Materials Science · Cross-listed from physics.app-ph
Imaging atomic scale stochasticity: noise in the nearly commensurate charge density wave of 1T-TaS$_2$ for leaky-integrator-and-fire neuromorphic emulator
Michael Verhage
Low-dimensional materials are promising materials for emulating
neuron-like firing were understanding of the atomic-scale origin of this behavior can benefit integration into neurormophic hardware. Using scanning tunneling microscopy (STM) as a highly local probe of correlations in the charge density wave (CDW), we study atomic-scale CDW noise in $1T\text{-}\mathrm{TaS}_2$ at room temperature. We statistically analyze the tunnel-junction noise and, to explain the temporally correlated current bursts, introduce a mesoscopic model in which the fractal structure and reorganization of CDW discommensurations are related. This noise mimics leaky-integrate-and-fire
neuron dynamics. Our results show that atomic-scale current bursts in the tunnel junction can act as effective nonlinear elements in spiking neural emulators, enabling bioinspired processing through rich CDW dynamics at room temperature and supporting the miniaturization of spiking devices.
Read the full abstract ▾
Soft Condensed Matter
Jerky Motion of Active Granular Particles
Alexander P. Antonov, Marco Musacchio, Hartmut Löwen et al. (+1 more)
Abrupt transitions between rest and motion can render the standard Newtonian description – based on position, velocity, and acceleration – incomplete, requiring higher-order derivatives such as the jerk, the third time derivative of position. Here, we show that the interplay between activity and dry friction gives rise to robust jerk-dominated dynamics in self-propelled particles: the particle speed increases quadratically with time under an active force, in contrast to the linear growth expected for conventional Newtonian dynamics. We demonstrate this behavior analytically, numerically, and experimentally using active vibrobots self-propelling on a vertically vibrating plate at low vibration amplitudes, where surface asperities generate dry friction and, thus, give rise to jerky motion when combined with activity. Our results establish dry friction as a simple mechanism for realizing higher-order dynamics in active matter and suggest that jerky dynamics may arise broadly in nonequilibrium systems with frictional contacts.
Read the full abstract ▾
All authors Alexander P. Antonov, Marco Musacchio, Hartmut Löwen, Lorenzo Caprini
Mesoscale and Nanoscale Physics
Visualizing flat-band spatial renormalization in rhombohedral graphene superlattices
Peng-Cheng Pan, Shihao Zhang, Yang Zhang et al. (+10 more)
Rhombohedral
graphene/hBN moiré superlattices exhibit flat-band-driven emergent phases, including superconductivity and the fractional
quantum anomalous Hall effect (FQAHE), yet the microscopic role of the moiré potential remains unclear. Here, using scanning tunneling microscopy, we visualize moiré-modulated spatial renormalization of flat bands in rhombohedral pentalayer and tetralayer
graphene/hBN superlattices. We observe spatially hierarchical filling, manifested as periodic energy shifts of the flat bands at the moiré scale, leading to spatial reshaping of correlated states in the interacting regime. Remarkably, this modulation vanishes below a ~10 nm moiré period–the same threshold below which the FQAHE is absent. Theoretical modeling attributes this mechanism to atomic-corrugation-induced charge redistribution. Our work provides real-space visualization of moiré-engineered flat-band reconstruction, resolving a key link between moiré periodic potential and emergent topological order.
Read the full abstract ▾
All authors Peng-Cheng Pan, Shihao Zhang, Yang Zhang, Ji Huang, Ling-Hui Tong, Chen-Chen Xu, Yuan Tian, Li Zhang, Lijie Zhang, Yuanyuan Hu, Wen-Xiao Wang, Zhihui Qin, Long-Jing Yin
Materials Science
Thermal diffuse scattering in TEM: complex absorptive potentials compared to the frozen phonon model
Martin Hájek and Ján Rusz
In transmission electron microscopy, electrons undergo inelastic scattering primarily through
phonon excitations, known as thermal diffuse scattering. To capture the inelastic scattering effects on the elastic scattering components, absorptive effects must be included in the modeling of electron propagation, accounting for the gradual depletion of the elastic channel of the electron beam. Several approaches to modeling this absorption exist. In this paper, we compare the widely used complex absorptive potentials method to the more elaborate frozen
phonon model, based on correlated atomic motion and on the Einstein model of atomic motion.
Read the full abstract ▾
Mesoscale and Nanoscale Physics
Exciton fine structure in nanocrystals: effect of cuboidal and spheroidal shapes
M. A. Semina, O. O. Druzhinina, A. A. Golovatentko et al. (+1 more)
We present the theory of the band-edge
exciton fine structure in nanocrystals (NCs) with spheroidal and cuboidal shapes. The effects of the cubic
symmetry of the
crystal lattice, the cubic shape of the NC, and NC uniaxial anisotropy on the hole energy states and electron-hole exchange interactions are considered non-perturbatively.
Symmetry analysis yields an effective
Hamiltonian for the
exciton fine structure, parameterized by one constant for hole energy splitting and five independent constants for exchange interaction. Numerical calculations reveal that in uniaxially anisotropic zinc-blende NCs, the sign of the hole ground state splitting depends on the material parameters and on the orientation of the anisotropy axis relative to the crystallographic axes. Beyond the conventional bulk cubically-symmetric contribution to the exchange interaction, which originates from Bloch-function
symmetry and is typically negligible, in nanocrystals, we identify the contribution arising from the cubic
symmetry of the envelope wavefunction. This cubically symmetric envelope-induced short-range exchange is non-negligible in cuboidal NCs and induces a pronounced splitting of the dark
exciton states. We further analyze the influence of uniaxial anisotropy of the exchange constants on both the
exciton fine structure and the oscillator strength. Special
attention is paid to NCs, where the anisotropy of the exchange constants is comparable to a relatively small hole energy anisotropic splitting.
Read the full abstract ▾
All authors M. A. Semina, O. O. Druzhinina, A. A. Golovatentko, A. V. Rodina
Mesoscale and Nanoscale Physics
Long-Range Order and Composite Boson Condensation in Lattice Quantum Hall States
Fabian J. Pauw, Nathan Goldman and Felix A. Palm
Topological states of matter, such as
quantum Hall states, are characterized by the absence of local order parameters. In the continuum, their topological order has been reinterpreted as the condensation of nonlocal composite
bosons, but this condensation and the resulting long-range correlations have so far eluded direct confirmation beyond the simplest trial states. Here, we apply tensor-network methods to
lattice Hamiltonians hosting
quantum Hall states, revealing this exotic order directly in interacting ground states and demonstrating both the long-range correlations and the condensation of composite
bosons. These correlations define a nonlocal order parameter that identifies phase transitions between trivial and topological phases, for both bosonic and fermionic models. The corresponding operators are accessible through site-resolved, local measurements on an extensive number of particles, making them directly probable in
quantum simulators. Our work opens new avenues for microscopic studies of topological
quantum matter beyond the reach of traditional solid-state approaches.
Read the full abstract ▾
Statistical Mechanics
Ideal Bose-Einstein condensation in the canonical ensemble: exact asymptotic estimates from large deviations
Giacomo Gradenigo, Dario Lucente and Luca Salasnich
In this work we present a large-deviations approach to the calculation of the canonical partition function for free
bosons. Three-dimensional Bose-Einstein condensation is studied in the fixed-density ensemble as a function of the dimensionless density $\varrho = \rho \lambda_T^3$, with $\rho=N/L^3$ the standard particle density, $\lambda_T$ the thermal wavelength, $L$ the linear size of the box and $N$ the total number of particles. A large-deviations approach in terms of the dimensionless parameter $\ell=L/\lambda_T$ allows us to provide exact asymptotic estimates of the canonical partition function both above and below the critical density $\varrho_c$ for Bose-Einstein condensation. We show how this approach allows to explicitly account for finite-size effects and how it fully captures the first-order aspects of the transition, allowing us to explicitate its driving mechanism in terms of the competing probabilities of normal and condensed phases. The proposed large-deviations approach allows then to obtain in all regimes explicit and simple analytical expressions, at the leading order in the large parameter $\ell$, for both the average fraction of particles in the ground state, the condensate fraction $\langle n_0(\varrho) \rangle = \langle N_0(\varrho) \rangle/N$, and for its fluctuations, $\sigma_0(\varrho) = \sqrt{\langle N_0^2(\varrho)\rangle - \langle N_0(\varrho)\rangle^2}/N$, retrieving for instance the anomalous scaling $\sigma_0(\varrho)\sim 1/V^{1/3}$ in the condensed regime, $\varrho > \varrho_c$. Our large-deviations asymptotic estimate, by analytically clarifying the mixed-order nature of Bose-Einstein condensation, allows then to reveal the similarity between this transition and other mixed-order transitions, as for instance the localization transition in the Discrete Non-Linear Schrödinger Equation.
Read the full abstract ▾
Mesoscale and Nanoscale Physics
Engineering Plasmons in Oxide/Graphene Heterostructures via Interfacial Charge Transfer
Yuanchen Chi, Dongxu Di, Michael Fralaide et al. (+2 more)
Interfacial charge transfer provides an effective route for tailoring the optical and electronic properties of two-dimensional materials. Here, we investigate infrared surface plasmon polaritons in oxide/
graphene heterostructures using scattering-type scanning near-field optical microscopy. Ultrathin oxide overlayers deposited by physical vapor deposition enable systematic engineering of
graphene plasmons through interfacial charge redistribution. MoOx strongly enhances the plasmonic response, producing a longer plasmon wavelength, stronger fringe contrast, and reduced damping, whereas a subsequently deposited ZnOx overlayer partially reverses these changes. Energy-dependent nano-infrared imaging combined with quantitative modeling reveals an increased
graphene carrier density and the resulting modification of the plasmon dispersion. Thickness-dependent measurements show a rapid increase in charge-transfer doping at sub-nanometer MoOx thicknesses, followed by a weaker long-range contribution at larger overlayer thicknesses. Electrostatic gating further modulates the carrier density and produces a nonlinear response consistent with gate-dependent interfacial charge redistribution. In addition, an approximately 3-nm-thick MoOx overlayer stabilizes the plasmonic response for at least seven months under ambient conditions. These results establish oxide/
graphene heterostructures as a robust platform compatible with scalable fabrication, providing a pathway toward stable and tunable infrared nanophotonic and optoelectronic devices.
Read the full abstract ▾
All authors Yuanchen Chi, Dongxu Di, Michael Fralaide, Jigang Wang, Zhe Fei
Statistical Mechanics
Transport interpretation of entanglement Hamiltonian cumulants in integrable quantum quenches
Riccardo Travaglino and Pasquale Calabrese
We study the dynamics of the cumulants of the
entanglement Hamiltonian in interacting integrable models following global
quantum quenches. Building on recent results based on space-time duality, we show that these cumulants are exactly given by the cumulants of currents of suitable conserved charges evaluated in the macrostate selected by the initial state. This establishes a direct connection between
entanglement dynamics and transport, providing a transport counterpart to the quasiparticle picture that successfully describes the
evolution of the von Neumann
entropy. In the free-
fermion and conformal limits, our results reduce to the difference between the current cumulants carried by right- and left-moving excitations, recovering previously known expressions. In interacting integrable models, where a decomposition into independent right and left movers is no longer meaningful at the operator level, a similar structure survives at the level of the
entanglement spectrum, yielding a unified description of
entanglement Hamiltonian fluctuations across free, conformal, and interacting integrable systems.
Read the full abstract ▾
Strongly Correlated Electrons
Approximating thermodynamic equilibrium observables of quasi one-dimensional magnetic molecules and chains by thermal DMRG - a user perspective
L. Horstmann and J. Schnack
Density
matrix renormalization group methods or tensor network methods in general can not only be used to determine ground states but also to evaluate thermal
equilibrium properties. Although convergence is superior for one-dimensional
quantum spin systems with nearest neighbor exchange and open boundary conditions, the hope is that these methods can as well be employed to approximate
magnetic observables of
magnetic molecules with more complex interaction patterns. Here, we assume the position of a user and study the accuracy that can realistically be achieved for several archetypical quasi one-dimensional structures using the TenPy suite. In our study, we aim at systems that are too large for exact diagonalization or Krylov space methods.
Read the full abstract ▾
Materials Science
Interface-Controlled Defect Engineering in TiN/TaN Superlattices for Enhanced Hardness and Fracture Toughness
Zecui Gaoa, Qimin Wang, Julian Buchinger et al. (+6 more)
TiNTaN superlattice coatings were designed to investigate how atomic-scale interface chemistry and defect-stabilized TaN layers govern hardness and fracture toughness. Guided by first-principles predictions identifying TaN-based layers as more damage tolerant than TiN, coherent superlattices with a bilayer period of 6 nm were synthesized by reactive magnetron sputtering and interfacially doped with C, B, or Si. Structural and chemical analyses reveal coherent fcc architectures with well-defined interfaces. Si segregates preferentially to the interfaces while incorporating into both TiN and TaN, whereas C and B predominantly diffuse into the TaN layers, modifying coherency strain, bonding, and defect populations. Consequently, hardness increases from 34 GPa for the undoped superlattice to 41 GPa for the Si-doped architecture, whereas fracture toughness increases from 2.8 to 4.0 MPam0.5 for the B-doped superlattice. First-principles calculations show that vacancy-stabilized TaxNy enhances elastic compliance and elastic contrast rather than intrinsic toughness, while the additional toughening induced by B indicates localized defect-assisted energy dissipation at chemically engineered interfaces. Thus, Si maximizes interface strengthening, whereas B provides the most favourable hardness-toughness balance while preserving high hardness, 38 GPa. These findings establish interface chemistry as an additional design parameter for tailoring the mechanical performance of ceramic nitride superlattices.
Read the full abstract ▾
All authors Zecui Gaoa, Qimin Wang, Julian Buchinger, Nikola Koutna, Marcus Hans, Zaoli Zhang, Jochen Schneider, Daniel Primetzhofer, Paul Heinz Mayrhofer
Superconductivity
Disorder-tuned crossing of monopole and conventional pairing instabilities in multi-Weyl semimetals
Enrique Muñoz and Rodrigo Soto-Garrido
We study how non-
magnetic impurity scattering affects the emergence and possible coexistence of pairing instabilities in a two-node multi-Weyl semimetal. Within an explicitly specified projected impurity kernel—valley diagonal and momentum independent across each Fermi pocket, the leading behaviour of non-
magnetic disorder in the small-pocket window $q^{\max}_{\rm intra}\xi_{\rm dis}\ll1\ll|2\mathbf Q|\xi_{\rm dis}$, treated at leading order in Born and Abrikosov–Gor'kov theory—quenched disorder tunes the leading pairing instability from a topologically nontrivial monopole channel to a conventional ($s$-wave) one, extending our earlier clean-system analysis into the disordered regime. A Born self-energy calculation in the chiral band basis then gives: (i) a band-isotropic conventional channel that is Anderson protected against intra-node scalar disorder ($\eta_s=1$), introduced phenomenologically at the projected-band level; solving the competition for arbitrary $\eta_s$ yields the crossing criterion $(1-\eta_s)/(1-\eta_m)<T_{c0}^{(s)}/T_{c0}^{(m)}$, so the mechanism tolerates substantial loss of conventional-channel protection; and (ii) a rank-one monopole sector fixing $f_m$ as the exact eigenfunction with $\eta_m(J)=1/(J+2)$, exact given that kernel. The crossing location in $\Gamma_N/T_{c0}^{(m)}$ is set by $\eta_m(J)$, $\eta_s$, and $r=T_{c0}^{(s)}/T_{c0}^{(m)}$. From the clean projected BdG
Hamiltonian the pure monopole nodes carry Berry charge $\pm J$, distinct from the gapped conventional solution; the clean nodal thermodynamics is charge-dependent, $N_{\rm SC}(E)\propto E^{2/J}$ and $C\propto T^{1+2/J}$, and the residual density of states shows a threshold only for $J=1$. The crossing lies in the moderately metallic regime, $\mu/\Gamma_N\simeq11$–$14$ for the illustrative $T_{c0}^{(m)}/\mu=0.133$ used in the figures.
Read the full abstract ▾
Mesoscale and Nanoscale Physics
Intervalley Magnetotrions Tunable by Electric and Magnetic Fields in Buckled Two-Dimensional Materials
Roman Ya. Kezerashvili, Shalva M. Tsiklauri and Anastasia Spiridonova
We develop a theoretical framework for intervalley magnetotrions in buckled two-dimensional materials, including silicene, germanene, and stanene, subjected to perpendicular electric and
magnetic fields. Within the effective-mass approximation, the three-particle Schrödinger equation is formulated with the Rytova–Keldysh interaction potential and analyzed in the high-
magnetic-field regime. We demonstrate that intervalley trions with equal electron and hole effective masses constitute an exceptional case for which the center-of-mass and internal motions separate exactly. The center-of-mass motion is governed by a two-dimensional harmonic-oscillator
Hamiltonian, leading to quantized Landau states whose energies form electrically tunable Landau surfaces controlled by the
magnetic field and the electric-field dependence of the carrier effective masses. The internal motion is investigated by solving the three-body Schrödinger equation within the framework of the hyperspherical harmonics method. Numerical calculations reveal that the trion binding energy increases monotonically with both
magnetic and electric fields owing to the combined effects of
magnetic confinement and electric-field-induced enhancement of the effective masses. The strongest binding is obtained for silicene, followed by stanene and germanene. The present work provides a unified description of both the collective center-of-mass motion and the internal dynamics of magnetotrions in Xene monolayers, demonstrating that both degrees of freedom can be independently manipulated by external electric and
magnetic fields.
Read the full abstract ▾
Soft Condensed Matter
Phoretic interactions in two-medium wedge geometries
Abdallah Daddi-Moussa-Ider
We investigate the diffusiophoretic motion of a chemically isotropic active colloid in a three-dimensional wedge formed by two distinct fluid media, in the limit of vanishing Péclet and Reynolds numbers. The concentration field is obtained using the
Fourier-Kontorovich-Lebedev transform, yielding an exact representation for arbitrary wedge opening angles and interfacial contrasts. We introduce the interfacial parameter $\Gamma=(1-\lambda\ell)/(1+\lambda\ell)$, where $\lambda$ denotes the diffusivity contrast and $\ell$ the solute partition coefficient. For $\Gamma=\pm1$ and commensurate wedge angles, the solution reduces to finite image constructions, with distinct structures for even and odd commensurability. The general solution also recovers the planar-interface and semi-infinite-interface limits. The leading-order translational phoretic velocity is derived from the concentration field, revealing a strong interplay between wedge geometry and interfacial properties that governs both the magnitude and direction of particle motion. This work provides a framework for understanding and controlling phoretic transport in confined multiphase environments and offer a basis for extensions to finite-size geometries and mixed fluid–fluid and solid boundary conditions. Our results may find applications in the control of active-particle transport in confined multiphase environments, where interfacial properties and geometry can be exploited to tune phoretic motion.
Read the full abstract ▾
Mesoscale and Nanoscale Physics
Floquet engineering of spin-valley selective transport in jacutingaite
Otman Bouladiane, Kamal Azaidaoui, Clarence Cortes et al. (+2 more)
We study electron transport through a monolayer jacutingaite (Pt$_2$HgSe$_3$) tunnel junction in which only the barrier is irradiated by off-resonant circularly polarized light, while the leads remain undriven. In the high-frequency regime, the driven barrier reduces to an effective static Dirac
Hamiltonian with a
photon-dressed, valley-dependent mass term. A staggered sublattice potential $V_z$ and a substrate-induced exchange field $m_s$ provide additional tunable mass terms. Using scattering theory, we compute
spin- and valley-resolved transmission and reflection, as well as the Landauer conductance.
Photon dressing shifts the barrier {Dirac masses} with opposite signs in the ($\boldsymbol{K}, \boldsymbol{K}'$) valleys and induces a splitting of the propagation thresholds. The finite barrier then produces channel-dependent Fabry–Pérot-type interference through the phase $q_x^{\eta s_z}L$. We find broad parameter windows with near-perfect valley filtering ($|P_v|\simeq 100\%$) and substantial
spin polarization ($|P_s|\sim 70\%$). The dominant
spin and valley polarizations can be switched by tuning the drive amplitude $A_0$, $V_z$, and~$m_s$.
Read the full abstract ▾
All authors Otman Bouladiane, Kamal Azaidaoui, Clarence Cortes, David Laroze, Ahmed Jellal
Materials Science · Cross-listed from math.NA
Randomized Block Davidson Eigensolvers for Plane-Wave Density-Functional Theory
Moritz Gubler, Taejun Park, Augustin Bussy et al. (+4 more)
Iterative diagonalization is the dominant cost of plane-wave density-functional theory (DFT), with search-space orthogonalization scaling particularly quickly with problem size and the number of target states. We present a randomized block Davidson-type eigensolver that replaces Euclidean orthogonalization with randomized Gram-Schmidt in a sketched inner product, requiring only a single pass over the basis while keeping its conditioning bounded independently of the input vectors. This modification changes only the Rayleigh-Ritz step, which becomes a definite generalized Hermitian eigenproblem. Ritz extraction remains exact, preserving true Ritz pairs and the interlacing property that makes each band energy an upper bound on the true one. The method is implemented in mixed precision for CPUs and GPUs from a single Julia code, interfaces
matrix-free with DFTK, and is released in the open-source RandESC library. On sparse test problems with a fixed number of eigenpairs, the sketched solver overtakes its deterministic counterpart beyond
matrix dimensions of about $2\times 10^4$ and is $25\%$ faster at $5\times 10^5$. In full self-consistent field DFT calculations, however, both Davidson variants outperform the locally optimal block preconditioned conjugate gradient (LOBPCG) reference only by $5$ to $11\%$ in total time, while the additional benefit of sketching is limited. As the number of requested states grows with system size, orthogonalization savings are offset by the generalized eigenproblem. Therefore, the regime in which sketching pays off is set by how the number of wanted states scales with the problem dimension, not by the eigensolver as such.
Read the full abstract ▾
All authors Moritz Gubler, Taejun Park, Augustin Bussy, Johannes Laute, Nicola Marzari, Iurii Timrov, Laura Grigori
Statistical Mechanics
Dynamic quantum phase transitions in the two-leg Creutz ladder with long-range hopping
J. A. da Silva and J. C. Xavier
In this work, we investigate
quantum quenches in the two-leg Creutz model with long-range hopping, where the hopping amplitudes decay with distance as a power law characterized by an exponent $\nu$ and have a finite range $D$. We first obtain the exact solution of a generic two-band model in momentum space. This allows us to compute the Loschmidt amplitude and, consequently, the dynamical free energy $f(\texttt{t})$ of the two-band model. We also show how to determine the Yang-Lee Fisher (YLF) zeros by solving a nonlinear equation. We demonstrate that the two-leg Creutz model in momentum space is a special case of the generic two-band model. Using these results, we identify the non-analyticities in the dynamical free energy $f(\texttt{t})$ at critical times $\texttt{t}_{c}$. We find that the number of nontrivial critical times $N_{s}$ depends on both $\nu$ and $D$. In particular, we show that for small $\nu$ and large $D$ the critical times become increasingly dense, leading, in the appropriate regime, to non-analyticities at an increasingly dense set of times—similar to what was observed by Xavier and Hoyos [Phys. Rev. B, $\textbf{108}$, 214303 (2023)] in the Su-Schrieffer-Heeger (SSH) model with long-range hopping terms.
Read the full abstract ▾
Materials Science
Structure-Agnostic Prediction of the Electronic Density of States with a Chemical Language Model
Ivan D. Rubtsov, Ivan V. Dudakov and Vadim V. Korolev
The electronic density of states (DOS) is conventionally computed from a relaxed
crystal structure, which is unavailable for compounds that have been neither synthesized nor cataloged. Here we introduce DOSSIER ($\textbf{D}$ensity $\textbf{o}$f $\textbf{S}$tates from $\textbf{S}$to$\textbf{i}$chiometry with $\textbf{E}$ncoder $\textbf{R}$epresentations), a chemical
language model that maps elemental composition directly to this spectrum. The encoder is pretrained by cross-modal knowledge
distillation from a universal machine-learning interatomic potential; the transfer lowers the error by 11% when only 1,000 training examples are available. On the Mat2Spec
benchmark, DOSSIER reaches a mean absolute error of 3.76 states eV$^{-1}$ against 3.64 for the best structure-aware model; on an extended Materials Project
dataset, the predicted spectra yield band gaps and $\textit{d}$-band descriptors with useful accuracy. Screening 11,977 binary and 13,251 five-component high-
entropy alloy compositions for a $\textit{d}$-projected DOS resembling that of NiPt$_{3}$ places known oxygen reduction electrocatalysts near the top of the ranking.
Read the full abstract ▾
Mesoscale and Nanoscale Physics · Cross-listed from physics.optics
AlGaAs nanowires as a universal platform for GaAs, InGaAs, and InAs quantum dots
Rohan Radhakrishnan, Rodion Reznik, Gilles Patriarche et al. (+5 more)
Optical
quantum dots (QDs) are central to photonic
quantum technologies, with fabrication approaches tailored to different spectral ranges. A key challenge, however, is the realization of a unified platform$\unicode{x2014}$a single growth method combined with a host material offering a designable architecture$\unicode{x2014}$enabling wavelength tunability across the full emission range and co-integration of multiple
quantum dots. Here, we introduce AlGaAs nanowires as a universal host for GaAs, InGaAs, and InAs QDs. Building on our previous demonstration of high-quality GaAs QDs, we realize InGaAs QDs with tunable emission by varying the growth duration from 2 to 5 s, achieving emission at 780 and 920 nm. We further showcase the platform's versatility for multi-
quantum-dot devices by co-integrating two InGaAs QDs, as well as GaAs and InGaAs QDs within a single nanowire. Finally, we initiate a first step toward pure InAs QDs by growing a pristine InAs segment on AlGaAs nanowires, demonstrating material compatibility.
Read the full abstract ▾
All authors Rohan Radhakrishnan, Rodion Reznik, Gilles Patriarche, Igor Ilkiv, Konstantin Kotlyar, Anna Andreeva, George Cirlin, Nika Akopian
Disordered Systems and Neural Networks
Disorder-induced conducting edges on Kagomé lattice
A. Chmeruk, D. Jones and L. Chioncel
Within a cluster extension of the coherent potential approximation, disorder averaging generates a non-local self-energy that renormalizes both diagonal and off-diagonal hopping terms of the non-interacting Kagome-
lattice Hamiltonian. These renormalizations (of both nearest- and next-nearest-neighbor hopping amplitudes) drive the system between two topologically trivial insulating states through an intermediate gapless phase characterized by conducting edge modes over a broad range of impurity concentrations. Our results demonstrate that multiple-scattering effects alone can generate emergent effective
spin-orbit interactions and qualitatively modify the edge spectrum of disordered Kagome systems.
Read the full abstract ▾
Materials Science
Plastic Relaxation without Dislocations in $\beta$-Ga$_2$O$_3$ Heteroepitaxy: A Structural Peculiarity of Ga$_2$O$_3$ Polymorphs
I. Bertoni, A. Marzegalli, A. Ugolotti et al. (+3 more)
$\beta$-Ga$_2$O$_3$ grows as three-dimensional islands on mismatched c-plane sapphire, often on a thin $\alpha$-Ga$_2$O$_3$ wetting layer, and eventually forms a continuous film by island coalescence. Experiments reveal the $\beta$ film to be relaxed. Surprisingly no dislocations are observed, suggesting an unusual plastic relaxation path. We reveal the key mechanisms underlying this process by combining density functional theory, continuum nucleation theory, and molecular dynamics simulations. Plastic relaxation occurs through rearrangement of the Ga atoms beneath the oxygen plane shared by both the wetting layer and the (-201) $\beta$-Ga$_2$O$_3$ structures. A local $\alpha$ to $\beta$-relaxed phase transition is thus realized within a single plane, allowing full relaxation of the $\beta$-Ga$_2$O$_3$ island.
Read the full abstract ▾
All authors I. Bertoni, A. Marzegalli, A. Ugolotti, R. He, F. Djurabekova, L. Miglio
Strongly Correlated Electrons
Anomalous magnetocaloric effects in the quasi-one-dimensional antiferromagnet BaCo$_2$V$_2$O$_8$
Jiahao Yang, Chao Dong, Xinlong Shi et al. (+8 more)
We investigate the transverse-field thermodynamics of the quasi-one-dimensional Ising-like antiferromagnet BaCo$_2$V$_2$O$_8$, whose tilted screw-chain geometry and anisotropic Landé $g$ tensor generate spatially modulated Zeeman couplings. Angle-resolved magnetocaloric-effect (MCE) measurements reveal a high-field temperature minimum near the transverse-field Ising critical field for $H\parallel[110]$ that persists and shifts only weakly upon field rotation. Tensor-network calculations show that the rotation-induced staggered transverse field rapidly lowers the Ising critical field and that the
magnetic Grüneisen ratio changes sign near the high-field temperature minimum, consistent with experiment. Our results establish that a dominant MCE response can persist away from the Ising critical region, suggesting a route to
magnetic cooling by tailoring anisotropic Zeeman-coupling configurations in
quantum magnets.
Read the full abstract ▾
All authors Jiahao Yang, Chao Dong, Xinlong Shi, Zhuo Wang, Tiantian Li, Liusuo Wu, Junfeng Wang, Zhangzhen He, Liang Li, Yongkang Luo, Jianda Wu
Mesoscale and Nanoscale Physics
Electronic cooling of a TiW alloy normal-metal island using Nb-based superconducting tunnel junctions
Joel Hätinen, Renan Pires Loreto, Arvind Kumar et al. (+2 more)
TiW thin films remain non-superconducting down to millikelvin temperatures and are compatible with large-scale CMOS manufacturing, making them attractive for cryogenic and
quantum tunnel-junction devices, such as normal-metal-
insulator-
superconductor (NIS) thermal sensors and electron refrigerators. We demonstrate significant electronic cooling of a TiW-based normal-metal island and electron thermometry by using TiW-Al-AlOx-Nb NIS tunnel-junction stacks. The NIS thermometer enables local electron temperature measurements from 0.5 to 8.32 K. NIS cooling is observed between 0.6 and 3.5 K, with maximum absolute and relative temperature reductions of 217 mK and 27%, respectively. Calculations using tunnel-junction parameters obtained independently from current-voltage fits reproduce the measured optimum-voltage scale, which lies substantially below the ideal low-temperature prediction.
Read the full abstract ▾
All authors Joel Hätinen, Renan Pires Loreto, Arvind Kumar, Jani Taskinen, Mika Prunnila
Quantum Gases · Cross-listed from quant-ph
Tunable-Size Unruh-DeWitt Detector in a Multimode Cavity
Simon Brunner, Farokh Mivehvar, Helmut Ritsch et al. (+1 more)
Quantum simulators based on Bose-Einstein condensates (BECs) provide a powerful platform to study relativistic
quantum-field phenomena in the lab and in particular emulate relativistic analog particle detectors. However, such detectors typically couple to excitations beyond the acoustic
phonon regime, so that the nonlinear Bogoliubov dispersion introduces corrections that cause the effective relativistic description to break down. We propose to overcome this limitation using an intrinsically momentum-selective Unruh-DeWitt detector model in which a tweezer-trapped atom couples to the condensate through a multimode optical cavity. Although the atom is effectively pointlike, the cavity-mediated interaction kernel causes it to sample density fluctuations over a controllable finite region of the BEC equivalent to a finite-size detector. The effective detector size is tunable via the cavity mode structure determining a controllable momentum cutoff that filters out nonphononic excitations. We analytically calculate the response of such a detector for uniform linear acceleration and uniform circular motion and show that this momentum selectivity can enhance the signal at experimentally accessible accelerations. Compatible with existing cavity-QED platforms our scheme thus provides a versatile setting for analog
quantum-field measurements or relativistic
quantum-information protocols.
Read the full abstract ▾
All authors Simon Brunner, Farokh Mivehvar, Helmut Ritsch, Arkadiusz Kosior
Materials Science
A colossal dielectric response of Bi1-xSmxFeO3 nanopowders
Vladyslav O. Kolupaiev, Olexander S. Pylypchuk, Vladimir N. Poroshin et al. (+6 more)
The dielectric permittivity of the pressed powder samples of Bi1-xSmxFeO3, with Sm content "x" varying in the range 0 - 0.2, has been investigated in the temperature range from 20 to 400 C and the frequency range from 100 Hz to 100 kHz. We have shown that the Sm content impacts significantly the real and imaginary parts of effective dielectric permittivity, which have expanded diffuse maxima with a colossal magnitude up to 105 (for the real part) and up to 108 (for the imaginary one) at temperatures 300 - 400 K. Analysis of experimental data carried has shown that both the real and imaginary parts of effective dielectric permittivity may be comprehensively explained by considering a complex interplay of a diffuse ferroelectric-paraelectric phase transition and the Maxwell-Wagner-Sillars effects, which emerge from the formation of spatial charges at interfaces between nanograins and at the ferroelectric nanoparticle-air interface. Processing of experimental data for the real and imaginary parts of the effective dielectric permittivity within effective medium approach allows us to separate and analyze the colossal dielectric response of the nanoparticles itself. The main trends followed from experiments are supported by the theoretically simulated dependences, which reveal correlations between the temperature behavior of dielectric properties and phase state of the Bi1-xSmxFeO3 nanoparticles.
Read the full abstract ▾
All authors Vladyslav O. Kolupaiev, Olexander S. Pylypchuk, Vladimir N. Poroshin, Denis O. Stetsenko, Ihor V. Fesych, Lesya D. Demchenko, Eugene A. Eliseev, Victor V. Vainberg, Anna N. Morozovska
Mesoscale and Nanoscale Physics · Cross-listed from quant-ph
Towards Stirling cooler operable single-photon sources based on low-noise GaAs quantum dots
Maximilian Aigner, Jana Schlücking, Eva Schöll et al. (+15 more)
For photonic
quantum technology applications, sources capable of emitting
photons with indistinguishability close to unity are essential. Ideally, these sources should not require demanding cooling systems. Here, we present temperature-dependent two-
photon-interference measurements on
photons produced by the radiative decay of the negative trion in a low-noise GaAs
quantum dot, which are in quantitative agreement with theoretical calculations accounting for carrier-
phonon interactions and coupling to excited states. While at at the lowest explored temperatures the emission linewidth reaches values only 6(2) % above the
Fourier limit and the indistinguishability I between subsequently emitted
photons reaches 0.966(6), the latter drops to 0.05(4) at 55 K. We show that this loss can be explained with the coupling with energetically close excited trion states and suggest that the
photon indistinguishability at elevated temperatures can be increased by employing Purcell enhancement of the emission rate or by increasing the energy separation of the excited states. Using cavity-enhanced emission, we experimentally verify the first route and demonstrate an improvement in
photon indistinguishability from 0.314(25) to 0.80(3) at 32 K, which - to our knowledge - is the highest reported value at such temperature.
Read the full abstract ▾
All authors Maximilian Aigner, Jana Schlücking, Eva Schöll, Christian Weidinger, Gabriel Undeutsch, Ievgen Brytavskyi, Thomas Oberleitner, Tobias Maria Krieger, Ailton Jose Garcia Junior, Melina Peter, Thomas K. Bracht, Michał Gawełczyk, Saimon Filipe Covre da Silva, Santanu Manna, Yusuf Karli, Gregor Weihs, Doris E. Reiter, Armando Rastelli
Strongly Correlated Electrons
Altermagnetic Anomalous Hall Effect and Spin–Edge-Locked Chiral Modes in a Modified Kane–Mele–Hubbard Model
Mohsen Hafez-Torbati and Alireza Qaiumzadeh
We establish a correlation-driven route to the altermagnetic anomalous Hall effect (AHE) and its associated
spin–edge-locked edge states in a modified Kane–Mele–Hubbard model. Using dynamical mean-field theory (DMFT), we show that, at half-filling, increasing the Hubbard interaction drives the system from a metallic paramagnetic phase hosting antichiral edge states into an insulating in-plane Néel-type antiferromagnetic phase, in which a residual antiunitary
symmetry forbids the AHE. Hole doping induces a
spin-flop transition to an out-of-plane Néel-type antiferromagnetic phase, thereby breaking this
symmetry and generating a finite anomalous Hall conductivity that persists into the strongly correlated regime. Distinct from a conventional
spin-polarized Hall response in ferromagnets, the altermagnetic AHE receives equal and additive contributions from the two
symmetry-related
spin sectors and is accompanied by
spin–edge-locked chiral states. Our results demonstrate that carrier doping and
spin-rotationally invariant Hubbard interactions are sufficient to realize the altermagnetic AHE, without invoking an explicitly Ising-like interaction, and provide a realistic microscopic route toward its realization in correlated transition metal dichalcogenides monolayers.
Read the full abstract ▾
Statistical Mechanics
Emergence of Stigmergic Transport in Granular Environments
F.Wéry, F.N. Pinan Basualdo, B. Gorissen et al. (+1 more)
We show that stigmergic path formation emerges in a deformable environment through the interplay between environmental
memory and geometrical crowding. Using experiments with robotic random walkers together with a minimal
stochastic model, we demonstrate the onset of persistent self-reinforced transport pathways above a critical packing fraction $\phi_c$, where environmental
memory enhances walker mobility. As the jamming transition $\phi_J$ is approached, increasing crowding progressively suppresses this transport enhancement despite the persistence of environmental
memory. The resulting non-monotonic behavior reveals an optimal transport regime well below jamming. More generally, our work establishes how active
agents can collectively build transport networks through purely mechanical interactions with a deformable substrate.
Read the full abstract ▾
All authors F.Wéry, F.N. Pinan Basualdo, B. Gorissen, N.Vandewalle
Statistical Mechanics
Exact autoregressive sampling of planar Ising spin glasses via the Kac–Ward theory
Jing Liu, Tao Chen, Tianrui Che et al. (+3 more)
Exact sampling from the Boltzmann distribution of
spin glasses remains an outstanding challenge: Markov chain Monte Carlo methods suffer from critical slowing down and metastable trapping, while modern neural autoregressive samplers such as variational autoregressive networks are approximate and, in the absence of exact reference samples, cannot be rigorously benchmarked. Here we present an exact autoregressive sampling
algorithm for planar Ising
spin glasses based on the Kac–Ward theory. Under the chain-rule factorization, sequentially fixing
spins induces boundary-localized external fields, which destroy the zero-field structure required for exact evaluation. By encoding these fields with a planarity-preserving auxiliary
spin construction, the conditional partition functions are mapped to an extended zero-field Ising model and exactly evaluated using the Kac–Ward determinant formula. The method generates strictly independent and identically distributed samples with exact normalized likelihoods at a computational cost of $\mathcal{O}(N^{5/2})$ for $N$
spins, thereby providing an exact baseline for benchmarking neural autoregressive samplers.
Read the full abstract ▾
All authors Jing Liu, Tao Chen, Tianrui Che, Lei Wang, Youjin Deng, Pan Zhang
Soft Condensed Matter
Conformation-Mediated Kinetics of Polymer Chain Scission under Tension
Jie Zhu and Laurence Brassart
Chain scission is a key molecular process underlying damage and fracture in
polymer networks. In this Letter, we develop a statistical-mechanical framework for predicting chain-scission kinetics while accounting for three-dimensional (3D) conformational fluctuations. Within transition-state theory, scission is formulated as a multichannel first-rupture problem, with bond-specific rates governed primarily by self-consistent potentials of mean force. In the freely jointed limit, the additional 3D configurational freedom enhances rupture relative to the collinear 1D reference. Finite bending stiffness introduces orientational correlations that can reverse this enhancement and, at high stiffness, reduce rupture rates by orders of magnitude. These correlations also make rupture bond-position dependent, with higher rates near the chain ends and a common interior rate. For sufficiently long chains, the interior contribution dominates, yielding linear scaling of the chain-scission rate with chain length. These molecularly resolved rates provide physically grounded inputs for future network-scale models of
polymer damage and fracture.
Read the full abstract ▾