Polariton Condensation in a One-Dimensional Disordered Potential

We study the coherence and density modulation of a nonequilibrium exciton-polariton condensate in a one-dimensional valley with disorder. By means of interferometric measurements we evidence a modulation of the first-order coherence function and we relate it to a disorder-induced modulation of the condensate density, that increases as the pump power is increased. The nonmonotonic spatial coherence function is found to be the result of the strong nonequilibrium character of the one-dimensional system, in the presence of disorder.

Figure 1

Michelson interferometer in the mirror-retroreflector configuration: (a) the mirror arm is superposed to (b) the retroreflector arm, which is a centrosymmetric replica of it, in order to get the (c) interferogram.

Figure 2

(a) Real-space PL coming from a specific 1D disorder valley and (b) associated interference pattern (both taken above condensation threshold). The corresponding real-space energy spectrum are shown in (c) and (d) respectively, where the a single-energy 1D state can be observed. The polariton dispersion, below condensation threshold, is shown in (e) along $k_x$ (along the linear condensate) and in (f) along $k_y$ (1D confinement direction). Note: the color scale of (b),(c) and (d) is saturated to make the signal modulation more visible.

Figure 3

(a) Real-space normalized polariton density profiles along the 1D condensate, for different values of the excitation power. The black dotted curve is the reference profile considered in the analysis of the disorder-induced density modulations. (b) Standard deviation of the measured density profiles with respect to the Gaussian reference profile (background color gradient identifies three different regimes, as explained in the text).

Figure 4

First-order spatial coherence function along the linear condensate for different values of the pump power. The error bars quantify the uncertainty in the numerical determination of the $g^{(1)}$ value.