Science:
We have created polaritons in a harmonic potential trap
analogous to atoms in optical traps. The trap can be loaded by
creating polaritons 50 micrometers from its center that are
allowed to drift into the trap. When the density of polaritons
exceeds a critical threshold, we observe a number of signatures
of Bose-Einstein condensation: spectral and spatial narrowing,
a peak at zero momentum in the momentum distribution,
first-order coherence, and spontaneous linear polarization of
the light emission. The polaritons, which are eigenstates of
the light-matter system in a microcavity, remain in the strong
coupling regime while going through this dynamical phase
transition.
