BEC-BCS crossover in a system of microcavity polaritons

Jonathan Keeling MIT

Recently, microcavity polaritons have been studied as a possible
candidate for observation of Bose Condensation of quasiparticles in
solid state systems.

Such systems consist of planar microcavities containing quantum
wells, in which the quantum-well excitons are strongly coupled to the
confined photon modes, leading to new quasi-particles: microcavity
polaritons. Because of the photonic component, these particles
have a low effective mass, which suggests that condensation may be
possible at elevated temperatures.

After introducing these systems, and providing a brief review of the
results of experiments looking for condensation, I will explain how
including internal structure of polaritons modifies the phase
boundary. While at low densities the transition temperature is
controlled by the effective mass; at higher, yet experimentally
accessible densities, the phase transition becomes more
mean-field-like, and the critical temperature is instead given by a
BCS-like form.

Keeling et al. Phys. Rev. Lett. 93 226403 (2004)
Keeling et al. Phys. Rev. B. 72 115320 (2005)