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Microcavity polaritons - superpositions of confined photons and
excitons in quantum wells - have been the subject of much experimental
and theoretical work recently, following the experimental realisation
of condensation of polaritons. One important difference between
polariton condensates and previous examples such as Helium or cold
atoms is that polaritons have relatively short lifetimes. On the other
hand, compared to lasers, polaritons are more strongly interacting, and
therefore much better able to thermalise than are photons. This
combination leads to a picture of non-equilibrium condensation, in
which there is a continual flux of particles through the system.
After introducing a microscopic model of polaritons, and reviewing some results of this model in equilibrium [1], I will discuss how the steady states in the presence of pumping and decay can be described, considering both the nature of the steady states, and fluctuations about them[2]. Motivated by these microscopic results, I will then discuss more macroscopic features, such as the non-equilibrium spectrum, and how it affects the possibility of superfluidity away from equilibrium, and conclude by talking about the way that pumping and decay change the large-scale structure expected in a non-equilibrium condensate[3]. [1] J. Keeling, F. M. Marchetti, M. H. Szymanska, and P. B. Littlewood, Semicond. Sci. Technol. 22, R1 (2007) [2] M. H. Szymanska, J. Keeling, and P. B. Littlewood, Phys. Rev. Lett. 96, 230602 (2006). [3] J. Keeling and N. G. Berloff, Phys. Rev. Lett. 100, 250401 (2008). |
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