Bose-Einstein condensation of photons in microcavity plasmas

TL;DR

This paper demonstrates the theoretical possibility of Bose-Einstein condensation of photons within a plasma-filled microcavity, driven by electron-induced chemical potential and thermalization via Compton scattering, with potential experimental realizations.

Contribution

It introduces a model for photon condensation in plasma microcavities, incorporating electron-induced chemical potential and Compton scattering for thermalization, supported by numerical evidence.

Findings

Evidence of photon condensation at realistic plasma densities.

Critical temperature nearly linear with photon number.

High condensate fractions at microcavity temperatures.

Abstract

Bose--Einstein condensation of a finite number of photons propagating inside a plasma-filled microcavity is investigated. The nonzero chemical potential is provided by the electrons, which induces a finite photon mass allowing condensation to occur. We derive an equation that models the evolution of the photon-mode occupancies, with Compton scattering taken into account as the mechanism of thermalization. The kinetic evolution of the photon spectrum is solved numerically, and we find evidences of condensation for realistic plasma densities, $n_e\sim 10^{14} - 10^{15}\; \text{cm}^{-3}$, compatible with microplasma technology. The critical temperature is almost linear in the number of photons, and we find high condensate fractions at microcavity-plasma temperatures, for experimentally reasonable cavity lengths ($ 100-500 \; \mu$m) and photon numbers ($10^{10}-10^{12}$).