118 research outputs found
Non-equilibrium berezinskii-kosterlitz-thouless transition in driven-dissipative condensate
We study the two-dimensional phase transition of a driven-dissipative system of exciton-polaritons under non-resonant pumping. Stochastic calculations are used to investigate the Berezinskii-Kosterlitz-Thouless–like phase diagram for experimentally realistic parameters, with a special attention to the non-equilibrium features
Kibble-Zurek Mechanism in Driven Dissipative Systems Crossing a Nonequilibrium Phase Transition
The Kibble-Zurek mechanism constitutes one of the most fascinating and universal phenomena in the physics of critical systems. It describes the formation of domains and the spontaneous nucleation of topological defects when a system is driven across a phase transition exhibiting spontaneous symmetry breaking. While a characteristic dependence of the defect density on the speed at which the transition is crossed was observed in a vast range of equilibrium condensed matter systems, its extension to intrinsically driven dissipative systems is a matter of ongoing research. In this Letter, we numerically confirm the Kibble-Zurek mechanism in a paradigmatic family of driven dissipative quantum systems, namely exciton-polaritons in microcavities. Our findings show how the concepts of universality and critical dynamics extend to driven dissipative systems that do not conserve energy or particle number nor satisfy a detailed balance condition
Beyond Gross-Pitaevskii Mean Field Theory
A large number of effects related to the phenomenon of Bose-Einstein
Condensation (BEC) can be understood in terms of lowest order mean field
theory, whereby the entire system is assumed to be condensed, with thermal and
quantum fluctuations completely ignored. Such a treatment leads to the
Gross-Pitaevskii Equation (GPE) used extensively throughout this book. Although
this theory works remarkably well for a broad range of experimental parameters,
a more complete treatment is required for understanding various experiments,
including experiments with solitons and vortices. Such treatments should
include the dynamical coupling of the condensate to the thermal cloud, the
effect of dimensionality, the role of quantum fluctuations, and should also
describe the critical regime, including the process of condensate formation.
The aim of this Chapter is to give a brief but insightful overview of various
recent theories, which extend beyond the GPE. To keep the discussion brief,
only the main notions and conclusions will be presented. This Chapter
generalizes the presentation of Chapter 1, by explicitly maintaining
fluctuations around the condensate order parameter. While the theoretical
arguments outlined here are generic, the emphasis is on approaches suitable for
describing single weakly-interacting atomic Bose gases in harmonic traps.
Interesting effects arising when condensates are trapped in double-well
potentials and optical lattices, as well as the cases of spinor condensates,
and atomic-molecular coupling, along with the modified or alternative theories
needed to describe them, will not be covered here.Comment: Review Article (19 Pages) - To appear in 'Emergent Nonlinear
Phenomena in Bose-Einstein Condensates: Theory and Experiment', Edited by
P.G. Kevrekidis, D.J. Frantzeskakis and R. Carretero-Gonzalez (Springer
Verlag
Dynamical Critical Exponents in Driven-Dissipative Quantum Systems
We study the phase ordering of parametrically and incoherently driven microcavity polaritons after an
infinitely rapid quench across the critical region. We confirm that the system, despite its driven-dissipative
nature, satisfies the dynamical scaling hypothesis for both driving schemes by exhibiting self-similar
patterns for the two-point correlator at late times of the phase ordering. We show that polaritons are
characterized by the dynamical critical exponent z ≈ 2 with topological defects playing a fundamental role
in the dynamics, giving logarithmic corrections both to the power-law decay of the number of vortices and
to the associated growth of the characteristic length scale
Self-consistent Quantum Kinetics of Condensate and Non-condensate via a Coupled Equations of Motion Formalism
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