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

TL;DR

This paper investigates how the linear response of an excitonic superfluid in a 2D periodic potential varies with density and temperature, highlighting its potential for precise measurements and phase transition detection.

Contribution

It reveals the sensitivity of the static structure factor to density and temperature changes, emphasizing the role of thermal fluctuations in excitonic superfluids.

Findings

Structure factor highly sensitive to density and temperature.

Thermal fluctuations significantly influence small wavevector responses.

Potential for high-precision measurements in superfluid exciton phases.

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.