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## Mean field study of 2D quasiparticle condensate formation in presence of strong decay

QUANTUM. 2023. Vol. 7. Article 1144.

Bose-condensation in a system of 2D quasiparticles is considered in the scope of a microscopic model. Mean-field dynamical equations are derived with the help of the Schwinger-Keldysh formalism and a simple model is proposed which allows to describe key features of condensate formation in systems with various quasiparticle decay rates. By analysing stationary solutions of this equation, we obtain the phase diagram of quasiparticle gas, finding a bistability region in the parameter space of the system. Finally, as an application of our theory, we study the phase diagram of a 2D exciton-polariton system in CdTe microcavity.

Zasedatelev A., Baranikov A., Sannikov D. et al., Nature 2021 Vol. 597 P. 493-498

The recent progress in nanotechnology1,2 and single-molecule spectroscopy3–5 paves the way for emergent cost-effective organic quantum optical technologies with potential applications in useful devices operating at ambient conditions. We harness a π-conjugated ladder-type polymer strongly coupled to a microcavity forming hybrid light–matter states, so-called exciton-polaritons, to create exciton-polariton condensates with quantum fluid properties. Obeying Bose ...

Added: September 27, 2021

Alliluev A., Makarov D., Asriyan N. et al., Physics Letters A 2022 Vol. 453 Article 128492

Dynamics of exciton-polaritonic Bose-Einstein condensate is considered. We construct the stochastic Gross-Pitaevskii equation, where condensate is coupled to the excitonic reservoir in the non-Markovian regime. This equation is utilized for study of condensate formation. It is found that increasing of temperature results in transition from spatially uniform to fragmented pattern with onset of numerous vortices. ...

Added: October 24, 2022

Voronova N. S., Elistratov A. A., Lozovik Y., Physical Review B: Condensed Matter and Materials Physics 2016 Vol. 94 No. July P. 045413

Exciton-photon beats known as polariton Rabi oscillations in semiconductor microcavities are usually excited by short pulses of light. We consider a different pumping scheme, assuming a cw pumping of the Rabi oscillator from an exciton reservoir. We account for the initial pulse of light setting the phase, exciton decay due to exciton-phonon and exciton-exciton scattering, ...

Added: September 14, 2016

Plyashechnik A., Alexey A. Sokolik, Voronova N. et al., Physical Review B: Condensed Matter and Materials Physics 2023 Vol. 108 No. 2 Article 024513

Bose-Fermi systems such as mixtures of electrons with excitons or exciton-polaritons are extensively discussed as candidates to host a variety of intriguing phenomena, including polaron formation, drag effects, supersolidity, and superconductivity. In this paper, assuming the strong-coupling regime between the semiconductor excitons and cavity photons, we develop the many-body theory approach addressing the interplay of ...

Added: August 22, 2023

Grudinina A. M., Kurbakov I. L., Yu. E. Lozovik et al., Physical Review B: Condensed Matter and Materials Physics 2021 Vol. 104 No. 12 P. 125301-1-125301-13

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 ...

Added: September 27, 2021

Shishkov V. Y., Andrianov E. S., Lozovik Y., QUANTUM 2022 Vol. 6 Article 719

The theoretical description of non-equilibrium Bose–Einstein condensate (BEC) is one of the main challenges in modern statistical physics and kinetics. The non-equilibrium nature of BEC makes it impossible to employ the well-established formalism of statistical mechanics. We develop a framework for the analytical description of a non-equilibrium phase transition to BEC that, in contrast to ...

Added: August 25, 2022

Воронова Н. С., Посаженков М. А., Ю. Е. Лозовик, Письма в Журнал экспериментальной и теоретической физики 2017 Т. 106 № 11 С. 718-723

В работе представлено теоретическое описание вихревых решений связанных уравнений типа Гросса-Питаевского в двухкомпонентном бозе-конденсате экситонных поляритонов с учетом зависимости энергии расщепления Раби от плотности экситонной составляющей. Показано, что учет эффекта голубого сдвига приводит к значительному снижению плотностей обеих компонент конденсата. Вычислены пространственные профили экситонов и фотонов в поляритонной системе с учетом нелинейных поправок и энергия ...

Added: November 28, 2017

Воронова Н. С., Ю. Е. Лозовик, Письма в Журнал экспериментальной и теоретической физики 2018 Т. 108 № 12 С. 805-809

Исследуется влияние переменной (координатно-зависимой) эффективной массы частиц на поведение квази-двумерных конденсатов фотонов и экситонных поляритонов в параболической ловушке полупроводниковой оптической микрополости. Показано, что правильный учет зависимости эффективной массы от координаты в операторе кинетической энергии приводит к изменению эффективного потенциала конфайнмента частиц. Для фотонной системы найдены поправки к энергии и волновой функции бозе-конденсата. Для экситонных поляритонов ...

Added: November 2, 2018

Shishkov V., Andrianov E., Zasedatelev A. et al., Physical Review Letters 2022 Vol. 128 No. 12 Article 065301

In this Letter, we give an analytical quantum description of a nonequilibrium polariton Bose-Einstein condensate (BEC) based on the solution of the master equation for the full polariton density matrix in the limit of fast thermalization. We find the density matrix of a nonequilibrium BEC, that takes into account quantum correlations between all polariton states. ...

Added: May 9, 2022

Maximov T., Kurbakov I., Voronova N. et al., Physical Review B: Condensed Matter and Materials Physics 2024 Vol. 108 No. 19 Article 195304

We develop the many-body theory of dipolar exciton-polaritons in an optical microcavity in crossed out-of-plane electric and in-plane magnetic fields. Even for relatively weak fields, we reveal the existence of two minima in the bare lower-polariton dispersion, which give rise to the tunable transition between the polariton Bose-Einstein condensate and that of excitons, produced by ...

Added: August 22, 2023

Voronova N. S., Kurbakov I. L., Lozovik Y., Physical Review Letters 2018 Vol. 121 No. 23-5702 P. 235702-1-235702-6

We propose a way to increase the lifetime of two-dimensional direct excitons and show the possibility to observe their macroscopically coherent state at temperatures much higher than that of indirect exciton condensation. For a single GaAs quantum well embedded in photonic layered heterostructures with subwavelength period, we predict the exciton radiative decay to be strongly ...

Added: December 5, 2018

Cosacchi M., Seidelmann T., Cygorek M. et al., Physical Review Letters 2021 Vol. 127 No. 10 Article 100402

The quantum regression theorem (QRT) is the most widely used tool for calculating multitime correlation functions for the assessment of quantum emitters. It is an approximate method based on a Markov assumption for environmental coupling. In this Letter we quantify properties of photons emitted from a single quantum dot coupled to phonons. For the single-photon ...

Added: September 26, 2021

Fedorov A. K., Kurbakov I. L., Shchadilova Y. E. et al., Physical Review A: Atomic, Molecular, and Optical physics 2014 Vol. 90 No. 4 P. 043616

We predict the effect of the roton instability for a two-dimensional weakly interacting gas of tilted dipoles in a single homogeneous quantum layer. Being typical for strongly correlated systems, the roton phenomena appear to occur in a weakly interacting gas. It is important that in contrast to a system of normal to the layer dipoles, ...

Added: December 24, 2014

Asriyan N. A., Kurbakov I. L., Fedorov A. K. et al., Physical Review B: Condensed Matter and Materials Physics 2019 Vol. 99 No. 08-5108 P. 085108-1-085108-8

We consider a bilayer system of two-dimensional Bose-Einstein-condensed dipolar dark excitons (upper layer) and bright ones (bottom layer). We demonstrate that the interlayer interaction leads to a mixing between excitations from different layers. This mixing leads to the appearance of a second spectral branch in the spectrum of bright condensate. The excitation spectrum of the ...

Added: March 8, 2019

Elistratov A., Remizov S., Yurii Lozovik, Physical Review A: Atomic, Molecular, and Optical physics 2020 Vol. 102 No. 4 P. 042224-1-042224-13

Using semion substitution for spin variables we perform an ab initio derivation of effective action for an open quantum two-level system. For this purpose, we introduce, by using the Hubbard-Stratonovich transformation a two-time complex quantum field which average value plays the role of the Green's function for the spin variables. The field thus introduced allows ...

Added: October 30, 2020

Berman O. L., Kezerashvili R., Yurii E. Lozovik, Journal of the Optical Society of America B: Optical Physics 2017 Vol. 34 P. 1649-1658

The condensate density profile of trapped two-dimensional gas of photons in an optical microcavity, filled by a dye solution, is analyzed taking into account a coordinate-dependent effective mass of cavity photons and photon–photon coupling parameter. The profiles for the densities of the superfluid and normal phases of trapped photons in the different regions of the ...

Added: November 28, 2017

Sergeev T. T., Zyablovsky A. A., Andrianov E. S. et al., Scientific Reports 2021 Vol. 11 Article 24054

We demonstrate a new type of non-Hermitian phase transition in open systems far from thermal equilibrium, which can have place in the absence of an exceptional point. This transition takes place in coupled systems interacting with reservoirs at different temperatures. We show that the spectrum of energy flow through the system caused by the temperature ...

Added: January 2, 2022

Kagan M.Yu., Turlapov A. V., J. Phys.: Condens. Matter 2017 Vol. 29 No. 383004 P. 1-22

Physics of many-body systems where particles are restricted to move in two spatial dimensions is challenging and even controversial: On one hand, neither long-range order nor Bose condensation may appear in innite uniform 2D systems at nite temperature, on the other hand this does not prohibit super uidity or superconductivity. Moreover, 2D superconductors, such
as cuprates, ...

Added: June 23, 2017

Cygorek M., Cosacchi M., Vagov A. et al., Nature Physics 2022 Vol. 18 No. 6 P. 662-668

Studies of the dynamics of open quantum systems are limited by the large Hilbert space of typical environments, which is too large to be treated exactly. In some cases, approximate descriptions of the system are possible, for example, when the environment has a short memory time or only interacts weakly with the system. Accurate numerical ...

Added: May 21, 2022

Voronova N., Elistratov A., Yurii Lozovik, Physical Review Letters 2015 Vol. 115 No. 18 P. 186402

We theoretically analyze exciton-photon oscillatory dynamics within a homogenous polariton condensate in presence of energy detuning between the cavity and quantum well modes. Whereas pure Rabi oscillations consist of the particle exchange between the photon and exciton components in the polariton system without any oscillations of their quantum phases, we demonstrate that any non-zero detuning ...

Added: October 22, 2015

Fedorov A. K., Kurbakov I. L., Yu. E. Lozovik, Physical Review B: Condensed Matter and Materials Physics 2014 Vol. 90 No. 16 P. 165430

The formation of the roton-maxon excitation spectrum and the roton instability effect for a weakly correlated Bose gas of dipolar excitons in a semiconductor layer are predicted. The stability diagram is calculated. According to our numerical estimations, the threshold of the roton instability for Bose-Einstein condensed exciton gas with roton-maxon spectrum is achievable experimentally, e.g., ...

Added: December 24, 2014

Sergeev T., Zyablovsky A., Andrianov E. et al., QUANTUM 2023 Vol. 7 Article 982

Exceptional point (EP) is a spectral singularity in non-Hermitian systems. The passing over the EP leads to a phase transition, which endows the system with unconventional features that find a wide range of applications. However, the need of using the dissipation and amplification limits the possible applications of systems with the EP. In this work, ...

Added: August 22, 2023

Sergeev T. T., Zyablovsky A. A., Andrianov E. S. et al., Journal of the Optical Society of America B: Optical Physics 2023 Vol. 40 No. 11 P. 2743-2750

An ultra-strong coupling regime takes place in a compound system when a coupling strength between the subsystems exceeds one tenth of the system eigenfrequency. It transforms into a deep-strong coupling regime when the coupling strength exceeds the system eigenfrequency. In these regimes, there are difficulties with description of relaxation processes without explicit considering of environment ...

Added: August 22, 2023

Demenev A. A., Yaremkevich D. D., Scherbakov A. V. et al., Physical Review B: Condensed Matter and Materials Physics 2019 Vol. 100 No. 10 P. 100301

In the reported experiment, a picosecond strain pulse induces a sharp transition between the steady states in a
bistable cavity-polariton system. The strain pulse of 10-ps duration, generated in the GaAs substrate and injected
into a high-Q GaAs/AlAs microcavity, modulates the exciton resonance energies of the embedded quantum wells
and correspondingly of the polariton resonances. When the microcavity ...

Added: November 20, 2019