Spatial distribution of cold indirect excitaons in lateral Stark traps

Full text: Coupled quantum wells (CQWs) under applied electric fields are a popular system for trapping cold excitons to investigate collective quantum properties. Due to the small spatial overlap of the electron and hole wavefunctions, the indirect excitons in this system have a long radiative lifetime in addition to repulsive interactions due to the dipole alignment. In analogy to the use of magnetic traps for neutral atoms, we present a technique of applying localized Stark shifts in the CQW using transparent electrical contacts to create a lateral potential. The numerical and experimental profiles of a range of these traps are investigated. These potential traps can be created with nearly arbitrary profiles offering distinct advantages over other trapping schemes. Using these traps, we experimentally and theoretically investigate the possibility of observing a phase transition to a Bose-Einstein condensate of excitons by measurement of the spatial profile and momentum distribution. Within a mean-field approach using the equation of motion technique for the Green's functions we determine the order parameter and a phase diagram detailing physical observables in this system using exact numerical potentials. This trapping scheme allows for complicated space and time dependent potentials and a possible pathway to circuits utilizing excitonic degrees of freedom. The consequences of using these structures to create analogs of optical lattices and Josephson junctions for excitons are also investigated. (author)