Imaging and Spectroscopy of an Exciton Condensate

We study the spatial and spectral properties of the photoluminescence of an exciton liquid at low temperatures and show that it evolves from a disordered liquid to a homogenous Bose-Einstein condensate, extending over a few hundred microns and covering the entire area of the mesa. The appearance of the condensate is marked by the emergence of a narrow PL peak, which gains strength as the temperature is reduced, and as the power is increased. We suggest that this peak is a result of the dark condensate formation and its interaction with the bright thermal exciton population.