Résumé
Indirect excitons (IXs) offer an opportunity to explore dipolar bosonic fluids in semiconductors. Indeed, IXs are quasiparticles hosted by quantum heterostructures, e.g. quantum wells (QWs). Such IXs are Coulomb-bound pairs consisting of an electron and a hole individually confined at the two opposite QW interfaces. Main properties of IX fluids, such as radiative lifetimes, in-plane transport, achievable densities, interactions and possible collective behaviour are determined by IX dipole length, roughly given by the QW width, d. In contrast with GaAs-based heterostructures, GaN/(AlGa)N QWs may host IXs with relatively high binding energy even in the absence of external electric field [1]. Independent control over the IX density and temperature in electrostatic traps, consisting ofvarious metallic patterns on the sample surface, has been demonstrated [2].In this presentation we explore the effect of the dipole length on spatio-temporal dynamics of IX fluids, either confined in electrostatic traps, or expanding freely in the GaN/AlGaN QW plane, see Fig. 1. Relative importance of IX lifetime, IX-IX interaction strength and interface roughness in the quest for (i) efficient IX transport and (ii) realisation of high-density cold IX fluids is addressed. The analysis is supported by the drift-diffusion-losses model accounting for dipole length dependent interactions between IXs. The obtained results contribute to the understanding of IX fluid properties in GaN/AlGaN QWs, and could help optimisation and control of their collective behaviour.[1] F. Fedichkin et al., Phys. Rev. Applied 6, 014011 (2016)[2] F. Chiaruttini et al., Nano Letters 19, 4911 (2019)