Coherence of the exciton condensate luminescence

A new experiment to detect Bose-Einstein condensation of excitons is suggested. The experiment is a photon-counting measurement of the exciton luminescence with two detectors. As a result, the number of photons N ( t ) and the second-order coherence g (2) ( t ) emitted during the time interval t can be obtained. These quantities contain contributions from both the normal component and the condensate. It is shown in the paper that the number of photons emitted by a condensate, N (2) ( t ), can be found from the expression [ N (2) ( t )] 2 = 2[ N ( t )] 2 − g (2) ( t ). The integration of N (2) ( t ) over the spectrum gives the value of the order parameter.