A dipolar exciton fluid in a semiconductor bilayer is a wonderful system to look for the very rich quantum-collective physics that is theoretically predicted for ultracold dipolar gases [1,2]. Furthermore, these exciton fluids can be transported, controlled, and manipulated over macroscopic distances via their interactions with externally applied potentials, a property that can be utilized for new types of coherent exciton based circuitry on a chip.
Several years ago, it was predicted that the ground state of this dipolar exciton liquid is dark and that at low enough temperatures a dark Bose-Einstein condensate of dipoles should form . Another theoretical prediction suggested that at even higher densities, a transition to a classical dipolar exciton liquid should be observed . Recently we have observed interaction-induced transition from a classical to a quantum- correlated fluid and evidence for a sharp, macroscopic condensation into the dark spin states . An experimental evidence of a phase transition to a classical dipolar liquid was also very recently reported .
On the technological end, we recently demonstrated a working multi-functional, integrated exciton device. This device implements complex static as well as moving external potentials to transport, gate, and route excitonic fluxes over macroscopic distances .