arXiv subjects

Suzanne Dang

Publications and source records attributed to Suzanne Dang.

4 recordsLinked to original sources

arXiv2018

Temporal Coherence of Spatially Indirect Excitons across Bose-Einstein Condensation: the Role of Free Carriers

We study the time coherence of the photoluminescence radiated by spatially indirect excitons confined in a 10 $μ$m electrostatic trap. Above a critical temperature of 1 Kelvin, we show that the photoluminescence has a homogeneous spectral width of about 500 $μ$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 $μ$eV.

cond-mat.quant-gas↗

arXiv2018

Defect-Driven Superfluid Crossover for Two-Dimensional Dipolar Excitons Trapped at Thermodynamic Equilibrium

We study ultra-cold dipolar excitons confined in a 10$μ$m trap of a double GaAs quantum well. Based on the local density approximation, we unveil for the first time the equation of state of excitons at pure thermodynamic equilibrium. In this regime we show that, below a critical temperature of about $1$ Kelvin, a superfluid forms in the inner region of the trap at a local exciton density $n \sim 2-3 \, 10^{10} \text{cm}^{-2}$, encircled by a more dilute and normal component in the outer rim of the trap. Remarkably, this spatial arrangement correlates directly with the concentration of defects in the exciton density which exhibits a sudden decrease at the onset of superfluidity, thus pointing towards an underlying Berezinskii-Kosterlitz-Thouless mechanism.

cond-mat.quant-gas↗

arXiv2017

Dynamical control over the confinement of spatially indirect excitons in electrostatic traps of GaAs coupled quantum wells

We study spatially indirect excitons confined in a 10 $μ$m wide electrostatic trap of a GaAs double quantum well. We introduce a technique to control the amplitude of the electric field interacting with the excitons electric dipole, with nanosecond precision. Our approach relies on electronic waveforms corrected for the distorsions occurring at highest frequencies so that impedance matching is not necessary. Thus, we manipulate the confinement of cold gases without inducing sizeable perturbations down to sub-Kelvin bath temperatures.

cond-mat.mes-hall↗

arXiv2017

Quantized Vortices and Four-Component Superfluidity of Semiconductor Excitons

We study spatially indirect excitons of GaAs quantum wells, confined in a 10 microns electrostatic trap. Below a critical temperature of about 1 Kelvin, we detect macroscopic spatial coherence and quantised vortices in the weak photoluminescence emitted from the trap. These quantum signatures are restricted to a narrow range of density, in a dilute regime. They manifest the formation of a four-component superfluid, made by a low population of optically bright excitons coherently coupled to a dominant fraction of optically dark excitons.

cond-mat.quant-gas↗