Dynamic polariton condensation in a single GaN nanowire-dielectric microcavity

We have experimentally investigated the dynamic polariton condensation behavior in a single GaN nanowire strongly coupled to a dielectric microcavity under nonresonant optical excitation. Both time-integrated and time-resolved polariton luminescence measurements have been made in the temperature range of 25 to 100 K (corresponding to exciton-cavity photon detuning of -3.0 to +4.2 meV). Polariton lasing is observed in the entire temperature range, with the lowest threshold energy of 57 nJ/cm² measured at 50 K (δ = -1.3 meV). All the measurements indicate that at the lower temperatures the degenerate polariton condensate is not in thermal equilibrium with the phonon bath. At 85 and 100 K (δ = +2.3 and 4.2 meV), the system attains a state close to thermal equilibrium via dynamic Bose condensation. The best results are obtained at T_latt = 85 K, for which T_LP = 88.8 K, and this is the highest temperature recorded for an equilibrium phase transition in exciton-polariton condensates.