Coherence measurements of polaritons in thermal equilibrium reveal a power law for two-dimensional condensates
Hassan Alnatah, Qi Yao, Jonathan Beaumariage, Shouvik Mukherjee, Man Chun Tam, Z. R. Wasilewski, Ken West, Kirk Baldwin, L. N. Pfeiffer, David W. Snoke
Abstract
We have created a spatially homogeneous polariton condensate in thermal equilibrium, up to very high condensate fraction. Under these conditions, we have measured the coherence as a function of momentum and determined the total coherent fraction of this boson system from very low density up to density well above the condensation transition. These measurements reveal a consistent power law for the coherent fraction as a function of the total density over nearly three orders of its magnitude. The same power law is seen in numerical simulations solving the two-dimensional Gross-Pitaevskii equation for the equilibrium coherence.