Coherence and Optical Emission from Bilayer Exciton Condensates

Figure 2

General structure of the phase diagram of an electron-hole system. FE: free excitons; EHP: electron-hole plasma; BEC: Bose-Einstein condensate of excitons; EI: exciton insulator state, which is a BCS-like state with a Fermi level for the electrons and for the holes. The transition from BEC to BCS may be gradual. At high pair density 𝑛, decreasing the temperature gives one critical 𝑇_𝑐 in which both pairing and condensation occur, in the EI (BCS-like) state. At lower density, there can be two critical temperatures: one for pairing and a second for condensation.