here, we investigate the reentrant sequence of phase transitions and the invariant of universality class in moiré-modulated extended Su-Schrieffer-Heeger (SSH) model. For the simplified case with intercell hopping $w=0$, we analytically derive renormalization relations of
Hamiltonian parameters to explain the reentrant phenomenon. For the general case, numerical phase boundaries are calculated in the thermodynamic limit. The bulk boundary correspondence between zero-energy edge modes and
entanglement spectrum is revealed from the degeneracy of both quantities. We also address the correspondence between the central charge obtained from
entanglement entropy and the change in winding number during the phase transition. Our results shed light on the understanding of universal characteristics and bulk-boundary correspondence for moiré induced reentrant phase transitions in 1D condensed-matter systems.
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Materials Science
Performance of AI agents based on reasoning language models on ALD process optimization tasks
Angel Yanguas-Gil
In this work we explore the performance and behavior of
reasoning large
language models to autonomously optimize atomic layer deposition (ALD) processes. In the ALD process optimization task, an
agent built on top of a
reasoning LLM has to find optimal dose times for an ALD precursor and a coreactant without any prior knowledge on the process, including whether it is actually self-limited. The
agent is meant to interact iteratively with an ALD reactor in a fully unsupervised way. We evaluate this
agent using a simple model of an ALD tool that incorporates ALD processes with different self-limited surface reaction pathways as well as a non self-limited component. Our results show that
agents based on
reasoning models like OpenAI's o3 and GPT5 consistently succeeded at completing this optimization task. However, we observed significant run-to-run variability due to the non deterministic nature of the model's response. In order to understand the logic followed by the
reasoning model, the
agent uses a two step process in which the model first generates an open response detailing the
reasoning process. This response is then transformed into a structured output. An analysis of these
reasoning traces showed that the logic of the model was sound and that its
reasoning was based on the notions of self-limited process and saturation expected in the case of ALD. However, the
agent can sometimes be misled by its own prior choices when exploring the optimization space.
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Materials Science
Altermagnetic Signatures and Topological Textures in Ultrathin Multiferroic BiFeO$_3$
Geo Fratian, Maya Ramesh, Xinyan Li et al. (+32 more)
Magnetoelectric multiferroics promise low-power switching, nonvolatile
memory, and signal transduction, yet practical deployment requires ultrathin films where polar and
magnetic order often degrade. Uncompensated bound charge drives depolarization in ferroelectrics, while off-stoichiometry, reduced anisotropy, and charge transfer can produce
magnetic dead layers. Here, we realize a multiferroic phase of BiFeO$_3$ with no dead layer, revealing signatures of emergent altermagnetism in the ultrathin limit. First-principles calculations,
symmetry analysis, atomic-resolution imaging, and
magnetic imaging show that short-
circuit electrostatic boundary conditions and epitaxial strain drive a continuous, thickness-induced phase transition accompanied by multiferroic topological textures. At four unit
cells, these boundary conditions stabilize a collinear monoclinic phase with d-wave altermagnetic order, supported by
magnetic circular dichroism and
spin-resolved photoemission measurements. These results establish a pathway to stabilize unconventional multiferroicity at device-relevant thicknesses, reframing scaling limits for
oxide electronics.
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All authors Geo Fratian, Maya Ramesh, Xinyan Li, Evangelos Golias, Yousra Nahas, Sebastian Maria Ulrich Schultheis, Julian Skolaut, Marti Checa, Arundhati Ghosal, Evan Krysko, Paul Malinowski, Brendan D. Faeth, Jan Priessnitz, F. C. Fobasso Mbognou, Atsushi Hariki, Kosuke Sakurai, Mizuki Furo, Shashank Kumar Ojha, Morgan Congdon, Shiyu Zhou, Alexander Qualls, Kai Litzius, Christoph Klewe, Peter Meisenheimer, Jan Kunes, Kyle Shen, Laurent Bellaiche, Libor Šmejkal, Darrell G. Schlom, Yimo Han, Sergei Prokhorenko, Ramamoorthy Ramesh, Paul Stevenson, Angela Wittmann, Lucas Caretta
Superconductivity · Cross-listed from physics.app-ph
Yerzhan Mustafa and Selçuk Köse
Interface
circuits are the key components that enable the hybrid integration of
superconductor and
semiconductor digital electronics. The design requirements of
superconductor-
semiconductor interface
circuits vary depending on the application, such as high-performance classical computing, superconducting
quantum computing, and digital signal processing. In this survey, various interface
circuits are categorized based on the working principle and structure. The superconducting output drivers are explored, which are capable of converting and amplifying, e.g., single flux
quantum (SFQ) voltage pulses, to voltage levels that
semiconductor circuits can process. Several trade-offs between
circuit- and system-level design parameters are examined. Accordingly, parameters such as the data rate, output voltage, power dissipation, layout area, thermal/heat load of cryogenic cables, and bit-error rate are considered.
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Statistical Mechanics
Stochastic systems with Bose-Hubbard interactions: Effects of bias on particles on a random comb
Swastik Majumder and Mustansir Barma
We study
stochastic transport of interacting particles on a disordered network described by the random comb geometry. The model is defined on a one-dimensional backbone from which branches of random lengths emanate, providing a minimal model of percolation networks beyond the critical percolation probability. The dynamics obeys local detailed balance with respect to a Bose-Hubbard
Hamiltonian containing both an external bias and on-site repulsion. This choice yields an analytically tractable steady state through a mapping to the zero-range-process. We compute the backbone current, branch density profiles, and macroscopic drift velocity, and analyze how bias and interactions compete to shape transport. The backbone current increases monotonically with density, while the drift velocity displays a non-monotonic dependence on the external field, remaining finite for any nonzero bias, in contrast to the vanishing drift velocity of noninteracting particles beyond a threshold bias. Density profiles along branches exhibit stepwise plateaus governed by the ratio of interaction to bias energy. These results highlight how repulsive interactions suppress trapping and restore transport in disordered geometries, bridging earlier studies of field induced drift in random networks with the physics of disordered Bose-Hubbard systems.
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