  We experimentally investigate the lateral diffusion of dipolar excitons in
coupled quantum wells in two (2D) and one (1D) dimensions. In 2D, the exciton
expansion obeys non-linear temporal dynamics due to the repulsive dipole
pressure at a high exciton density, in accordance with recent reports. In
contrast, the observed 1D expansion behaves linearly in time even at high
exciton densities. The corresponding 1D diffusion coefficient exceeds the one
in 2D by far and depends linearly on the exciton density. We attribute the
findings to screening of quantum well disorder by the dipolar excitons.

Mesoscale and Nanoscale Physics