Materials Science · Cross-listed from quant-ph
Isotopically enriched epitaxial CaWO$_{4}$ thin films for Er$^{3+}$ spin-photon quantum interfaces
Hanlin Tang, Kidae Shin, Ashwin K. Boddeti et al. (+10 more)
Rare earth ion (REI)-doped
oxide thin films are attractive for the application of
quantum interconnects due to their stable optical levels and scalability$^{1-3}$. Among them, Er$^{3+}$ doped CaWO$_{4}$ is promising because it possesses narrow optical linewidth transitions and a long
spin coherence time$^{4-6}$. The electron
spin coherence is limited at high temperatures by paramagnetic
impurities and by the presence of the 14.3% $^{183}$W
nuclear spin. To further increase the
spin coherence time at millikelvin temperatures, where the paramagnetic
impurities are frozen out, our approach is to synthesize chemically and isotopically purified thin films as a host material. We first grow non-isotopically enriched Er$^{3+}$ doped CaWO$_{4}$ thin films, which exhibit a 214(13) MHz photoluminescence (PL) inhomogeneous linewidth, indicating the thin film has high crystalline quality. We then grow isotopically enriched CaWO$_{4}$ thin films using an isotopically purified $^{186}$WO$_{3}$ source. Time of flight secondary ion mass spectrometry (ToF-SIMS) was used to measure the relative concentration of W isotopes. $^{183}$W, the only W isotope that has a net
nuclear spin and is the major cause of
spin decoherence, was at a relative abundance of 1.2%, a factor of 10 lower than natural abundance. We also observed PL emission from single ions after integrating nano-photonic devices with the thin film. These results establish isotopically engineered CaWO$_{4}$ thin films as a promising platform for future studies of
nuclear-
spin-limited coherence and for scalable rare-earth-ion-based
quantum nanophotonic devices.
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All authors Hanlin Tang, Kidae Shin, Ashwin K. Boddeti, Sebastian P. Horvath, Adam Turflinger, Joseph Alexander, Jeffrey A. Dhas, Zihua Zhu, Shuhang Pan, Jeff D. Thompson, Yingge Du, Frederick J. Walker, Charles H. Ahn
Mesoscale and Nanoscale Physics · Cross-listed from quant-ph
Gauge-covariant projected entangled paired states for interacting systems in a magnetic field
Wei Tang, Gunnar Möller, Frank Verstraete et al. (+1 more)
The
Hamiltonian for a system of itinerant particles on a two-dimensional
lattice in a uniform
magnetic field reduces the translational
symmetry to a
magnetic translation group, because of the need to choose a particular gauge for the vector potential. Nonetheless, in many situations all physical observables of the ground state remain entirely translation invariant. In this work, we introduce a projected entangled-pair state (PEPS) wavefunction with a pattern of virtual flux tensors, for which all physical expectation values are translation invariant by construction, possibly within an enlarged unit
cell reflecting any
symmetry breaking in the target state. Moreover, we show that the usual contraction and optimization methods for translation-invariant PEPS can be used, with the
magnetic flux per plaquette only entering as a continuous parameter in the tensor network contractions. Therefore, our approach provides a method for simulating an interacting many-body system in a uniform
magnetic field independently of the gauge choice for the vector potential and bypassing the need to consider extended
magnetic unit
cells.
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All authors Wei Tang, Gunnar Möller, Frank Verstraete, Laurens Vanderstraeten
Mesoscale and Nanoscale Physics · Cross-listed from cs.ET
Remotely programming the weights of a spintronic neural network by a radiofrequency broadcast signal
M. Menshawy, D. Sanz-Hernández, L. Mazza et al. (+7 more)
Selectively programming a large number of non-volatile synaptic weights without compromising scalability is a key challenge for in-
memory computing. Here, we experimentally demonstrate remote programming of synaptic weights in series-connected chains of 11
vortex-based
magnetic tunnel junctions using broadcast radiofrequency signals applied through a shared strip line. Because each junction is engineered with a distinct resonance frequency, programming relies on frequency-selective reversal of the
vortex-core polarity and therefore does not require individual access lines or selector devices. Reconfiguring the binary states of these chains strongly reshapes the continuous spectral transfer functions that determine the weighted sums performed on frequency-multiplexed RF inputs. This allows compact networks built from such chains to process high-dimensional RF-encoded inputs. We experimentally perform handwritten-digit classification and drone RF-signature identification using a two-chain network comprising only 22 synapses in total. After remote reconfiguration for each task, the spintronic network respectively reaches 93.9 +/- 2.3 % and 99.5 +/- 1 % test accuracy, on par with the software baseline. Broadcast RF programming thus provides a compact and scalable route to rapidly reconfigurable spintronic neuromorphic hardware.
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All authors M. Menshawy, D. Sanz-Hernández, L. Mazza, V. Puliafito, G. Finocchio, A. Jenkins, R. Ferreira, L. Benetti, J. Grollier, F.A. Mizrahi
Quantum Gases
Entropy Signatures of Collective Modes and Vortex Dynamics in Rotating Two–Dimensional Bose–Einstein Condensates
L. A. Machado, N. D. Chavda, B. Chatterjee et al. (+4 more)
We investigate the nonequilibrium dynamics of a two-dimensional rotating Bose gas confined in a symmetric anharmonic trap, employing the multiconfigurational time-dependent Hartree method for
bosons (MCTDHB). We study states ranging from
vortex-free configurations to multicharged (
giant)
vortices, prepared by tuning the rotation frequency, and analyze their response to sudden interaction and trap quenches. In
vortex-free states, interaction quenches induce regular breathing–like dynamics, whereas in the presence of
giant vortices they lead to
symmetry-breaking surface excitations. In contrast, trap deformations that excite quadrupole-like modes produce stable oscillations in
vortex-free condensates but trigger rapid, irregular, and effectively chaotic splitting dynamics in multicharged
vortices. To characterize these processes beyond conventional density and phase observables, we employ information-theoretic measures, including marginal and joint
entropies, mutual information, and Kullback-Leibler (KL) divergence, supplemented by an angular-resolved KL measure that captures
symmetry breaking and azimuthal localization. We find that chaotic splitting is accompanied by a pronounced growth of information-theoretic indicators, signaling the buildup of many-body correlations and increasing complexity in the system dynamics. Our results demonstrate the extreme sensitivity of
giant vortices to excitation protocols and establish information-theoretic measures as a powerful framework to quantify correlations and complexity in rotating
quantum gases.
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All authors L. A. Machado, N. D. Chavda, B. Chatterjee, M. A. Caracanhas, B. Chakrabarti, A. Gammal, R. P. Sagar
Statistical Mechanics
Energetics of stochastic limit-cycle oscillators: when does coupling reduce dissipation?
Anton F. Burnet, Vansh Kharbanda, David Tobias et al. (+1 more)
Non-linear oscillators serve important functions in many biological systems, including within the inner ear and neuronal networks. The sustainment of oscillations in noisy environments requires continuous energy dissipation, quantified by the steady-state
entropy production rate (EPR). We study an idealized, analytically tractable model of a
stochastic circular limit cycle and examine how mutual coupling in pairs and populations alters dissipation. For a single oscillator, the EPR depends on three key factors: intrinsic frequency, tangential velocity fluctuations, and mean tangential velocity. The dynamics are characterized by a dimensionless effective temperature given by the ratio of intrinsic relaxation and
diffusion timescales. For radial (amplitude), phase (Kuramoto-like), and Cartesian couplings, we derive analytical expressions for the EPR and confirm them numerically. Varying the effective temperature and system size strongly influences how the EPR depends on coupling strength and, in some cases, results in qualitatively distinct behaviors. Moreover, the coupling types affect the tangential velocity distributions differently. Notably, in all cases studied, Cartesian coupling reduces the EPR relative to the uncoupled system, irrespective of effective temperature and system size. The analysis of idealized non-linear oscillators reveals that different classes of coupling interactions and competing timescales present in the oscillators have distinct effects on energy dissipation.
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All authors Anton F. Burnet, Vansh Kharbanda, David Tobias, Benedikt Sabass
Quantum Gases
Deterministic Nucleation and Dynamics of Infilled Multiply-Charged Vortices in an Immiscible $^{87}\mathrm{Rb}$-$^{41}\mathrm{K}$ Mixture
R. Doran and K. E. Wilson
We propose a method for controllably generating multiply-charged
vortices in immiscible Bose-Einstein condensates. We achieve this by applying a
laser stirring technique to a $^{87}\mathrm{Rb}$-$^{41}\mathrm{K}$ mixture, where the
vortices generated are infilled by the secondary component. We numerically demonstrate that the charge of the
vortex can be tuned reproducibly by varying the stirring parameters, allowing the deterministic generation of stable infilled
vortices with high topological charge. We then consider the dynamics of these multiply-charged
vortices in a circular trap; in contrast to single-component condensates, we observe long-lived precession of the multiply-charged
vortices with a charge dependent frequency and collective breathing modes of the infilling component. For specific large winding numbers, we observe distinct dynamical instabilities leading to
vortex dislocation.
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Statistical Mechanics
Thermodynamic Parametrisation of the Vertebrate Lifetime Cycle Invariant: Biological Proper Time, Allometric Mass-Cancellation, and Clade-Specific Predictions
Mesfin Taye
Warm-blooded vertebrates accumulate approximately $\Nstar \approx 10^9$ cardiac cycles over a natural lifetime, a striking empirical regularity first quantified by Lindstedt and Calder yet lacking a physical interpretation. We propose that this invariance is consistent with a conserved thermodynamic budget, formulated here as the Principle of Biological Time Equivalence (PBTE). The framework rests on a constitutive closure $\dot{\Sigma} = \sigma_0 f$, which links the
entropy production rate to the intrinsic physiological frequency; integration over the lifespan yields $\Sigma_{\mathrm{life}} = \sigma_0 \Nstar$, so that the observed constancy of $\Nstar$ corresponds to an approximately constant lifetime
entropy budget. Algebraic exponent cancellation under Kleiber and Calder scaling laws, $\sigstar \propto M^{3/4+1/4-1}=M^0$, is consistent with mass-independence and reproduces the numerical value $N_0 \approx 1.52\times10^9$ without free parameters. The framework offers a thermodynamically consistent account of two outstanding problems: the origin of the numerical value of $\Nstar$ and the systematic deviations observed across clades. A multiplicative correction factor $\Phi_C$, constructed from physiological determinants – activity allocation, body temperature, mitochondrial efficiency, and extrinsic hazard – predicts long-lived clades as regimes of reduced effective
entropy production per cardiac cycle.
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Mesoscale and Nanoscale Physics
Structural Colours with Transition Metal Dichalcogenide Nanostructures
Ida Juliane Bundgaard, Catarina G. Ferreira, Yonas Lebsir et al. (+1 more)
We introduce transition metal-dichalcogenide (TMD) nanostructures as a promising platform for the realisation of structural colours. Processing of semianalytically calculated reflectance spectra of TMD nanosphere arrays shows a wide range of colours, which are obtained simply through tailoring the radius and separation of spheres in the array, with the size-dependent Mie modes of the nanoparticles being the primary contributor to the spectra. Additionally, it is demonstrated that further coverage of the colour space can be obtained by employing different materials or different
lattice unit
cells. Theoretical examination of the impact of the excitonic attributes of TMDs on the resulting structural colours indicates that self-hybridisation between nanoparticle modes and excitonic transitions may be employed for further tuneability. Moreover, the impact of TMD anisotropy on the structural colours is shown to be negligible for small structures at typical viewing angles, while the viewing angle itself may impact the colour. This work sets out to be a general investigation of TMD nanoarchitectures, with a focus on nanosphere arrays, for structural colours, by examining both inherent material features through the lens of colourimetry, and the ability of such structures to sustain a broad range of hues.
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All authors Ida Juliane Bundgaard, Catarina G. Ferreira, Yonas Lebsir, Christos Tserkezis
Statistical Mechanics · Cross-listed from quant-ph
Impact of thermal and dissipative effects in a periodically-kicked quantum battery
Sebastián V. Romero, Xi Chen and Yue Ban
Quantum batteries (QBs) have emerged as a promising route for fast energy storage and on-chip power supply in
quantum devices. Given the limited analytical understanding of open Floquet QBs, we employ the kicked-Ising model as a tractable platform to systematically study its performance under realistic conditions, including finite temperature effects and environmental dissipation. Starting from Gibbs states of the transverse-field Ising model, we incorporate thermal and decoherence effects along the
evolution, using both analytical and numerical approaches. Taking ergotropy as a central figure of merit, we characterize the injected and extractable energy, and identify regimes where charging remains robust despite environmental effects. Our results provide a systematic framework for assessing QB performance under thermal and dissipative effects.
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Statistical Mechanics
Beyond average: heterogeneous first-passage dynamics in many-particle systems with resetting
Juhee Lee, Seong-Gyu Yang and Ludvig Lizana
Stochastic resetting is well understood for single-particle first-passage processes, but its consequences for collective first-passage behavior remain less clear. We address this problem in a many-particle system where all particles reset to the position of the rightmost particle, a protocol motivated by problems in artificial selection and avoidance. We use
stochastic simulations of particles diffusing in a confining potential with an adsorbing boundary to examine two notions of group arrival: the first group-hitting time, when the first particle reaches the boundary, and the median group-hitting time, when half of them have reached it. We find that resetting produces broad hitting-time distributions with extended plateaus spanning several orders of magnitude. As the resetting rate increases, these plateaus extend and the mean group-hitting times grow rapidly. At the same time, the first-passage dynamics become increasingly heterogeneous. Consequently, the most probable and mean hitting times become widely separated, indicating the absence of a single characteristic time scale. These results demonstrate that the definition of group arrival is crucial for understanding and controlling collective first-passage behavior under resetting.
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Statistical Mechanics · Cross-listed from math.PR
"True" self-avoiding walks on general trees
Tuan-Minh Nguyen
We study the asymptotic behavior of “true" self-avoiding random walks on general infinite locally finite trees. In this model, the walk starts at the root and, at each step, from its current vertex chooses a neighboring edge to traverse with probability proportional to the current weight of that edge, where the weight of each edge after being traversed $n$ times is given by $w(n)=\exp(-\beta n)$. We show that the process exhibits a sharp phase transition between recurrence and transience. The critical value is determined by the branching-ruin number of the tree, which coincides with the Hausdorff dimension of the boundary of the tree under a suitable metric. We prove that the walk is almost surely transient when the branching-ruin number is greater than $1/2$, and recurrent when it is less than $1/2$. This resolves an open question posed by Kosygina.
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Soft Condensed Matter
A practicable method for the analysis of complex motion of biological and soft matter
Jun Ma
Biological function of living matter is fulfilled by complex motions of biological and soft matter. Unlike general motion is deterministic described by Newton's laws, these motions are mostly random and uncertain for the position in
stochastic process, being characterized as irregular trajectories of movement without a defined velocity. Like human fingerprint, the trajectory is the identity of the motion containing fundamental dynamical information. Such irregular trajectories randomly inter-wind and twist to each other to produce a complicated turmoil configuration in which so far the unrealized mechanism of motion is hidden. Nowadays, the analytical method for this fingerprint trajectory is still missed. Here we develop a practicable method to decipher complicated trajectory configuration, which uncovers abundant dynamical information hiding in irregular trajectories, revealing the remarkable
evolution of spatial-temporal micro-structure, thus leading to the novel systematic study of the dynamics of biological and soft matter.
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Materials Science
Mapping Reversal Pathways and Interaction Fields in Artificial Spin Ice
Brindaban Ojha, Matías P. Grassi and Vassilios Kapaklis
In artificial
spin ice (ASI),
magnetic interactions between nanomagnets determine both the stable states and the switching pathways under an applied field. Here, first-order reversal curve (FORC) measurements are used to map how these interactions govern magnetization reversal in square arrays as the element shape and spacing are varied. The FORC diagrams show that some geometries reverse more uniformly, whereas others exhibit broader, more asymmetric responses, indicating stronger interaction effects and more complex reversal pathways. Combined FORC analysis and micromagnetic simulations also capture subtle changes in internal magnetization textures during switching, linking local behavior within individual elements to collective behavior across the array. These results establish FORC as a practical tool for mapping and engineering interaction landscapes, with direct relevance to reconfigurable
magnetic reservoirs and neuromorphic functionality.
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Quantum Gases
Fragmentation Temperature of 1D and 3D Quantum Droplets in a BEC Mixture
Jeroen Van Loock, Denise Ahmed-Braun and Jacques Tempere
In a mixture of two Bose-Einstein condensates, the interactions can be tuned such that self-bound objects called
quantum droplets appear. Whereas the ground states of such
quantum droplets at finite temperature have been studied for three- and one-dimensional configurations, the possible fragmentation of these droplets has so far not been considered in these studies. In this paper, we show that droplets can lower their free energy by splitting or fragmenting in a combination of multiple smaller droplets and/or a gas. Three-dimensional droplets will split when the interspecies interaction strength is considerably stronger than the intraspecies interaction strength, and the number of atoms is of the same order as the minimum number of atoms necessary to form a droplet. One-dimensional droplets will fragment as long as the intraspecies and interspecies interactions strength do not vary too much in strength and the density is not to big compared with the scattering length. If the temperature rises, 1D droplets will split by expelling atoms, forming a gas of predominantly free atoms and pairs of atoms. These pairs remain present in the system up to considerably high temperatures compared to the transition temperature. Our results provide important insights on the stability of these droplets.
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Disordered Systems and Neural Networks · Cross-listed from quant-ph
New non-Euclidean neural quantum states from hyperbolic Lorentz recurrent architectures
H. L. Dao
In this work, we construct new non-Euclidean neural
quantum states (NQS) based on
hyperbolic Lorentz recurrent architectures (RNN/GRU). These constructions, together with the Poincare RNN NQS also newly constructed here, extend the class of previously introduced non-Eucllidean NQS which consists only of Poincare
hyperbolic GRU. Using the Heisenberg J1J2 and J1J2J3 models consisting of 100
spins in the Variational Monte Carlo (VMC) setting, we show that the four
hyperbolic RNN/GRU NQS variants are always able to furnish better representations of the ground state wavefunctions of the
quantum systems than their respective Euclidean counterparts with the same architecture. In our experiments, among the four
hyperbolic NQS, Lorentz RNN stands out in particular because despite having almost three times fewer parameters, it is capable of surpassing the more complex Poincare GRU and Lorentz GRU to emerge as the best overall
hyperbolic NQS ansatz on many instances involving different J2 and (J2,J3) couplings. Given the findings from this work showing that the four newly constructed
hyperbolic RNN/GRU NQS ansatze are able to outperform the well-established Euclidean RNN/GRU NQS in Heisenberg
spin models, we establish the utility and efficiency of the
hyperbolic Lorentz RNN/GRU NQS as well as the Poincare RNN/GRU NQS for future variational studies of
quantum many-body systems, especially those exhibiting a hierarchical structure in the form of the different degrees of nearest-neighbor interactions.
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Materials Science · Cross-listed from physics.app-ph
Complementary-polarity double-layer LiTaO3 resonators for symmetry-selective SH2 excitation with ultrahigh electromechanical coupling (kt^2 = 25.7%)
Hao Yan, Zhen-hui Qin, Zhi-Wen Wang et al. (+7 more)
We report a structurally simple double-layer lithium tantalate (LiTaO3) bulk acoustic resonator that enables
symmetry-selective excitation of the second-order thickness-shear (SH2) mode with ultrahigh electromechanical coupling. Two 31 deg Y-oriented single-
crystal LiTaO3 films are rotation-bonded with complementary polarization (+X/-X) and driven by a longitudinal electric field. Matching between the effective piezoelectric
symmetry and the SH2 mode yields an effective electromechanical coupling coefficient of kt^2 = 25.7% at 5.24 MHz. To our knowledge, this is the highest kt^2 reported for a LiTaO3 resonator architecture to date. The measured response is dominated by the target SH2 mode, with only weak parasitic features in the operating band. The structure is also tunable: the resonance frequency and coupling can be adjusted through
geometric parameters while maintaining stable modal behavior, indicating good process tolerance. Finite-element analysis further suggests straightforward frequency scaling beyond 5 GHz by reducing the film and electrode thickness while preserving approximately 25% kt^2. In addition, introducing a SiO2 compensation layer is predicted to improve the temperature coefficient of frequency to approximately -25 ppm/deg C. These results establish complementary-polarity double-layer LiTaO3 as a practical platform for high-coupling, spurious-suppressed acoustic resonators and provide a scalable route toward wideband ultrasonic resonators, filters, and related transducers.
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All authors Hao Yan, Zhen-hui Qin, Zhi-Wen Wang, Shu-Mao Wu, Chen-Bei Hao, Hua-Yang Chen, Sheng-Nan Liang, Ke Chen, Si-Yuan Yu, Yan-Feng Chen
Superconductivity
Cosine bands, flat bands and superconductivity in orthorhombic iron selenide
Ian D R Mackinnon and Jose A Alarco
Electronic band structures (EBSs) for orthorhombic beta FeSe1-x at less than 16 K and up to 23 GPa using experimentally determined
cell dimensions are evaluated for cosine-shaped bands near, or crossing, EF. Cosine shaped bands are present in reciprocal directions parallel to the c axis at all pressures. Calculations using a P1
cell derived from Cmma
symmetry with a 2c superlattice moderates the effect of intersecting bands to 9.0 GPa. This approach enables determination of a superconducting gap consistent with experimentally determined values. Key influences on charge distribution and transfer in the interplanar region of beta FeSe1-x are lone pair electrons which feature as flat bands (FBs) near EF along GZ in an EBS. FBs also influence the
topology of
Fermi surfaces as pressure increases and in directions parallel to the c* direction (i.e. offset along ky) within the Brillouin zone. At the
Fermi surface along b*, cosine bands split and align favorably for electron-hole pairing with nodal inflection points located at EF. For P greater than 12.0 GPa, FBs interact with folded cosine bands invoking additional band dispersions. These calculations suggest that FBs participate in, and with increased pressure, enhance and sustain the superconducting properties of beta FeSe1-x to 23 GPa.
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Materials Science
Atomistic Mechanisms of Temperature-Dependent Ion Track Formation in Gallium Nitride under Swift Heavy Ion Irradiation
Jiayu Liang, Shaowei He, Wenlong Liao et al. (+8 more)
The radiation tolerance of gallium nitride under extreme conditions is critical for its deployment in next-generation electronic and optoelectronic devices, yet the microscopic mechanisms governing swift heavy ion induced damage at elevated temperatures remain poorly understood. Therefore, this study employs a coupled approach including the two-temperature model and molecular dynamics simulations to resolve the entire processes of ion track generation induced by swift heavy ions irradiation across a wide temperature range. A temperature-driven morphological transition of ion tracks, evolving from discontinuous segments to continuous tracks composed of isolated nanobubbles, and ultimately to fully continuous channels is observed. Under lower electronic stopping loss of 430 MeV Kr irradiation, increasing temperature significantly enhances track visibility, enlarges track radii and promotes nanobubble formation. For higher electronic stopping conditions of 1171 MeV Ta irradiation, continuous ion tracks consisting of discontinuous nanobubbles (~1.5 nm radius) emerge already at 300 K, followed by a thermally activated transition into continuous channels with further radial expansion. At the atomic scale, SHI irradiation induces decomposition of wurtzite GaN into Ga clusters and N2 molecules along the ion trajectory, with Ga-rich regions and recrystallized wurtzite phases accumulating near bubble interfaces, while N2 preferentially segregates within bubble cores. Additionally, zincblende nanodomains nucleate around ion tracks and exhibit strong spatial correlation with radiation-induced dislocation networks, particularly screw dislocations, providing potential pathways for leakage current and increased susceptibility to single-event burnout.
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All authors Jiayu Liang, Shaowei He, Wenlong Liao, Tan Shi, Hang Zang, Yonghong Li, Xiaojun Fu, Chuanjian Yao, Chaohui He, Jianan Wei, Huan He
Mesoscale and Nanoscale Physics
Non-Bloch band theory of nonlinear eigenvalue problems
Kota Otsuka and Kazuki Yokomizo
Nonlinear
eigenvalue problems arise in a wide range of physical systems, in which system parameters depend on the
eigenvalue. Such systems have been proposed to exhibit an extreme sensitivity of their spectra to boundary conditions, which leads to the breakdown of conventional topological characterizations. In this work, we establish a non-Bloch framework for calculating continuum bands that reproduce the spectra of the nonlinear system with open boundary conditions. This non-Bloch band theory enables us not only to calculate the
eigenvalues but also to reveal phenomena unique to the nonlinear system. We further investigate the topological bulk-boundary correspondence in a nonlinear Chern
insulator within an extended version of this framework.
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Strongly Correlated Electrons
Umklapp correction to Landau damping and conditions for non-trivial modifications to quantum critical transport
Vibhu Mishra
We compute the particle–hole bubble for an Ising-nematic metal when the critical
Fermi surface approaches the Brillouin zone boundary for $d=2$ dimensions. We find two qualitatively distinct contributions: i)~the standard antipodal piece, which gives $\Pi_{\rm{ATP}}(\mathbf{q}, i\Omega)\propto\Omega/q$ and ii)~an additional umklapp piece from electrons near the zone boundary, which gives $\Pi_{\rm{U}}(\mathbf{q}, i\Omega)\propto \Omega^\alpha$ at the minimum umklapp momentum $q\approx \Delta_q$ with $\alpha = 2/3 $ or $1/2$ depending on the temperature $T$. At high $T$ when $\alpha = 1/2$, the minimum $T$ for the activation of linear/quasi-linear in $T$ resistivity, which is expected to be $T_U \propto \Delta_q^3$ from $z=3$ criticality, could potentially get reduced to $T_U \propto \Delta_q^4$ due to the $\sqrt{\Omega}$ term and discuss why we find only one hyper-specific scenario where this possibility might be realized. For $d=3$ the umklapp contribution gives $\Pi_{\rm{U}}\sim \Omega$ irrespective of $T$ therefore $T_U$ is not modified in this case.
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Materials Science
Nitrogen doping induced metal-insulator transition with iso-symmetric character in rutile VO2
Baichen Lin, Shanquan Chen, Yubo Zhang et al. (+18 more)
Metal-
insulator transitions (MITs) in correlated
oxides offer immense potential for next-generation Mottronic devices. However, their integration into practical applications is often hindered by the coupling of MITs with
symmetry-lowering structural phase transitions, which limits switching speed and endurance. In this study, we engineered an iso-symmetric MIT on average in epitaxial rutile VO2 thin films via an in-situ nitrogen doping strategy. Nitrogen incorporation effectively suppresses V-V dimerization, enabling an iso-symmetric MIT, while preserving the original
crystal symmetry. Furthermore, in-operando time-resolved optical reflectivity measurements revealed a shortened switching time in nitrogen-doped films, highlighting their enhanced performance. Our findings provide critical insights into the underlying mechanisms of MITs and introduce anion doping as a powerful tool for tailoring phase transitions in strongly correlated electron systems. This approach opens new avenues for the development of high-performance electronic and photonic devices.
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All authors Baichen Lin, Shanquan Chen, Yubo Zhang, Yangyang Si, Haoliang Huang, Chuanrui Huo, Frans Munnik, Yongqi Dong, Lu You, Jian Shao, Yu-Chieh Ku, Nguyen Nhat Quyen, Aryan Keshri, Zhenlin Luo, Weiwei Zhao, Chun-Fu Chang, Chih-Wei Luo, Sujit Das, Shiqing Deng, Chang-Yang Kuo, Zuhuang Chen
Soft Condensed Matter
Density-protected states in active matter under virtual confinement
Giuseppe Fava, Francesco Ginelli and Benoît Mahault
We investigate photo-responsive structure formation in a minimal model of dry active nematics. Combining microscopic simulations with the analysis of the corresponding hydrodynamic theory, we show that the system generically self-assembles into a dense, nematically ordered ring at the boundary of compact illumination patterns. Remarkably, this boundary structure gives rise to a disordered core whose density is self-selected and independent of the global particle density. Our analysis reveals that these protected states emerge from a generic interplay between local nematic
alignment and
curvature-driven active currents. These results identify a robust route to boundary-induced structure formation in active matter and provide experimentally testable predictions.
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Disordered Systems and Neural Networks
Electrical conductivity of crack-template-based transparent conducting films: mean-field approximation, effective-medium theory, and simulation
Yuri Yu. Tarasevich, Andrei V. Esrkepov and Irina V. Vodolazskaya
In this work, crack-template-based transparent conducting films were modeled as networks corresponding to the edges of a two-dimensional Poisson–Voronoi diagram. Two types of networks were considered: the original one, in which the conductance of each edge was inversely proportional to its length, and the effective one, in which all edges had the same conductance obtained from the effective-medium theory. The mean-field approximation was used for analytical evaluation of the electrical conductivity. Direct numerical calculations for the Poisson–Voronoi diagram showed that the mean-field approximation overestimated the effective conductivity of the original network by approximately 13%, and of the effective network by 79%. In addition, a honeycomb network with an edge conductance distribution corresponding to the Poisson–Voronoi diagram was studied: for it, the predictions of the effective-medium theory turned out to be more accurate than for the Poisson–Voronoi diagram, which was explained by the greater structural homogeneity of the periodic honeycomb
lattice. The results indicate that, when modeling crack-template-based transparent conducting films, the application of the mean-field approximation may lead to significant errors if the resistance of individual conductors is not simply proportional to their length. This possibility is discussed as a motivation for future studies of hierarchical cracks with variable width, which are not directly investigated here.
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Materials Science
Phase transformation kinetics in MoS2 governed by S-S repulsive interactions and defect-interface compatibility
Pai Li, Ziao Tian, ZengFeng Di et al. (+1 more)
The metastable T' phase in monolayer MoS2 exhibits remarkable persistence despite a strong thermodynamic driving force toward the stable H phase. Using machine learning-accelerated molecular dynamics and first-principles calculations, we reveal that this kinetic arrest originates from repulsive S-S interactions, which impose high energy barriers during both nucleation and grain boundary propagation. While sulfur vacancies can alleviate these barriers in certain interfaces, they fail to accelerate transformation at the most stable interface, ZZ-Mo|-, due to their thermodynamic instability there. Instead, vacancies migrate into the T' phase, leaving the advancing front defect-free. Direct simulations of nanostructures confirm that H-phase nucleation initiates at corners or edges, and all observed growth fronts adopt the ZZ-Mo|- configuration, consistent with its low interfacial energy but slow kinetics. Our work establishes that phase transformation in 2D materials is governed not by global defect concentration, but by the local compatibility between defects and moving interfaces, offering a new paradigm for controlling structural transitions through interface-specific design.
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All authors Pai Li, Ziao Tian, ZengFeng Di, Feng Ding
Strongly Correlated Electrons
Dichroic Raman probes for chiral edge modes
Avedis Neehus and Johannes Knolle
The identification and manipulation of charge-neutral fractionalized quasi-particles, in particular
chiral edge modes (CEM), is a long-standing quest in physics. Remarkably, the microscopically mediated interaction between light and charge-neutral excitations in Mott-Hubbard
insulators can take an identical form to the Raman coupling between light and particles with electric charge. However, since CEMs are Raman-inactive due to conservation of
lattice momentum, Raman probes have been deemed unsuitable for their identification. Here, using the Kitaev
quantum spin liquid (KSL) as an illustrative example, we demonstrate that the long-range correlated disorder inherent to a closed edge can lead to a Raman circular dichroism (RCD) signal that avoids suppression by linear and angular momentum selection rules, and exhibits a dependence on experimentally tunable length and energy scales that are characteristic of CEM. Having calculated the low-frequency RCD response of generic KSL, we argue that the interaction of the
chiral matter
fermion with the $\Ztwo$ boundary charge leaves a unique fingerprint of the KSL via the anisotropic Zeeman field dependence.
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Materials Science · Cross-listed from physics.app-ph
Evidence of Micron-Scale Ion Damage in (010), (110), and (011) ${\beta}-Ga_2O_3$ Epitaxial Layers
Carl Peterson, Chinmoy Nath Saha, Yizheng Liu et al. (+2 more)
We report on the experimental observation of up to 11.5 ${\mu}m$ deep charge depletion in (010), (110), and (011) ${\beta}-Ga_2O_3$ epitaxial layers due to ion damage from sputtering and inductively coupled
plasma (ICP) etching processes whereas charge depletion in (001) ${\beta}-Ga_2O_3$ epitaxial layers was minimal. The orientation-dependent reduction in CV-measured charge density was first observed in $NiO_x$ reactively sputtered heterojunction p-n diodes (HJDs). When compared to reference low-damage Schottky barrier diodes (SBDs), the sputtered HJDs showed a $9.4{\times}$ increase in the specific on resistance $(R_{on,sp})$ and 85% reduction in net donor concentration $(N_D - N_A)$ at zero bias for sputter-damaged HJDs on (010) epitaxial layers whereas HJDs on (001) remained unchanged. Similarly, sputtered SiO2 caused a reduction of $N_D - N_A$ 11.5 ${\mu}m$ deep into the (010) material. Next, SBDs were fabricated on ${\beta}-Ga_2O_3$ surfaces previously etched via a BCl3 based ICP process and compared to SBDs on un-etched surfaces. The (010) SBDs on etched surfaces exhibited a $7.7{\times}$ increase in $R_{on,sp}$ and a 91% reduction in $N_D - N_A$ at zero bias where the (001) etched diodes exhibited little change. Additionally, (110) and (011) diodes fabricated on ICP damaged surfaces also saw a ~82% reduction in $N_D - N_A$ at zero bias, indicating (110) and (011) are also susceptible to ion damage. Damage in the (010), (110), and (011) diodes is potentially caused by energetic ions that travel into the open channels present along the [010] direction and create compensating point defects which could potentially diffuse further.
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All authors Carl Peterson, Chinmoy Nath Saha, Yizheng Liu, James S. Speck, Sriram Krishnamoorthy
Disordered Systems and Neural Networks
Solution of a chaotic neural network at fixed connectivity
Albert J. Wakhloo
We calculate the moments and response functions of a nonlinear random recurrent neural network in the large-$N$ limit using a diagrammatic technique. Our approach does not require averaging over synaptic weights and gives the first nontrivial term in a $1/\sqrt{N}$ expansion of general intensive-order correlation functions, proving a recent
conjecture by Shen and Hu as a special case. Our results provide an analytical link between synaptic connectivity, correlations in spontaneous activity, and the response of a network to small perturbations.
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Materials Science
Electron-phonon coupling across the TMD/hBN van der Waals interface
G. Gatti, C. Berthod, J. Issing et al. (+18 more)
Many-body interactions can couple electronic states in one layer with collective excitations in the adjacent layer, providing a route to tailor properties of
heterostructures. However, detecting and quantifying interlayer many-body interactions proved a major challenge. Here, we demonstrate that quasiparticles in monolayer transition metal dichalcogenides (TMDs) are dressed by a remote cloud of
phonons in the adjacent hexagonal boron nitride slab. Using angle resolved photoemission, we identify replica bands in the TMDs which are a clear fingerprint of long-range electron-
phonon interaction. We develop a modified Fröhlich model that shows semi-quantitative agreement with the experimental spectral functions. Our analysis shows that remote electron-
phonon coupling is a generic property of interfaces with hBN. This has implications for electron mobilities in 2D materials, for superconductivity and possibly for moiré correlated phases.
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All authors G. Gatti, C. Berthod, J. Issing, M. Straub, S. Mandloi, Y. Alexanian, J. Avila, P. Dudin, T. K. Kim, M. D. Watson, C. Cacho, K. Watanabe, T. Taniguchi, W. Wang, N. Clark, R. Gorbachev, N. Ubrig, I. Gutierrez-Lezama, A. F. Morpurgo, A. Tamai, F. Baumberger
Soft Condensed Matter · Cross-listed from physics.flu-dyn
Synchronized molecular dynamics method for thin-layer flows of complex fluids
Shugo Yasuda, Kotaro Oda, Fumito Muragaki et al. (+3 more)
We propose a multiscale computational method for thin-layer flows of complex fluids, termed the synchronized molecular dynamics (SMD) method, which directly couples local molecular dynamics (MD) simulations with a macroscopic lubrication description. In thin layers, the flow can be decomposed into cross-sectional dynamics that are strongly influenced by interfacial effects, and streamwise transport along the channel. The SMD method exploits this separation of scales by sparsely distributing local MD
cells along the channel and synchronizing them through macroscopic conservation laws. In this framework, the macroscopic continuity equation is enforced by iteratively updating the external forces applied to each MD
cell, thereby allowing the cross-sectional velocity profiles and the streamwise pressure distribution to be obtained without prescribing constitutive relations or boundary conditions. The method is validated for pressure-driven and wall-driven flows of Lennard–Jones fluids in a wedge-shaped channel, demonstrating excellent agreement with a modified Reynolds equation that accounts for boundary slip. The SMD method is further applied to polymeric lubrication flows modeled by the Kremer–Grest chain model. At large pressure differences, the present approach naturally captures pronounced shear-thinning behavior coupled with microscopic
polymer conformation dynamics. The results demonstrate that the SMD method provides an efficient and physically consistent framework for the multiscale simulation of complex fluid thin-layer flows.
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All authors Shugo Yasuda, Kotaro Oda, Fumito Muragaki, Yuta Taketa, Masashi Iwayama, Tomohide Ina
Mesoscale and Nanoscale Physics
Geometry selective colossal negative dielectric permittivity in CaFe2O4 nanostructures
Sourav Sarkar and Kalyan Mandal
Negative permittivity metamaterial is a scientifically rich avenue due to its tremendous application in several arena of materials research including novel superlens, band-gap materials, invisibility cloaks,
antenna and filter design. Traditionally, epsilon negative (ENG) behaviour is achieved in multi-phase composites with the addition of conducting metal fillers. However, this study reports colossal ENG feature in a single phase Calcium Ferrite for a particular nano hollow spherical (NHS) morphology, without the use of any filler. On the contrary, the same material synthesized in a different morphology, namely, nano solid sphere (NSS) shows conventional dielectric behaviour. Occurrence of ENG is successfully interpreted with the phase inversion of dominant polarization within the hollow cavity of NHS. This report marks a significant step in realizing colossal ENG in a single phase material just by restructuring the nanoscale morphology.
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