Sensitive linear response of an electron-hole superfluid in a periodic potential

Abstract

We consider excitons in a two-dimensional periodic potential and study the linear response of the excitonic superfluid to an electromagnetic wave at low and high densities. It turns out that the static structure factor for small wavevectors is very sensitive to a change of density and temperature. It is a consequence of the fact that thermal fluctuations play a crucial role at small wavevectors, since exchanging the order of the two limits, zero temperature and vanishing wavevector, leads to different results for the structure factor. This effect could be used for high accuracy measurements in the superfluid exciton phase, which might be realized by a gated electron-hole gas. The transition of the exciton system from the superfluid state to a non-superfluid state and its manifestation by light scattering are discussed.

Electron-hole superfluidity controlled by a periodic potential

“…This would open a wide avenue for measurements of quantum effects near the EHP-superfluid transition as well as inside the EHP and the superfluid through quantum excitations. A first step in this direction was the calculation of the density-density correlation and the structure factor, which indicates a characteristic increase near the transition [69]. Another possibility is to determine quantum transport properties in the EHP and the superfluid.…”