Evidence of Bose-Einstein condensation of excitons in semimetallic AlxGa1-xSb/InAs quantum wells

We have directly observed the Bose-Einstein Condensation (BEC) in the trans port properties of excitons moving on a heterointerface of type II AlxGa1-x Sb/InAs quantum wells. The unavoidable alloy potential fluctuations lead to localized states on the interfaces which are critically important for the observation of the BEC in exactly two dimensions. By changing the alloy com position and the quantum well width, the depth of the potential fluctuation s can be varied, and the measured BEC behavior is consistent with the theor etical prediction. Our results constitute a first confirmation of the exist ence of BEC for a non-interacting system in two dimensions.