arXiv subjects

A. I. Veretennikov

Publications and source records attributed to A. I. Veretennikov.

4 recordsLinked to original sources

arXiv2026

Self-balancing luminescence kinetics of charged excitons in WS$_2$ monolayer

Two-dimensional tungsten-based transition metal dichalcogenides exhibit a rich emission spectrum with distinct lines of exciton and biexciton states, neutral and charged, which are typically considered as independent entities. Here, we present a study of the emission kinetics of a WS$_2$ monolayer, demonstrating that these states together form a single interacting ensemble, with their population and depletion mutually coordinated with temperature. Dark trions make a long-lived contribution to the bright trion on a time scale of 200-300 picoseconds, and replenishment from dark states promotes intense luminescence of charged biexcitons. The developed self-consistent rate equation model reproduces the temperature dependence of the kinetics well, opening the way to controlling exciton states in such materials.

cond-mat.mes-hall↗

arXiv2026

Purcell enhancement in layered InSe on the Mie-resonant silicon nitride waveguide

Layered van der Waals semiconductors are promising active materials for nanoscale photonic and optoelectronic devices because their excitonic emission can be integrated with heterogeneous photonic architectures. For on-chip applications, this emission must be efficiently coupled to guided modes, while its recombination dynamics should be controlled by the local photonic environment. Although dielectric waveguides enable such integration, substantial control over radiative recombination generally requires resonant engineering of the local photonic density of states. Resonant dielectric nanostructures provide such control by modifying the photonic environment while preserving compatibility with guided-wave photonic architectures. Here, we demonstrate Purcell-enhanced excitonic emission from a thin InSe flake integrated with a Mie-resonant Si$_3$N$_4$ waveguide. The structure incorporates a resonant nanoparticle array with a resonance that overlaps the InSe PL band, thereby enhancing excitonic coupling to the guided mode. Optical spectroscopy confirms the designed resonance, while micro-photoluminescence measurements reveal enhanced and spectrally selective waveguide-coupled emission. Time-resolved photoluminescence measurements show a threefold shortening of the excitonic decay time relative to planar InSe. Analysis of the decay dynamics using a simple rate-equation model yields an effective Purcell factor of approximately 3 for the dominant out-of-plane excitonic emission channel. These results establish Mie-resonant dielectric waveguides as a compact platform for on-chip control of excitonic recombination in layered semiconductors.

cond-mat.mes-hall↗

arXiv2025

Photoluminescence Features of Few-Layer Hexagonal $α$-In$_2$Se$_3$

Indium (III) selenide is currently one of the most actively studied materials in the two-dimensional family due to its remarkable ferroelectric and optical properties. This study focuses on the luminescent properties of few-layer In$_2$Se$_3$ flakes with thicknesses ranging from 7 to 100 monolayers. To explore the photoluminescence features and correlate them with changes in crystal symmetry and surface potential, we employed a combination of techniques, including temperature-dependent micro-photoluminescence, time-resolved photoluminescence, Raman spectroscopy, atomic force microscopy, and Kelvin probe force microscopy. X-ray diffraction and Raman spectroscopy confirmed that the samples studied possess the $α$-polytype structure. The micro-photoluminescence spectrum consists of two bands, A and B, with band B almost completely disappearing at room temperature. Temperature-dependent photoluminescence and time-resolved measurements helped us to elucidate the nature of the observed bands. We find that peak A is associated with emission from interband transitions in In$_2$Se$_3$, while peak B is attributed to defect-related emission. Additionally, the photoluminescence decay times of In$_2$Se$_3$ flakes with varying thicknesses were determined. No significant changes were observed in the decay components as the thickness increased from 7 to 100 monolayers, suggesting that there are no qualitative changes in the band structure.

cond-mat.mtrl-sci↗

arXiv2024

Stimulated down-conversion of single-photon emission in a quantum dot placed in a target-frequency microcavity

Currently, two optical processes are mainly used to realize single photon sources: deterministic transitions in a semiconductor quantum dot (QD) placed in a microcavity and spontaneous frequency down-conversion in materials with intrinsic nonlinearity. In this work, we consider another approach that combines the advantages of both, such as high power with on-demand generation from QDs and the possibility of frequency tuning from nonlinear sources. For this purpose, we use stimulated frequency down-conversion occurring directly in the QD inside a microcavity designed not to the exciton frequency in the QD but to the target single photon frequency, which is set by the difference between the exciton resonance and the stimulating laser energies. This down-conversion arises from the second-order nonlinear interaction of an exciton (bright heavy-hole or dark) and a light-hole exciton in the stimulating laser field. We present an analytical model for such a down-conversion process and evaluate its efficiency for a widely sought-after single photon source for the telecom C-band (1530-1565 nm). We show that the emission rate of down-converted single photons can approach MHz. At certain conditions, this process is comparable in efficiency to direct emission from an InAs/GaAs QD at 920 nm, which is outside the cavity mode.

cond-mat.mes-hall↗