Universality in modelling non-equilibrium pattern formation in polariton condensates

TL;DR

This paper reviews universal order parameter equations used to model non-equilibrium pattern formation in exciton-polariton condensates, highlighting their derivation from laser models and their relevance across different regimes.

Contribution

It provides a unified framework connecting various universal equations for exciton-polariton condensates derived from Maxwell-Bloch models, bridging different dynamical regimes.

Findings

Derivation of key equations from Maxwell-Bloch models

Unified treatment of equilibrium and non-equilibrium regimes

Insights into pattern formation mechanisms

Abstract

The key to understanding the universal behaviour of systems driven away from equilibrium lies in the common description obtained when particular microscopic models are reduced to order parameter equations. Universal order parameter equations written for complex matter fields are widely used to describe systems as different as Bose-Einstein condensates of ultra cold atomic gases, thermal convection, nematic liquid crystals, lasers and other nonlinear systems. Exciton-polariton condensates recently realised in semiconductor microcavities are pattern forming systems that lie somewhere between equilibrium Bose-Einstein condensates and lasers. Because of the imperfect confinement of the photon component, exciton-polaritons have a finite lifetime, and have to be continuously re-populated. As photon confinement improves, the system more closely approximates an equilibrium system. In this chapter we review a number of universal equations which describe various regimes of the dynamics of exciton-polariton condensates: the Gross-Pitaevskii equation, which models weakly interacting equilibrium condensates, the complex Ginsburg-Landau equation---the universal equation that describes the behaviour of systems in the vicinity of a symmetry--breaking instability, and the complex Swift-Hohenberg equation that in comparison with the complex Ginsburg-Landau equation contains additional nonlocal terms responsible for spacial mode selection. All these equations can be derived asymptotically from a generic laser model given by Maxwell-Bloch equations. Such an universal framework allows the unified treatment of various systems and continuously cross from one system to another. We discuss the relevance of these equations, and their consequences for pattern formation.