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When the average inter-particle distance is larger than the exciton Bohr diameter, excitons form a dilute Bose gas and are expected to undergo Bose-Einstein condensation (BEC) at standard cryogenic temperatures. Indirect excitons (IX) in coupled quantum wells are particularly exciting prospects in this regard due to their long lifetime, which enables establishing quasi-equilibrium. Here we study the formation dynamics of a dark IX condensate in a GaAs/Al0.28GaAs system at low temperatures, spreading over hundreds of microns. We find that the condensate density is determined by spin flipping collisions among the condensate excitons and between them and the thermal bath. We construct a rate equations model that accounts for these interactions and quantitatively reproduces the system's behavior. Our imaging measurements of the PL intensity reveal that the condensate gradually evolves from a fragmented Bose glass phase to a smooth and delocalized condensate as a function of reducing bath temperature. Resonant Rayleigh scattering measurements show that the static disorder in the sample is effectively screened in the presence of the condensate, consistent with this picture. Finally, in a system where the phase transition occurs abruptly at relatively high excitation powers, we find that the condensate exhibits a set of properties of a high-density liquid. We determine the phase diagram of this gas-liquid transition in the density-temperature plane. We find that the latent heat of the transition exhibits a linear dependence on the temperature below 1 K, as expected for a transition to BEC. This behavior serves as evidence for a quantum liquid-like behavior of the long-lived IXs in the system at low temperatures. |