Exciton–Polariton Coupling with Acoustic Phonons

Abstract

Exciton–polariton are solid-state composite bosons with a high photonic character and low effective mass, which have been proven to undergo a thermodynamic phase transition to a macroscopically occupied state—a condensate—above a characteristic threshold density (Kasprzak et al. Nature 443:409, 2006; Balili et al. Science 316:1007, 2007). Full exploitation of the unique polariton properties requires dynamic processes for the dynamic confinement and control of the interaction between condensates. Here, we demonstrate a novel approach for the formation of arrays of interacting polariton condensates based on the spatial and temporal modulation by a coherent acoustic phonon. Analogous to the confinement of atomic Bose–Einstein condensates by optical lattices, the acoustic spatial modulation forms an array of polariton wires aligned with the phonon wavefronts. We show that the moving acoustic modulation controls both the energetic configuration and the spatial coherence length of the polariton condensates. Furthermore, the confinement potential moves with the acoustic velocity, thereby transporting the polariton wires. These moving acoustic confinement potentials provide, therefore, a powerful framework for manipulation and transport of solid-state condensates.