Disordered Systems and Neural Networks
Analysis and Prediction of Dark Current Mechanisms in Si:P Blocked Impurity Band (BIB) Infrared Detectors
Mengyang Cui, Hongxing Qi, Chengduo Hu et al. (+1 more)
We investigated the nonlinear phenomena observed in the dark current of BIB (blocked-
impurity-band) infrared detectors, including negative differential resistance (NDR) and current oscillations. Our analysis systematically elucidated the intrinsic transport mechanisms in optimized devices, revealing that these anomalies arise from current path clustering induced by structural disorder and
impurity band conduction dynamics. Notably, the simulated current-voltage (I-V) characteristics demonstrated strong agreement with experimental measurements across a wide bias range, confirming the validity of our proposed physical model.Furthermore, we developed a
transformer-based predictive model using experimental dark current
datasets. The model achieved robust performance metrics and this framework enables rapid prediction of dark current trends under varying operational conditions, providing actionable insights for detector optimization.
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All authors Mengyang Cui, Hongxing Qi, Chengduo Hu, Qing Li
Mesoscale and Nanoscale Physics
Momentum-resolved spectroscopy of superconductivity with the quantum twisting microscope
Yuval Waschitz, Ady Stern and Yuval Oreg
We develop a theoretical framework for probing superconductivity with momentum resolution using the
quantum twisting microscope (QTM), a planar tunneling device where a
graphene tip is rotated relative to a two-dimensional sample. Because of in-plane momentum conservation, the QTM directly measures the superconducting spectral function along well-defined trajectories in momentum space. The relative intensities of electron and hole excitations encode the Bogoliubov coherence factors, revealing the momentum dependence of the pairing magnitude. Three $C_{3z}$-related tunneling channels enable direct detection of rotational
symmetry breaking, as well as nodal points in the superconducting order parameter. We apply our framework to superconductivity within the Bistritzer-MacDonald model of noninteracting electrons and the topological heavy-
fermion model, which accounts for electron-electron interactions. Together, these capabilities establish the QTM as a direct probe of the pairing
symmetry and microscopic origin of superconductivity in two-dimensional materials.
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Strongly Correlated Electrons
Evidence for a field-induced Lifshitz transition in the Weyl semimetal CeAlSi
M. M. Piva, T. Helm, J. C. Souza et al. (+4 more)
The Weyl semimetal CeAlSi crystallises in the noncentrosymmetric tetragonal space group $I4_1md$ and exhibits
ferromagnetic order below 8 K, thereby breaking both spatial inversion and time-reversal
symmetries. This unique combination of properties establishes CeAlSi as a model system for studying the interplay between non-trivial topological states and strong electron correlations. In this work, we report observations of Shubnikov-de Haas oscillations in the electrical resistivity under
magnetic fields up to 68 T applied parallel to the [001] crystallographic axis. Our measurements reveal an abrupt change in the oscillation frequencies near 14 T, which is indicative of a field-induced Lifshitz transition. Additionally, our results are consistent with the
ferromagnetic order bringing the Weyl nodes closer to the
Fermi level in CeAlSi. Furthermore, they suggest that the RKKY interaction plays an important role.
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All authors M. M. Piva, T. Helm, J. C. Souza, K. R. Pakuszewski, C. Adriano, P. G. Pagliuso, M. Nicklas
Mesoscale and Nanoscale Physics · Cross-listed from physics.optics
Coupled electric dipole model for a Su-Schrieffer-Heeger chain of optically resonant coreshell nanoparticles
Álvaro Buendía and Nuno M.R. Peres
Coreshell nanoparticles can combine optical features of different materials in a single nanostructure, which makes them interesting for many applications from biomedicine to energy harvesting. On the other hand, periodic arrays of plasmonic nanoparticles can exhibit topological phenomena such as topological edge states. Here we study periodic chains of Si@Ag coreshell nanoparticles. For this task, we combine the hybridization of surface plasmonic modes in complex nanostructures with the coupled electric dipole formalism employed for modelling the scattering of light by periodic arrays of small plasmonic nanoparticles. We propose treating coreshell nanoparticle as several coupled electric dipoles instead of just one and show how this is a more appropriate framework to study arrays of coreshell nanoparticles, which allows to build a one-to-one connection between the resonant modes of the nanoparticles and the dispersion bands of the system. Within this formalism, we show that a Su-Schrieffer-Heeger (SSH) chain of coreshell Si@Ag nanoparticles host multiple topological edge states pinned at the resonant frequencies of the coreshell nanoparticles.
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Strongly Correlated Electrons
First-order phase transition driven by competing charge-order fluctuations in 1T'-TaTe$_{2}$
S. K. Mahatha, A. Kar, J. Corral-Sertal et al. (+20 more)
First-order phase transitions, characterized by a discontinuous change in the order parameter, are intriguing phenomena in condensed matter physics. However, the underlying, material-specific, microscopic mechanisms often remain unclear. Here, we unveil a high-temperature incommensurate charge-order precursor with the wave vector $\mathbf{q}^* = (0, \frac{1}{4}+\delta, \frac{1}{2})$ in the 1T' phase of TaTe$_2$, which competes with fluctuating high-temperature Ta trimer bonding states at $\mathbf{q}_\mathrm{CO} =(0, \frac{1}{3}, 0)$. The precursor state follows the temperature dependence of the hidden incommensurability of the $\textit{quasi}$-1D nested
Fermi surface. In contrast, the low-temperature commensurate charge order at $\mathbf{q}_\mathrm{CO}$, characterized by a charge disproportionation of the inequivalent Ta sites, appears to be driven by local chemical bonding. Dynamical
lattice calculations identify an imaginary optical mode at $\mathbf{q}^*$, involving an in-plane vibration of the Ta atoms forming a chain-like structure that renormalizes below $T_\mathrm{CO}$. Our experimental and theoretical observations suggest that the controversial first-order phase transition, as captured by phenomenological Ginzburg-Landau theory, results from the competition between two order parameters: one involving
Fermi surface nesting and the other involving local chemical bonding.
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All authors S. K. Mahatha, A. Kar, J. Corral-Sertal, Josu Diego, A. Korshunov, C.-Y. Lim, F. K. Diekmann, D. Subires, J. Phillips, T. Kim, D. Ishikawa, G. Marini, I. Vobornik, Ion Errea, S. Rohlf, M. Kalläne, V. Bellini, A. Q. R. Baron, Adolfo O. Fumega, A. Bosak, V. Pardo, K. Rossnagel, S. Blanco-Canosa
Statistical Mechanics
Stochastic gyration driven by dichotomous noises
Timothée Herbeau, Leonid Pastur, Pascal Viot et al. (+1 more)
We consider
stochastic dynamics of a particle on a plane in presence of two noises and a confining
parabolic potential - an analog of the experimentally-relevant Brownian Gyrator (BG) model. In contrast to the standard BG model, we suppose here that the time-
evolution of the position components is driven not by Gaussian white-noises, but by two statistically-independent dichotomous noises. We calculate analytically the position variances and cross-correlations, as well as the mean angular momentum, which permits us to establish the conditions in which a spontaneous rotational motion of the particle around the origin takes place. We also present a numerical analysis of the mean angular velocity. Lastly, we calculate analytically some marginal position probability density functions revealing a remarkably rich behavior that emerges in such a system of two coupled linear
stochastic differential equations. We show that depending on the values of parameters characterizing noises these distributions approach the steady-state forms defined on a finite support, having very unusual shapes, possessing multiple maxima and minima, plateaus and exhibiting a discontinuous behavior.
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All authors Timothée Herbeau, Leonid Pastur, Pascal Viot, Gleb Oshanin
Strongly Correlated Electrons · Cross-listed from quant-ph
Yang-Lee edge singularity and quantum criticality in non-Hermitian PXP model
Wen-Yi Zhang, Meng-Yun Mao, Qing-Min Hu et al. (+3 more)
We present a comprehensive theoretical framework for
quantum criticality in the non-Hermitian detuned PXP model, and establish the complete phase diagram, which had remained elusive in previous studies. Starting from a numerically identified phase transition point, we construct an exact second-order phase transition boundary through a similarity transformation in the real-energy regime. By introducing the biorthogonal
entanglement entropy and biorthogonal Loschmidt echo, we demonstrate from both
equilibrium and nonequilibrium perspectives that this transition belongs to the Ising universality class. Using the correlation function, we further distinguish between confined and deconfined phases within the $\mathcal{PT}$-symmetric region. In the complex-energy regime, we identify both a full $\mathcal{PT}$ transition and a first-excited-state $\mathcal{PT}$ transition, respectively. Moreover, we identify the location of the Yang-Lee edge singularity (YLES) using both the associated-biorthogonal and self-normal Loschmidt echoes, and extract the corresponding critical exponent, which agrees with the predictions of non-
unitary conformal field theory. Finally, we propose an experimental scheme to observe the YLES in Rydberg atomic arrays, which offers a promising route to exploring non-Hermitian critical phenomena and singularities in future experimental settings.
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All authors Wen-Yi Zhang, Meng-Yun Mao, Qing-Min Hu, Xinzhi Zhao, Gaoyong Sun, Wen-Long You
Mesoscale and Nanoscale Physics
Statistical Structure of Charge Disorder in Si/SiGe Quantum Dots
Saeed Samadi, Łukasz Cywiński and Jan A. Krzywda
Properties of
quantum dot based
spin qubits have significant inter-device variability due to unavoidable presence of various types of disorder in
semiconductor nanostructures. A significant source of this variability is charge disorder at the
semiconductor-
oxide interface, which causes unpredictable, yet, as we show here, correlated fluctuations in such essential properties of
quantum dots like their mutual tunnel couplings, and electronic confinement energies. This study presents a systematic approach to characterize and mitigate the effects of such disorder. We utilize finite element modeling of a Si/SiGe double
quantum dot to generate a large statistical ensemble of devices, simulating the impact of trapped interface charges. This work results in a predictive statistical model capable of generating realistic artificial data for training machine learning
algorithms. By applying Principal Component Analysis to this
dataset, we identify the dominant modes through which disorder affects the multi-dimensional parameter space of the device. Our findings show that the parameter variations are not arbitrary, but are concentrated along a few principal axes, i.e. there are significant correlations between many properties of the devices. We finally compare that against control modes generated by sweeping the gate voltages, revealing limitations of the plunger-only control. This work provides a framework for enhancing the controllability and operational yield of
spin qubit devices, by systematically addressing the nature of electrostatic disorder that leads to statistical correlations in properties of double
quantum dots.
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Statistical Mechanics · Cross-listed from quant-ph
Noise-stabilized discrete time crystals on digital quantum processors
Kazuya Shinjo, Kazuhiro Seki and Seiji Yunoki
Floquet many-body phases such as discrete time
crystals (DTCs) are typically fragile to imperfections, and stabilizing them on noisy
quantum hardware remains a central challenge in nonequilibrium
quantum physics. Here, we use IBM Eagle and Heron superconducting processors to implement Floquet dynamics of a kicked Ising model on two-dimensional Kagome
lattices, engineered via ancilla-assisted
embeddings into the heavy-hex connectivity of the devices. By combining error-mitigated measurements on
quantum hardware with
matrix-product-state simulations incorporating an ancilla-noise model constructed from experimental device data, we observe long-lived subharmonic magnetization oscillations that are stabilized – rather than destroyed – by structured
quantum noise. Across different two-dimensional
lattice geometries, increasing cases beyond Kagome
lattices, and with or without boundary
symmetry-charge pumping, ancilla errors effectively act as spatiotemporal disorder that induces
stochastic sign flips of the Ising couplings, providing a unified mechanism for robust period-doubling responses. When
symmetry-charge pumping is present, intrinsic boundary-localized $\pi$ modes cooperate with this disorder to yield a boundary-assisted DTC characterized by suppressed scrambling and sharply localized dynamics. In contrast, in implementations without pumping, the noiseless dynamics rapidly thermalize and exhibit no subharmonic order, whereas the same noise process alone generates a DTC-like long-lived subharmonic response over experimentally accessible time windows. These results identify engineered ancilla noise as a practical control knob for inducing, stabilizing, and geometrically tailoring nonequilibrium dynamical order on scalable superconducting
quantum processors.
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Statistical Mechanics
Quasi-adiabatic thermal ensemble preparation in the thermodynamic limit
Tatsuhiko Shirai
We investigate a quasi-adiabatic thermal process for preparing finite-temperature ensembles in the thermodynamic limit. The process gradually transforms a thermal ensemble of a noninteracting system into that of an interacting system of interest over a finite operation time, with the temperature controlled by parameters associated with the
entropy of the initial state. We analyze this process in both nonintegrable and integrable
spin chains with translational invariance. For the nonintegrable case, numerical simulations combined with a thermodynamic argument indicate that the thermal properties of local observables are accurately reproduced with a single parameter, although the operation time increases exponentially with precision. In contrast, for the integrable transverse-field Ising model, we analytically show that an extensive number of parameters tied to local conserved quantities is generally necessary, and the performance is affected by the presence of a
quantum phase transition. These results clarify the potential and limitations of the quasi-adiabatic thermal process for an ensemble preparation and highlight the role of integrability in determining its efficiency.
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Materials Science
Ultrafast exciton polaron dynamics in 2D Ruddlesden Popper lead halide perovskites
Anirban Mondal, Kwang Jin Lee, Seungmin Lee et al. (+5 more)
Two dimensional Ruddlesden Popper (2D) RP hybrid perovskites exhibit substantially higher chemical and structural stability than their three dimensional (3D) counterparts, positioning them as promising candidates for next generation optoelectronics. While quasiparticle dynamics in 3D perovskites are well studied, their 2D analogues remain comparatively underexplored. Here we systematically investigate the branching, dynamics, and interactions of free
excitons (FEs) and
exciton polarons EPs in monolayer 2D RP perovskites using visible range femtosecond transient absorption TA spectroscopy. We prepared monolayer 2D RP perovskite thin films with varied organic spacers and distinct fabrication routes for comparative analysis. We find that the EP binding energy is 50 65 meV in (BA)2PbI4 and 37 39 meV in (PEA)2PbI4, consistent with spacer layer dependent coupling as corroborated by FTIR. We reveal a dynamic
equilibrium between FEs and EPs that persists for tens of picoseconds. Notably, the TA signatures differ by fabrication route films from the newly developed process show weaker Auger annihilation and a reduced hot
phonon bottleneck than those from the conventional route trends consistent with fewer traps and
impurities in the former. Coupled rate equation modeling reproduces the transients and quantifies the processes of hot carrier relaxation,
exciton exciton annihilation,
exciton phonon coupling, and FE EP interconversion. These results demonstrate that the chemical synthetic process (fabrication route) and spacer choice significantly influence EP stability and population balance, offering practical levers for engineering ultrafast photophysics in 2D perovskites and guiding the design of advanced optoelectronic devices.
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All authors Anirban Mondal, Kwang Jin Lee, Seungmin Lee, Oui Jin Oh, Myeongsam Jen, Jun Hong Noh, Jong Min Lim, Minhaeng Cho
Materials Science
Unraveling the Corrosion Mechanism of Boro-Alumino-Phospho-Silicate Glass: Advanced Insights from Solid-State NMR Spectroscopy
Muhammad Amer Khan, Lili Hu, Shubin Chen et al. (+2 more)
Corrosion mechanism of minerals and glass is a critical study domain in geology and materials science, vital for comprehending material durability under various environmental conditions. Despite decades of extensive study, a core aspect of these mechanisms - specifically, the formation of amorphous alteration layers upon exposure to aqueous environments - remains controversial. In this study, the corrosion behavior of a boro-alumino-phospho-silicate glass (BAPS) was investigated using advanced solid-state
nuclear magnetic resonance (SSNMR) and SEM techniques. The results reveal a uniform nanoscale phase separation into Al-P-rich and Al-Si-rich domains. During corrosion, the Al-P-rich domain undergoes gelation, whereas the Al-Si-rich domain remains vitreous, forming a gel layer comprised of both phases. Although SEM images show a sharp gel/glass interface - suggestive of a dissolution-precipitation mechanism - the phase coexistence within the gel layer provides definitive evidence against such a mechanism. Instead, we propose an in situ transformation mechanism governed by chemical reactions, involving: (i) preferential hydrolysis of Al-P-rich domain leading to porous gel regions; (ii) retention of Al-Si glass domains within the gel layer, with water infiltrating inter-network spaces; and (iii) selective leaching of phosphorus over aluminum, leading to reorganization of the gel network.
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All authors Muhammad Amer Khan, Lili Hu, Shubin Chen, Yongchun Xu, Jinjun Ren
Strongly Correlated Electrons
Interplay of magnetic and thermodynamic responses in the kagome-triangular system
Zixuan Jia, Lufeng Zhang, Qingzhuo Duan et al. (+5 more)
Inspired by the recent experimental progress in pyrochlore derivative RE$_3$Sb$_3$A$_2$O$_{14}$ (A = Mg, Zn), we investigate the Hubbard model on the kagome
lattice with an additional hopping $t'/t$, which enables continuous interpolation between the kagome and triangular
lattices by using determinant
quantum Monte Carlo simulations. We find that increasing $t'/t$ suppresses the nearest-neighbor
antiferromagnetic correlations. Concurrently, the next-nearest-neighbor
antiferromagnetic correlations are enhanced and closely associated with the emergence of a pronounced low-temperature peak in the specific heat. Increasing on-site interaction $U$ enhances
magnetic correlations and shifts the associated $t'/t$ crossover points to larger values. We also discuss the sign problem to clarify which parameter region of our numerical simulations is accessible and reliable. Our results uncover the competition between frustration and correlations and the interplay of
magnetic and thermodynamic responses in the kagome
lattice, providing insights into correlated states in frustrated materials.
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All authors Zixuan Jia, Lufeng Zhang, Qingzhuo Duan, Zenghui Fan, Jingyao Wang, Ying Liang, Bing Huang, Tianxing Ma
Soft Condensed Matter
Magnetomechanical Coupling in Ferronematic Phases: Influence of Spindle-Shaped Nanodopants on Liquid Crystalline Order
Karin Koch, Joachim Landers, Damian Günzing et al. (+4 more)
Ferronematic phases, composed of
liquid crystals doped with
magnetic nanoparticles, exhibit unique magnetomechanical coupling effects that are of interest for responsive materials. In this study, we investigate the influence of spindle-shaped {\alpha}-Fe_2O_3 nanoparticles functionalized with a mesogen-decorated
polymer brush on the phase behavior and field-induced transitions of a nematic host (5CB). Differential scanning calorimetry (DSC), refractometry, and dielectric spectroscopy reveal a non-monotonic dependence of the nematic-isotropic transition temperature on particle concentration, indicating a competition between stabilizing and destabilizing effects. The order parameter increases with increasing nanoparticle content, in contrast to non-
magnetic reference systems, suggesting an
alignment effect induced by the
magnetic rather than the
geometric anisotropy axis of the dopants. Capacitance measurements of the Freedericksz transition show a pronounced shift in threshold fields, with a critical concentration marking a transition to enhanced
magnetic responsiveness. Additional information on nanospindle
diffusion correlated to the direction-dependent flow of the nematic host was inferred from comparison of Moessbauer spectroscopy and rheology data. Our findings provide insights into the interplay of
magnetic and
geometric anisotropy in ferronematic systems and highlight their potential for applications in tunable soft matter devices.
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All authors Karin Koch, Joachim Landers, Damian Günzing, Hajnalka Nádasi, Heiko Wende, Alexey Eremin, Annette M. Schmidt
Mesoscale and Nanoscale Physics
Buckling and flat bands in twisted bilayer graphene
Jannes van Poppelen and Annica M. Black-Schaffer
Magic-angle twisted
bilayer graphene (TBG) with its flat bands provides a rich platform for exploring emergent electronic orders. Similarly, periodically buckled monolayer
graphene has been proposed as a tunable alternative for realizing flat bands. Here, we investigate the combined effect of buckling and twisting in
bilayer graphene. We find that periodic buckling in large-angle TBG initially enhances band flattening compared to monolayer
graphene, but for sufficiently strong buckling, it instead increases the band dispersion. This occurs both because of the presence of interlayer coupling, which reduces the in-plane kinetic energy, and due to the opening of a gap at the Dirac point resulting from inversion-
symmetry breaking. Additionally, we find that buckling-induced band flattening competes with twist-induced band flattening. While the former breaks sublattice
symmetry, generating a sublattice polarization, the latter prefers to preserve it. This prevents buckling from generating even flatter bands at the magic angle. Nevertheless, we find that buckled TBG can exhibit flatter bands than pristine TBG over a wide range of twist angles, with a flatness similar to that of pristine magic-angle TBG.
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Mesoscale and Nanoscale Physics
Magnetically controllable nonlinear valley Hall effect in centrosymmetric ferromagnets
Ruijing Fang, Jie Zhang, Zhichao Zhou et al. (+1 more)
Valley
Hall effect is fundamental to valleytronics and provides a promising avenue for advancing information technology. While conventional valley
Hall effect requires the inversion
symmetry breaking, the recently proposed nonlinear valley
Hall (NVH) effect removes the
symmetry constraint, and broaden material choices. However, existing studies are limited to nonmagnetic materials without
spin involvement and rely on external strain to break rotational
symmetry. Here, to address these limitations, we design a magnetically controllable NVH effect in centrosymmetric ferromagnets, by the tight-binding model and first-principles calculations. The model calculations demonstrate nonvanishing NVH conductivities can emerge in pristine hexagonal
lattice without external strain, with the magnitude, sign, and
spin polarization of the conductivities being all dependent on the magnetization orientation. The effect thus generates various
spin-polarized valley
Hall currents, characterized by distinct combinations of current direction and
spin polarization. First-principle results on a
ferromagnetic VSi$_2$N$_4$
bilayer confirm considerable NVH conductivities and their dependence on the magnetization. The magnetically controllable NVH effect unlocks the potential of centrosymmetric magnets for valleytronics, and offer opportunities for novel spintronic and valleytronic devices.
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All authors Ruijing Fang, Jie Zhang, Zhichao Zhou, Xiao Li
Statistical Mechanics
Nonequilibrium steady states in bead-spring models: Entropy production and probability distributions
Jetin E Thomas and Ramandeep S. Johal
We study non-
equilibrium models comprising of beads connected by springs. The system is coupled to two thermal baths kept at different temperatures. We derive the steady state probability distributions of positions of the bead for the one-bead system in the underdamped case. We employ the recently proposed technique of an effective temperature, along with numerical simulations to solve the Langevin equations and obtain their corresponding probability distributions. It is observed that the marginal probability distributions in the position are independent of mass. We also obtain theoretically and numerically the rate of
entropy production for the one-bead system. The probability distribution of the positions in the two-beads system are obtained theoretically and numerically, both in the underdamped and overdamped case. Lastly, we discuss the notion of ergodicity and have tested the convergence of the time-averaging and the ensemble-averaging protocols.
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Disordered Systems and Neural Networks · Cross-listed from physics.comp-ph
GO-Diff: Data-free and amortized global structure optimization
Nikolaj Rønne, Tejs Vegge and Arghya Bhowmik
We introduce GO-Diff, a
diffusion-based method for global structure optimization that learns to directly sample low-energy atomic configurations without requiring prior data or explicit relaxation. GO-Diff is trained from scratch using a Boltzmann-weighted score-matching loss, leveraging only the known energy function to guide generation toward thermodynamically favorable regions. The method operates in a two-stage loop of self-sampling and model refinement, progressively improving its ability to target low-energy structures. Compared to traditional optimization pipelines, GO-Diff achieves competitive results with significantly fewer energy evaluations. Moreover, by reusing pretrained models across related systems, GO-Diff supports amortized optimization - enabling faster convergence on new tasks without retraining from scratch.
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Materials Science
Computational Insights into Defect Induced Modulation in Electronic Properties of 2D Nitride Monolayers
Shreya G. Sarkar, Kuneh Parag Shah and Brahmananda Chakraborty
Two-dimensional (2D) nitride materials such as hexagonal boron nitride (h-BN), graphitic carbon nitride (g-C$_3$N$_4$), and beryllonitrene (BeN$_4$) have emerged as promising candidates for next generation electronic, optoelectronic, and energy applications due to their unique structural and electronic properties. This study presents a systematic investigation of the effects of vacancy defect, specifically the role of nitrogen and constituent atom vacancies on the electronic properties of these materials. Our findings reveal that the introduction of nitrogen vacancies significantly alters the electronic characteristics of these materials. In h-BN, the presence of a nitrogen monovacancy significantly lowers the work function from 5.97 eV to 3.45 eV, one of the lowest values reported for any 2D material. Additionally, this defect reduces the band gap from 4.6 eV to 0.64 eV, driving the material toward half-metallic behavior. This is accompanied by the emergence of flat bands near the
Fermi level, indicative of strong electron-electron interactions. In g-C$_3$N$_4$, nitrogen vacancies lead to a decrease in work function and band gap, with double nitrogen vacancies rendering the material nearly metallic. In BeN$_4$, nitrogen vacancies result in minimal charge redistribution and a slight increase in work function, highlighting the material's unique electronic behavior. These results underscore the potential of vacancy engineering in tuning the electronic properties of 2D nitride materials, offering avenues for the design of materials with tailored work functions and band gaps for applications in optoelectronics, spintronics, and catalysis.
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Materials Science
Integration of imprint-free and low coercivity ferroelectric BaTiO3 thin films on silicon
Jingtian Zhao, Beatriz Noheda and Martin F. Sarott
Highly-crystalline ferroelectric
oxides integrated on Si hold great promise for energy-efficient
memory and logic technologies. Exploiting epitaxial strain engineering in these materials is, however, severely hampered on Si, where the large structural mismatch often results in an inferior interfacial quality and causes a degradation of the ferroelectric switching characteristics. In this work, we present the growth of single-crystalline BaTiO3 thin films on Si, exhibiting imprint-free switching, low coercivity, high remanent polarization, and no fatigue for over $10^{10}$ switching cycles. We accomplish this via the insertion of a SrSn1-xTixO3 layer on SrTiO3-buffered Si. This layer serves as a pseudo substrate that alleviates the thermal strain that the Si substrates imposes on the BaTiO3 layer, while simultaneously providing moderate compressive strain that stabilizes a pure out-of-plane polarization. Thus, our work paves the way toward the fabrication of Si-compatible, low-power-consuming ferroelectric devices for non-volatile
memory applications.
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Materials Science
Angular Emission Properties of Strained Transition-Metal Dichalcogenides
Lee Grimberg, Svyatoslav Kostyukovets and Moshe G. Harats
Monolayers of transition-metal dichalcogenides have shown that uniaxial strain changes both the photoluminescence emission energy and intensity. The changes are attributed to the band-structure
evolution under tensile strain where both the bandgap decreases and a direct-to-indirect transition occurs. This was shown for relatively high strains, whereas this is not the case at low strain values $<1\%$ in which in this work, we observe the erratic dependency of the photoluminescence intensity at low strain values as a function of strain. We find that the dominant physical property is the dependence of the optical-dipole emission on the
curvature of the substrate. We validate the behavior of the photoluminescence intensity with experimental angular emission spectroscopy (k-space imaging). These findings are supported by Finite-Difference Time-Domain simulations, in agreement with the experimental data. Our findings present the importance of choosing the right substrate for flexible devices based on transition-metal dichalcogenides.
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Soft Condensed Matter
Spatial patterning of force centers controls folding pathways of active elastic networks
Debjyoti Majumdar
We study the effect of the spatial distribution of active force dipoles on the folding pathways and mechanical stability of rigid-elastic networks using Langevin dynamics simulations. While it has been shown in Majumdar et al., J. Chem. Phys. 163, 114902 (2025) that a sharp collapse transition is evident in triangular (elastic) bead-spring networks under the action of contractile (or extensile) force dipoles distributed randomly across the network, here, we show that when the spatial distribution is correlated, e.g., like a patch in the center (“active core” model) or a band-like distribution along the periphery (“active periphery” model), the network undergoes only a partial decrease in size even at large forces, thereby showing an enhanced mechanical stability just from a spatial rearrangement of the active dipoles. Further, an active periphery network shows higher mechanical stability initially, for a range of forces, beyond which the active core network becomes more stable. Deformation in the network becomes irreversible beyond a threshold force, which depends on the type of distribution; for a uniform distribution of active dipoles, the irreversibility threshold almost coincides with the critical collapse point, it decreases for the active core system, and is decreased further for the active periphery system. It is shown that irreversibility arises due to plastic deformations in the form of crease formation which is not reversible even after the force is turned off or reversed. The folding pathways depend weakly on the temporal stochasticity of the active links, but are highly sensitive to any defects (missing bonds) in the network. Our findings, therefore, suggest active force localization (or delocalization) as a
prime method to dynamically alter the mechanical stability and reversibility of the underlying elastic network.
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Mesoscale and Nanoscale Physics · Cross-listed from physics.optics
Mapping the strong-to-weak coupling crossover in polymer-film microcavity lasers
Denis A. Sannikov, Nailya M. Urazova, Maksim D. Kolker et al. (+10 more)
Organic
semiconductors are particularly attractive for polaritonics due to their large
exciton binding energies and oscillator strengths. Among them, the ladder-type conjugated
polymer poly(paraphenylene) is distinguished by its rigid backbone, narrow
exciton linewidth, high photoluminescence
quantum yield, and enhanced photostability, making it an excellent candidate for organic polariton devices. While polariton lasing has been reported in various organic systems, systematic studies of the transition from polariton lasing to conventional
photon lasing within a single, well-controlled material platform remain limited. Here, we present planar organic microcavities incorporating MeLPPP as the active medium, in which continuous tuning of the effective cavity length within a single device enables us to map the strong-to-weak coupling transition across five distinct cavity-mode orders. We demonstrate an approximately eighteen-fold increase in the lasing threshold when crossing from polariton to
photon lasing. We further establish a quantitative framework in which the spectral dependence of the threshold governs a universal V-shaped blueshift of the emission energy across both coupling regimes. Finally, we show that vibron-mediated
exciton relaxation, previously identified in the strong-coupling limit, persists across the crossover: lasing-threshold minima track the vibron resonances throughout the coupling transition.
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All authors Denis A. Sannikov, Nailya M. Urazova, Maksim D. Kolker, Grigorij D. Ivanov, Anton D. Putintsev, Aleksandr V. Averchenko, Daria Khmelevskaia, Liliya T. Sahharova, Nikita S. Shlapakov, Ioannis Paschos, Pavlos G. Savvidis, Valentine P. Ananikov, Pavlos G. Lagoudakis
Soft Condensed Matter
Physical Models of Embryonic Epithelial Healing
Rafael Almada, Nuno Araújo and Pedro Patrício
Embryonic healing in epithelial tissues is distinct from adult wound healing, as it lacks inflammatory responses or immune
cell recruitments, making it ideal to test models of wound healing driven primarily by epithelial dynamics. Many models have been developed to describe this process, ranging from simple mechanistic models to more elaborate multiscale simulations. We review different classes of physical models, from discrete to continuum models, and how they address key questions about the mechanics, signaling, and coordination of
cells during wound closure. We highlight tensions between model complexity and interpretability and discuss recent efforts to bridge gaps across scales. Finally, we identify directions for hybrid modeling and model-experiment integration that could push forward our understanding of epithelial repair in development and disease.
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Mesoscale and Nanoscale Physics
Hybrid light-matter boundaries of graphene in a chiral cavity
Volker Karle, Oriana K. Diessel, Vasil Rokaj et al. (+1 more)
Recent advances in
chiral cavities that can couple coherently to two-dimensional materials have opened a powerful route to reshape electronic
topology without an external drive. Here we establish the bulk-boundary correspondence for
graphene embedded in a circularly polarized cavity. By combining exact diagonalization (ED) of zigzag ribbons, a semi-analytic T-
matrix for half-infinite
lattices, and analytical insights from a Dirac-Jaynes-Cummings model, we show that (i) every light-matter interaction-induced gap hosts pairs of unidirectional light-matter edge currents depending on the Chern number of the band while some of them are even bright; (ii) these
chiral states persist throughout the entire
photon ladder; and (iii) their dispersion, localization length and
photon distribution exhibit a universal scaling controlled by the light-matter interaction. Time-
evolution simulations further demonstrate that a dark electronic edge excitation can be converted into a bright and unidirectionally propagating current that remains coherent over long time scales. Our results predict an experimental signature of the hybrid band
topology and a blueprint for tunable
chiral channels in next generation
quantum optical solid-state devices.
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All authors Volker Karle, Oriana K. Diessel, Vasil Rokaj, Ceren B. Dağ
Superconductivity
Evolution of the superconductivity in pressurized La3-xSmxNi2O7
Qingyi Zhong, Junfeng Chen, Zhengyang Qiu et al. (+7 more)
Motivated by the discovery of superconductivity in
bilayer La$_3$Ni$_2$O$_7$ at 80 K and the increased superconducting transition temperature, $T_\text{c}$, up to 92 K in single
crystals of La$_2$SmNi$_2$O$_7$ under pressure, we systematically study the effect of Sm doping on the superconductivity and structure of La$_{3-x}$Sm$_x$Ni$_2$O$_7$ (0 $\leq$ x $\leq$ 1.5) under pressure. Experimental investigations in polycrystalline samples reveal that Sm doping monotonically decreases the
lattice constants $c$ and $a$, thereby enhancing
crystal structure distortion and leading to an
evolution of the metallic ground state in La$_3$Ni$_2$O$_7$ to an insulating state in La$_{1.5}$Sm$_{1.5}$Ni$_2$O$_7$. The maximum onset $T_\text{c}$ in compounds $x=0.9$ and 1.5 is 89 K, while the pressure that drives the emergence of superconductivity is higher for higher doping levels. The results suggest that the enhancement of $T_\text{c}$ in La$_{3-x}$Sm$_x$Ni$_2$O$_7$ is mainly affected by the compressed $c$
lattice before saturation, and the structure transition is critical for the emergence of superconductivity. Our experimental results provide insight into the influence of elemental substitution on nickelate
superconductors, offering a means to increase the transition temperature further.
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All authors Qingyi Zhong, Junfeng Chen, Zhengyang Qiu, Jingyuan Li, Xing Huang, Peiyue Ma, Mengwu Huo, Hongliang Dong, Hualei Sun, Meng Wang
Soft Condensed Matter
Wettability from Diffusion: A Universal Molecular Scaling Law
Lorenzo Agosta
Quantifying wettability at the nanoscale remains challenging, as macroscopic contact-angle measurements fail to capture the molecular interactions that define hydrophilic and hydrophobic behavior. We derive an analytical relation linking the water contact angle to the lateral
diffusion of interfacial molecules, establishing a quantitative connection between microscopic dynamics and macroscopic wettability. Molecular dynamics simulations confirm that the ratio of interfacial to bulk
diffusion uniquely determines the contact angle across the full hydrophilic-hydrophobic spectrum. This
diffusion-based formulation eliminates the need for droplet geometries or free-energy sampling, enabling quantitative assessment of wetting directly from short ab-initio molecular dynamics trajectories. The approach provides a universal and efficient route to evaluate surface affinity in reactive, defective, or confined environments.
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Mesoscale and Nanoscale Physics
Spin-Selective Second-Order Topological Insulators Enabling Cornertronics in 2D Altermagnets
Ning-Jing Yang, Zhigao Huang and Jian-Min Zhang
Recent progress in spintronics within the paradigm of altermagnets (AMs) opens new avenues for next-generation electronic device design. Here, we establish a
spin-corner locking mechanism that generates second-order topological states in two-dimensional (2D) altermagnetic systems, through effective model analysis. Remarkably, the breaking of Mxy
symmetry under uniaxial strain creates
spin-resolved corner modes, driving the system into a corner-polarized second-order topological
insulator (CPSOTI). Beyond critical strain, a topological phase transition to
quantum anomalous
Hall insulator occurs with quantized conductance. Through first-principles calculations, we identify two experimentally viable candidates for 2D intrinsic AM CrO and Cr$_2$Se$_2$O – which host robust CPSOTI. Moreover, we construct the topological phase diagram of CrO and predict the existence of an altermagnetic Weyl semimetal phase. Our findings open technological avenues in altermagnetism and higher-order
topology, while providing opportunities for coupling topological spintronics with cornertronics.
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Materials Science
Tuning the non-linear interactions of hybrid interlayer excitons in bilayer MoS2 via electric fields
Mathias Federolf, Alexander Steinhoff, Monika Emmerling et al. (+3 more)
Hybrid interlayer
excitons in
bilayer MoS2 are a promising platform for nonlinear optics due to their intrinsic dipolar character, which combines in-plane and out-ofplane dipole moments. In this work, we directly probe the nonlinear
exciton-
exciton interactions of hybrid interlayer
excitons. By applying an external out-of-plane electric field, we polarize the
excitons to enhance their mutual dipolar interactions, thereby deliberately favoring these repulsive contributions over competing attractive manybody corrections. We furthermore establish a fully microscopic theoretical description of these effects to explain the core experimental results. The tuning results in a significantly larger blueshift compared to the zero-field case and perspectively opens an avenue to even switch between repulsive and attractive interaction potentials. Our findings establish that strong nonlinearities can be tuned via an external electric field, providing a new degree of control over
exciton interactions beyond density tuning alone.
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All authors Mathias Federolf, Alexander Steinhoff, Monika Emmerling, Matthias Florian, Christian Schneider, Sven Höfling
Materials Science
Isothermal Annealing Effects on $\beta$-Relaxations and Crystallization Behaviors in Amorphous GeTe
Arune Makareviciute, Qun Yang, Tomoki Fujita et al. (+12 more)
A secondary $\beta$-relaxation process is often the dominant source of atomic dynamics below $T_\mathrm{g}$ in many glass forming systems. Recent studies reported the presence of $\beta$-relaxations in amorphous phase-change materials (PCMs) and showed that suppressing the $\beta$-relaxation via annealing in Ge$_{15}$Sb$_{85}$ can effectively slow down its crystallization kinetics. Yet, when Sb is replaced by Te, similar annealing protocol has little effect on the Te-rich
alloy Ge$_{15}$Te$_{85}$. Here, we investigate amorphous GeTe that is a Sb-free PCM, but with faster crystallization kinetics than Ge$_{15}$Te$_{85}$. Using powder mechanical dynamic spectroscopy, we observe a clear reduction of the excess-wing in the loss modulus upon isothermal annealing, indicating a suppression of its $\beta$-relaxation. Ultrafast calorimetric analysis and time-resolved optical reflectivity measurements show that, whereas as-deposited GeTe exhibit
stochastic crystallization behaviors, annealed samples crystallize more slowly with reduced stochasticity. Synchrotron X-ray scattering experiments reveal reinforced Peierls-like distortions in the amorphous structure after annealing, and demonstrate that, even if annealing introduces nucleation sites, it nonetheless slows down crystallization kinetics. These finding suggests that, in annealed GeTe, crystallization is limited by
crystal growth rate, which is retarded through the suppression of $\beta$-relaxation.
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All authors Arune Makareviciute, Qun Yang, Tomoki Fujita, Oliver Gross, Nico Neuber, Maximilian Frey, Jens Moesgaard, Cecile Chaxel, Julian Pries, Mads Ry Vogel Jørgensen, Frederik Holm Gjørup, Matthias Wuttig, Hai-bin Yu, Jiangjing Wang, Shuai Wei