Condensation in Periodic Potential

In these experiments we show the influence of the tunable potential introduced by a surface acoustic wave (SAW) on the polariton system. In angularly resolved photoluminiscence(PL) experiments we show that the effect of a SAW is to create a lateral polaritonic superlattice which folds the polariton dispersion in to mini-Brillouin zones (MBZ) with the size of the SAW wavelength. This resultsin the formation of energetic bandgaps due to anticrossing of the folded levels at the boundaries of the MBZ. We show that they can be tuned in a simple manner by increasing the applied acoustic power.

Also in this work we demonstrate that the tunable potential introduced by a surface acoustic wave (SAW) on a homogeneous polariton condensate leads to fragmentation of the condensate into an array of wires which move with the acoustic velocity. Reduction of the spatial coherence of the condensate emission along the surface acoustic wave direction is attributed to the suppression of coupling between the spatially modulated condensates. Interparticle interactions observed at high polariton densities screen the acoustic potential, partially reversing its effect on spatial coherence, see figure below.

Folding of the polariton dispersion (right) as a result of periodic potential introduced by the surface acoustic wave compared to the unperturbed case (left)

Folding of the polariton dispersion (right) as a result of periodic potential introduced by the surface acoustic wave compared to the unperturbed case (left)

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