Персона: Грудинина, Анна Михайловна
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Dark and thermal reservoir contributions to polariton sound velocity
Finite-temperature Hartree-Fock-Bogoliubov theory for exciton-polaritons
Microcavity exciton-polaritons, known to exhibit nonequilibrium Bose condensation at high critical temperatures, can also be brought in thermal equilibrium with the surrounding medium and form a quantum degenerate Bose-Einstein distribution. It happens when their thermalization time in the regime of positive detunings-or, alternatively, for high-finesse microcavities-becomes shorter than their lifetime. Here we present the self-consistent finite-temperature Hartree-Fock-Bogoliubov description for such a system of polaritons, universally addressing the excitation spectrum, momentum-dependent interactions, condensate depletion, and the background population of dark excitons that contribute to the system's chemical potential. Employing the derived expressions, we discuss the implications for the Bogoliubov sound velocity, confirmed by existing experiments, and define the critical temperatures of (quasi)condensation and the integral particle lifetime dependencies on the detuning. Large positive detunings are shown to provide conditions for the total lifetime reaching nanosecond timescales. This allows realization of thermodynamically equilibrium polariton systems with Bose-Einstein condensate forming at temperatures as high as tens of Kelvin.
ОПРЕДЕЛЕНИЕ КОНСТАНТЫ ТУННЕЛИРОВАНИЯ НА ДЕФЕКТЕ ДЛЯ БОЗЕ-КОНДЕНСАТОВ В ГЕОМЕТРИИ РАЗОРВАННОГО КОЛЬЦА
Работа посвящена оценке константы туннелирования для кольцевых бозе-конденсатов с барьером в рамках формализма энергетического функционала Гросса–Питаевского. Получены аналитические выражения в предельных случаях узкого и широкого барьеров. Для оценки константы туннелирования проводится фитирование численной зависимости значения энергетического функционала от разности фазы на барьере с помощью параметров потенциала вида «стиральной доски».
Enhanced Polariton Interactions in Suspended WS2 Monolayer Microcavity
Collective excitations of a bound-in-the-continuum condensate
Spectra of low-lying elementary excitations are critical to characterize properties of bosonic quantum fluids. Usually these spectra are difficult to observe, due to low occupation of non-condensate states compared to the ground state. Recently, low-threshold Bose-Einstein condensation was realised in a symmetry-protected bound state in the continuum, at a saddle point, thanks to coupling of this electromagnetic resonance to semiconductor excitons. While it has opened the door to long-living polariton condensates, their intrinsic collective properties are still unexplored. Here we unveil the peculiar features of the Bogoliubov spectrum of excitations in this system. Thanks to the dark nature of the bound-in-the-continuum state, collective excitations lying directly above the condensate become observable in enhanced detail. We reveal interesting aspects, such as energy-flat parts of the dispersion characterized by two parallel stripes in photoluminescence pattern, pronounced linearization at non-zero momenta in one of the directions, and a strongly anisotropic velocity of sound.
Path integral approach to bosonization and nonlinearities in exciton-polariton systems
К ВОПРОСУ О БОЛЬШИХ НЕЛИНЕЙНОСТЯХ В ЭКСИТОН-ПОЛЯРИТОННЫХ СИСТЕМАХ НА ОСНОВЕ ДИХАЛЬКОГЕНИДОВ ПЕРЕХОДНЫХ МЕТАЛЛОВ
Работа посвящена изучению бозонизации в бозон-фермионных смесях, а именно в электрон-дырочно-фотонных системах с сильной связью. Изучено влияние наличия фотонного поля и темных экситонных состояний на взаимодействие на примере экситонных поляритонов в дихалькогенидах переходных металлов.