Spatial spreading of the condensate of magnetoexcitons in a quantum Hall insulator

The spatial spreading of a dense ensemble of spin cyclotron magnetoexcitons in a quantum Hall insulator at the filling factor $\nu= 2$ is visualized using an optical system with a high aperture ratio. It is found that nondiffusive propagation over macroscopic distances is characteristic not only of excitons with a momentum on the order of the reciprocal magnetic length, which form a coherent condensate of magnetoexcitons, but also of excitons with very low momenta. The nondiffusive propagation of magnetoexciton condensates in real space is accompanied by a huge threshold increase in the amplitude of light reflection from excitations. The possible explanations of the observed behavior are discussed.