Luminescence Effects in Quantum Well Structures in Magnetic and Electric Fields

We have performed experimental studies of the exciton dynamics in coupled quantum wells in electric and magnetic fields. Being composed of an electron and a hole, the excitons are Bose particles and there are theoretical predictions that they should undergo Bose-Einstein condensation (BEC). Coupled quantum wells, a two dimensional system due to the quantum confinement, are particularly suitable for studying BEC of excitons due to the ability to extend excitons' lifetime up to several microseconds. We have found that the disorder in the structure plays an important role in the properties of the exciton luminescence under magnetic field. We were also among the first to observe an unique effect---luminescence rings around the excitation spot that can span over distances of millimeters. We found that this effect is extremely dependent on the specific experimental conditions as well as some characteristic properties of the structure, like doping level, that can facilitate charge separation in two dimensions