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We study the time coherence of the photoluminescence radiated by spatially indirect excitons confined in a 10 $mu$m electrostatic trap. Above a critical temperature of 1 Kelvin, we show that the photoluminescence has a homogeneous spectral width of about 500 $mu$eV which weakly varies with the exciton density. By contrast, the spectral width reduces by two-fold below the critical temperature and for experimental parameters at which excitons undergo a gray Bose-Einstein condensation. In this regime, we find evidence showing that the excitons temporal coherence is limited by their interaction with a low-concentration of residual excess charges, leading to a minimum photoluminescence spectral width of around 300 $mu$eV.
We study semiconductor excitons confined in an electrostatic trap of a GaAs bilayer heterostructure. We evidence that optically bright excitonic states are strongly depleted while cooling to sub-Kelvin temperatures. In return, the other accessible an
We present theoretical studies of condensation of indirect excitons in a trap. Our model quantifies the effect of screening of the trap potential by indirect excitons on exciton condensation. The theoretical studies are applied to a system of indirec
We present an alternative method for determining the sound velocity in atomic Bose-Einstein condensates, based on thermodynamic global variables. The total number of trapped atoms was as a function of temperature carefully studied across the phase tr
We report on the attainment of Bose-Einstein condensation with ultracold strontium atoms. We use the 84Sr isotope, which has a low natural abundance but offers excellent scattering properties for evaporative cooling. Accumulation in a metastable stat
We report on the attainment of Bose-Einstein condensation of 86Sr. This isotope has a scattering length of about +800 a0 and thus suffers from fast three-body losses. To avoid detrimental atom loss, evaporative cooling is performed at low densities a