Polariton condensates in semiconductor microcavities

Summary form only given. There has been continued interest over several decades in the possibility that excitons in semiconductors can condense into a macroscopic phase-coherent state in analogy to Bose-Einstein atomic condensates. Such phase coherence is useful-both atomic condensates and superconducting junctions have already been shown to surpass the sensitivity of existing measurements of local gravitational or magnetic fields. Although excitons are bosons, no clear signatures of the condensation have been seen, due to their strong interaction with phonons and screening charges. Confining the excitons in a semiconductor quantum well, and strongly coupling them to surrounding microcavity photons, produces exciton polaritons with new properties unlike either constituent particle. In particular, the dispersion relation of the polaritons is radically altered allowing new dynamics, and forming a trap for the polaritons. By optically exciting the system with a CW near-infra-red laser at a precise angle, a reservoir of high energy polaritons is injected. The new bosonic dynamics of the polaritons efficiently sucks them down into the polariton trap, in which a macroscopic condensate is formed.