Dipolar exciton hydrodynamics, controlled interactions and multi-functional integration: towards an exciton-based opto-electronic multiplexer

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A dipolar (or indirect) exciton (Ix) in semiconductor nanostructures is an exciton consisting of an electron and a holes confined in two closely spaced quantum wells (QWs). The charge separation, which is normally formed by applying an electric field across the double QW structure, enhances the Ix: radiative lifetime (up to the ms-range) while still maintaining the electron-hole Coulomb interaction. The long lifetimes allow for the storage of a large density of cold excitons, as well as for their transport and manipulation in the ns time scale. In addition, their dipolar nature induces a strong exciton-exciton interactions. Finally, Ixs are composite bosons and, therefore, susceptible to collective bosonic effects like superfluidity and Bose-Einstein condensation.This proposal aims at the investigation of the interplay between interactions and collective behavior of Ixs in laterally confined potentials with mesoscopic ( ~1 µm) dimensions. Confinement will be used to control the Ix density: it will be provided by laterally structured gates as well as by moving acoustic fields created by acoustic waves. The latter will also be used to transport IxS as well as to investigate their hydrodynamic properties under motion. Exciton-exciton interaction will be exploit for the realization of exciton control gates. The results of the studies will be applied to demonstrate an exciton-based opto-electronic multiplexer capable of coupling exciton fluids separated by several hundreds of µm.