Bose-Einstein Condensation of Dark-State Polaritons

We propose and theoretically analyse a mechanism for Bose-Einstein condensation of stationary dark-state polaritons (DSP) [1]. DSP's are quasi-particle arizing in the Raman interaction of light with three-level $\Lambda$-type systems. They are the basis of such phenomena as ultra-slow and stationary light. In contrast to exciton-polaritons, for which condensation has recently been observed [2], they have a long intrinsic lifetime, can be created with a three-dimensional quadratic dispersion profile, thus alleviating the need of resonators, and have a dynamically variable effective mass. Due to the very small effective mass the condensation temperature can be several orders of magnitude larger than that of atomic vapors. We introduce stationary dark-state polaritons, propose methods for their incoherent generation, and analyze their thermalization. Finally potential methods for an experimental verification of condensation will be discussed. \begin{description} \item{[1]} M. Fleischhauer and M.D. Lukin, PRL {\bf 84}, 5094 (2000); \\ F. Zimmer {\it et al.} arXiv:0712.0060 \item{[2]} J. Kasprzak {\it et al.} Nature {\bf 443}, 409 (2006) \end{description}