Exciton-polariton condensation in a natural two-dimensional trap

Bose-Einstein condensation of exciton polaritons has recently been reported in homogeneous structures only affected by random in-plane fluctuations. We have taken advantage of the ubiquitous defects in semiconductor microcavities to reveal the spontaneous dynamical condensation of polaritons in the quantized levels of a trap. We observe condensation in several quantized states, taking their snapshots in real and reciprocal space. We also show the effect of particle interactions for high occupation numbers, revealed by a change in the confined wave function toward the Thomas-Fermi profile.