arXiv subjects

A. Kudlis

Publications and source records attributed to A. Kudlis.

At least 19 recordsLinked to original sources

arXiv2026

Josephson and Spin Currents in Coupled Polariton Condensates

We analyze particle and spin currents in networks of coupled spinor exciton-polariton condensates arranged as plaquettes and regular polygonal rings. In closed geometries, spin-conserving and TE-TM-induced spin-flip tunnelling combine to generate circulating particle currents, hidden spin counterflows, and bond-dependent spin-current patterns. For the minimal geometries - an equilateral triangle, and a square plaquette - we derive analytical expressions for edge-resolved currents from stationary configurations obtained by energy minimization. We then show how particle, in-plane spin, and out-of-plane spin currents partition the parameter plane and provide direct signatures of the equilibrium phases. Finally, we apply the same current-resolved diagnostics to larger rings, where winding numbers and a branch-invariant common-phase coherence metric organize the resulting phase structure.

cond-mat.mes-hall↗

arXiv2026

Helicity effects in the dynamically assisted Schwinger mechanism

We study vacuum electron-positron pair production in a spatially uniform bichromatic electric field within the quantum-kinetic framework for fermions. The external background models the superposition of two counterpropagating circularly polarized laser pulses and combines a strong slowly varying component with a weak rapidly oscillating one. We analyze the weak-field multiphoton regime, the strong-field tunneling regime, and their combination corresponding to the dynamically assisted Schwinger effect. Our main focus is on helicity-resolved observables. We show that dynamical assistance enhances not only the total yield but also the helicity asymmetry: right- and left-handed electrons preferentially populate opposite momentum half-spaces. Most importantly, within the parameter range considered here, the ratio of the momentum distributions for opposite helicities is governed predominantly by the polar angle with respect to the propagation axis and depends only weakly on the momentum magnitude and azimuthal angle. The corresponding asymmetry becomes more pronounced as the weak-field frequency is increased. These results identify a clear helicity signature of the dynamically assisted Schwinger effect in rotating strong-field backgrounds and provide a compact characterization of the associated helicity-resolved spectra.

hep-ph↗

arXiv2026

Acoustic spin resonance in polariton condensates

We theoretically investigate acoustic spin resonance in a spatially homogeneous spinor polariton condensate. A longitudinal acoustic wave generates a time-periodic strain-induced effective magnetic field acting on the condensate pseudospin. When this field is transverse to the static in-plane linear-polarization splitting, it resonantly drives polarization oscillations. We show that spin-dependent interactions shift the resonance and produce nonlinear line shapes, while gain, reservoir dynamics, and spin relaxation make the response dissipative and history-dependent, producing amplitude hysteresis. In the presence of lifetime anisotropy, the condensate can develop a bifurcated stationary state with finite circular polarization, and a resonant acoustic drive can switch between the corresponding out-of-plane branches. A Zeeman splitting provides an additional conservative knob for tuning the resonance frequency. Our results identify coherent acoustic driving as a route to resonant, nonlinear, and switchable control of polariton pseudospin dynamics.

cond-mat.mes-hall↗

arXiv2026

Vacuum polarization and pair production in time-dependent electric fields: A quantum-kinetic-equation approach

The evolution of the vacuum state in a time-dependent external electric field of arbitrary polarization is investigated within a nonperturbative framework of quantum kinetic equations (QKEs). In our previous work [Phys. Rev. Res. 6, 043009 (2024)], a revised version of the QKEs was derived by using an adiabatic basis constructed from one-particle Hamiltonian eigenfunctions in a spatially homogeneous electric field. In this study, we present an extensive analysis of these equations with particular emphasis on observable quantities. Specifically, we compute momentum-resolved particle yields, the induced electron-positron current, the energy-momentum tensor, and the angular-momentum tensor. We also discuss in detail the charge-renormalization procedure required to remove logarithmic divergences. It is shown that our results are consistent with the previous findings obtained via the Dirac-Heisenberg-Wigner formalism. Our analysis provides a firmer theoretical basis for investigations of nonperturbative effects in strong electric fields.

hep-ph↗

arXiv2025

Classical and single photon memory devices based on polariton lasers

Stimulated scattering of incoherent excitons into an exciton-polariton mode leads to the build-up of a polariton condensate whose polarization is sensitive to a small seeded population that triggers the stimulated process. We show, within a semiclassical stochastic Gross-Pitaevskii model, that this mechanism enables a robust polarization memory operation: the condensate tends to align its Stokes vector with that of the seed and to maintain it for times far exceeding an individual polariton lifetime. Importantly, this single-photon-seeded regime is modeled as an initial weak excitation of the condensate mode. We quantify the memory performance by a classical polarization-alignment metric and find that the seed polarization can remain well preserved on a nanosecond timescale under realistic parameters.

cond-mat.mes-hall↗

arXiv2025

Trion polaron problem in bulk and two-dimensional materials

We develop a microscopic theoryof the trion polaron: a bound state of two electrons and one hole, dressed by longitudinal optical (LO) phonons. Starting from the Frohlich Hamiltonian, which describes the interaction of charged particles with LO phonons in three-dimensional (bulk) and two-dimensional (monolayer) polar crystals, we adopt the intermediate coupling variational approximation of Lee, Low, and Pines, and generalize it for the three-body problem. This yields an effective three-particle Hamiltonian with renormalized electron-electron and electron-hole interactions, similar to those obtained for exciton polaron and bipolaron problems. We compute the binding energies for a family of bulk perovskite materials and several atomic monolayer materials characterized by pronounced polar effects, providing quantitative benchmarks for spectroscopic measurements.

cond-mat.mtrl-sci↗

arXiv2025

Theory of off-diagonal disorder in multilayer topological insulator

We study multilayer topological insulators with random interlayer tunneling, known as off-diagonal disorder. Within the Burkov-Balents model a single Hermitian defect creates a bound state whose energy crosses the middle of the gap in the trivial phase but never in the topological phase; a non-Hermitian defect splits this level yet preserves the same crossing rule, so the effect serves as a local marker of topology. However, the key distinction persists: the bound state crosses zero in the trivial phase but not in the topological phase. Two complementary diagrammatic approaches give matching densities of states for the normal, topological, Weyl and anomalous quantum Hall regimes. Off diagonal disorder inserts bulk states into the gap and can close it: the Weyl phase remains robust under strong disorder, whereas the anomalous quantum Hall phase survives only for weak fluctuations, and the added bulk states shrink the Hall plateau, clarifying experimental deviations. Finally, we analyze edge modes. Uniform disorder shortens their localization length slightly, while Gaussian and Lorentzian disorder enlarge it and in the Gaussian case can even delocalize the edges. Although chirality is maintained, the enhanced overlap permits tunneling between opposite edges and pulls the longitudinal conductance away from its quantized value.

cond-mat.mes-hall↗

arXiv2025

Polarons in two-dimensional polar materials: All-coupling variational theory

We present a detailed and self-contained theoretical study of polarons in two-dimensional (2D) polar materials, which extends the classical macroscopic theory of Fr\"ohlich polarons to the 2D case. The theory is fully determined by experimentally accessible parameters, the static and optical 2D polarizabilities of a monolayer, the frequency of transverse optical phonons, and the effective mass of charge carriers. We define a single dimensionless parameter, which characterizes the coupling of electrons with longitudinal optical phonons, analyze both weak- and strong-coupling regimes, and adopt the Feynman variational path-integral approach for a high-quality interpolation between these limits. Our results provide insight into the ground-state energy and effective mass of polarons in the new generation of 2D polar monolayers.

cond-mat.mes-hall↗

arXiv2025

Vortex structure and intervortex interaction in superconducting structures with intrinsic diode effect

We demonstrate that the intrinsic superconducting diode effect can affect the structure, interactions and dynamics of Abrikosov vortices in non-centrosymmetric superconductor/ferromagnet hybrid structures. The Ginzburg-Landau (GL) theory accounting for the spin-orbit and exchange-field effects predicts a chiral distortion of the superfluid velocity, non-central interaction forces and resulting torque in a vortex-antivortex pair, and anisotropy of the Bean-Livingston barrier. These closed-form results are fully confirmed by time-dependent GL numerical simulations carried out with a fourth-order least-squares finite-difference solver, which captures equilibrium single vortex configuration in realistic mesoscopic geometries. The analysis shows that the cubic gradient term shifts vortex cores by an amount proportional to the in-plane exchange field and simultaneously generates a lateral torque that can rotate entire vortex ensembles, showing how spin-orbit coupling and the exchange field enable breakdown of the vortex-antivortex symmetry in a finite-size sample. By combining transparent analytics with quantitative numerics, the work provides the hallmarks of vortex physics in superconducting structures with an intrinsic diode effect and supplies concrete guidelines for designing non-reciprocal superconducting circuits, fluxonic logic elements, and kinetic-inductance devices.

cond-mat.supr-con↗

arXiv2025

Kardar-Parisi-Zhang universality in optically induced lattices of exciton-polariton condensates

We investigate space-time coherence in one-dimensional lattices of exciton-polariton condensates formed by fully reconfigurable non-resonant optical pumping. Starting from an open-dissipative Gross-Pitaevskii equation with deterministic reservoir kinetics and stochastic condensate noise, we derive a discrete complex-field model that incorporates coherent tunnelling, reservoir-mediated dissipative coupling and gain-saturation non-linearity. Adiabatic elimination of fast density fluctuations reveals a wedge-shaped region in the complex hopping plane where the coarse-grained phase dynamics reduces to the Kardar-Parisi-Zhang (KPZ) equation. By computing high-resolution phase diagrams of the temporal and spatial scaling exponents we pinpoint the boundaries separating the KPZ domain from the Edwards-Wilkinson (EW) regime. Large-scale graphics processing unit (GPU) simulations of chains containing up to $N=2000$ condensates confirm these predictions: inside the wedge the exponents converge to $\beta_{N}=\textbf{0.329}(3)\!\approx\!1/3$ and $\chi_{N}=\textbf{0.504}(4)\!\approx\!1/2$, whereas outside it the dynamics moves away from KPZ and ultimately flows toward the EW fixed point, although finite system size and finite observation time may yield intermediate effective exponents. These results pave the way to the implementation of ultrafast KPZ-simulators based on one-dimensional arrays of exciton-polariton condensates.

cond-mat.mes-hall↗

arXiv2025

Phase transitions induced by resonant light: a phenomenological approach

We present a phenomenological framework to describe a subclass of light-induced phase transitions (LIPTs) in condensed matter systems, specifically those mediated by the resonant generation of excitons. Our approach extends the classical Landau theory by introducing dynamic coupling between the system's order parameter and complex excitonic fields, along with Langevin-type forces that drive the system toward states of minimal free energy. The model is applied in the context of all-optical resonant magnetization switching in two-dimensional magnetic materials, particularly reproducing the experimental findings for reverse magnetization by all-optical means for a monolayer CrI$_3$. Our phenomenological model can be applied to other systems characterized by an order parameter and excitonic fields created through resonant light, offering versatility and potential to guide future experimental and theoretical studies in LIPT phenomena.

cond-mat.mes-hall↗

arXiv2025

Evolution of a twisted electron wave packet perturbed by an inhomogeneous electric field

Laguerre-Gaussian (LG) wave packets, known for their vortex structure and nonzero orbital angular momentum (OAM), are of great interest in various scientific fields. Here we study the nonrelativistic dynamics of a spatially-localized electron LG wave packet interacting with an inhomogeneous external electric field that violates the axial symmetry of the initial wave function. We focus on the analysis of the electron density and demonstrate how it is affected by the external field. Within the first order of perturbation theory, we calculate the electron wave function and reveal that the electric field may significantly alter the wave packet's structure and distort its qualitative form. We demonstrate that due to the interaction with the external field, the degenerate zeros of the initial wave function located on the $z$ axis split into multiple nondegenerate nodes in the transverse plane representing separate single-charge vortices. This mechanism resembles the analogous effects known in topological optics. These findings provide new insights into controlling and manipulating twisted matter beams and into their possible instabilities.

quant-ph↗

arXiv2025

Spin-Meissner effect in systems of coupled polariton condensates

We theoretically investigate the interplay between Zeeman splitting and TE-TM-induced spin-flip tunneling in coupled exciton-polariton condensates systems and its impact on the spin-Meissner effect. We demonstrate that although a single condensate exhibits the effect of full paramagnetic screening via spin-anisotropic interactions, the inter-site spin-flip tunneling can dramatically alter this behavior. The geometry of the system is shown to play a crucial role. In particular, in a dyad, the chemical potential reveals quadratic scaling with the magnetic field. In a triangle, the competition between Zeeman and TE-TM splittings produces a rich phase diagram that features asymmetric polarization states corresponding to both positive and negative magnetic susceptibility. In a square configuration, the symmetry of the network can restore the spin-Meissner effect, so that the condensate emission frequency becomes magnetic field independent in an extended parameter range. These findings not only shed light on the fundamental physics of polariton lattices but also suggest promising avenues for engineering robust spin-controlled photonic devices and polaritonic simulators.

cond-mat.mes-hall↗

arXiv2025

Polarons and Exciton-Polarons in Two-Dimensional Polar Materials

We propose a macroscopic theory of optical phonons, Fr{\"o}hlich polarons, and exciton-polarons in two-dimensional (2D) polar crystalline monolayers. Our theory extends the classical macroscopic formulation of the electron-phonon problem in three-dimensional (3D) polar crystals to the new generation of 2D materials. Similarly to the 3D case, in our approach, the effective electron-phonon Hamiltonian is parametrized solely in terms of macroscopic experimentally accessible quantities -- 2D polarizabilities of the monolayer at low and high frequencies. We derive the dispersion of long wave length longitudinal optical (LO) phonons, which can be viewed as a 2D form of the Lyddane-Sachs-Teller relation, and study the formation of 2D Fr{\"o}hlich polarons by adopting the intermediate coupling approximation. Finally, we apply this approach to excitons in polar 2D crystals and derive an effective potential of the electron-hole interaction dressed by LO phonons. Due to a specific dispersion of LO phonons, polarons and exciton-polarons in 2D materials exhibit unique features not found in their 3D counterparts. As an illustration, the polaron and exciton-polaron binding energies are computed for a representative set of 2D polar crystals, demonstrating the interplay between dimensionality, polarizability of materials, and electron-phonon coupling.

cond-mat.mes-hall↗

arXiv2024

Extended XY model for spinor polariton simulators

The classic lattice XY model is one of the universal models of statistical mechanics appearing in a broad variety of optical and condensed matter systems. One of its possible realizations is a system of tunnel-coupled spinor polariton condensates, where phases of individual condensates play a role of the two-dimensional spins. We show that the account of the polarization degree of freedom of cavity polaritons adds a new twist to the problem, modifying in particular the structure of the ground state. We formulate the corresponding classical spin Hamiltonian, which couples phase and polarization dynamics, and consider several particular geometries, demonstrating the principal differences between the scalar and spinor cases. Possible analog of spin Meissner effect for coupled condensates is discussed.

cond-mat.mes-hall↗

arXiv2024

Semiclassical kinetic equations for composite bosons

We derive semiclassical Boltzmann equations describing thermalization of an ensemble of excitons due to exciton-phonon interactions taking into account the fact that excitons are not ideal bosons but composite particles consisting of electrons and holes. We demonstrate that with a standard definition of excitonic creation and annihilation operators, one faces a problem of the total particle number nonconservation and propose its possible solution based on the introduction of operators with angular momentum algebra. We then derive a set of kinetic equations describing the evolution of the excitonic density in the reciprocal space and analyze how the composite statistics of the excitons affects the thermalization processes in the system.

cond-mat.mes-hall↗

arXiv2024

Quantum beats of a macroscopic polariton condensate in real space

We experimentally observe harmonic oscillations in a bosonic condensate of exciton-polaritons confined within an elliptical trap. These oscillations arise from quantum beats between two size-quantized states of the condensate, split in energy due to the trap's ellipticity. By precisely targeting specific spots inside the trap with nonresonant laser pulses, we control frequency, amplitude, and phase of these quantum beats. The condensate wave function dynamics is visualized on a streak camera and mapped to the Bloch sphere, demonstrating Hadamard and Pauli-Z operations. We conclude that a qubit based on a superposition of these two polariton states would exhibit a coherence time exceeding the lifetime of an individual exciton-polariton by at least two orders of magnitude.

cond-mat.mes-hall↗

arXiv2024

Theory of magnetotrion-polaritons in transition metal dichalcogenide monolayers

Magnetic field is a powerful tool for the manipulation of material's electronic and optical properties. In the domain of transition metal dichalcogenide monolayers, it allows one to unveil the spin, valley, and orbital properties of many-body excitonic complexes. Here we study theoretically the impact of normal-to-plane magnetic field on trions and trion-polaritons. We demonstrate that spin and orbital effects of a magnetic field give comparable contributions to the trion energies. Moreover, as magnetic field redistributes the free electron gas between two valleys in the conductance band, the trion-photon coupling becomes polarization and valley dependent. This results in an effective giant Zeeman splitting of trion-polaritons, in-line with the recent experimental observations.

cond-mat.mes-hall↗