Bose-Einstein Condensation (BEC) is a process which occurs at low temperature when an ensemble of bosons cools down and enters a single quantum state. In most of the experiments, this condensation process includes the atomic gases. But in solid-state systems, which has a long history of generating new types of particles and quasiparticles, BEC can occur in quasiparticles e.g. fermion-like excitations of Bose- condensed Cooper pairs in a superconductor.
One class of such quasiparticles is polaritons, which form from electronic excitations coupled to photons in a microcavity. Polaritons are not fundamentally different in character from elementary particles; they are just highly renormalized to have different properties. In particular, polaritons can be viewed as photons having an effective mass and much stronger interactions than photons in a vacuum.
“A carefully engineered coupling between light and matter could pave the way to a room-temperature Bose–Einstein condensate.”
In this work supported by the NSF and the Engineering and Physical Sciences Research Council, David Snoke and Peter Littlewood have shown the trapping and coupling of polariton with photon in microcavities. Authors have shown a typical structure for polariton experiments where polariton effect will occur with just one quantum well. If a quantum well is placed at an antinode of the confined photon mode in an optical cavity, and if the energy of the exciton is close to that of a photon in the cavity, then the exciton and photon states couple to each other. The standard effect of quantum mechanical mixing leads to two new eigenstates, each of which is a linear combination of the photon and exciton states. Those new eigenstates are the polaritons.