Coherence measurements of polaritons in thermal equilibrium reveal a power law for two-dimensional condensates.

Alnatah, Hassan; Yao, Qi; Beaumariage, Jonathan; Mukherjee, Shouvik; Tam, Man Chun; Wasilewski, Zbigniew; West, Ken; Baldwin, Kirk et al. · Sci Adv · 2024

basic_science · Level V

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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.