SPIN DEGREE-OF-FREEDOM IN 2-DIMENSIONAL EXCITON CONDENSATES

We present a theoretical analysis of a spin-dependent multicomponent c ondensate in two dimensions. The case of a condensate of resonantly ph otoexcited excitons having two different spin orientations is studied in detail. The energy and the chemical potentials of this system depen d strongly on the spin polarization. When electrons and holes are loca ted in two different planes, the condensate can be either totally spin polarized or spin unpolarized, a property that is measurable. The pha se diagram in terms of the total density and electron-hole separation is discussed.