Coexistence of photonic and atomic Bose-Einstein condensates in ideal atomic gases

TL;DR

This paper investigates the conditions under which photon and atomic Bose-Einstein condensates can coexist in ideal gases, predicting abrupt photon condensation and potential for light storage in cold atomic vapors.

Contribution

It provides analytical conditions for coexistence of photon and atomic BECs and predicts an abrupt photon condensation phenomenon in equilibrium with atomic condensates.

Findings

Critical temperatures and densities for BEC formation were derived.

An abrupt photon condensation can occur with slight temperature decreases.

Population inversion can be achieved by lowering temperature.

Abstract

We have studied conditions of photon Bose-Einstein condensate formation that is in thermodynamic equilibrium with ideal gas of two-level Bose atoms below the degeneracy temperature. Equations describing thermodynamic equilibrium in the system were formulated; critical temperatures and densities of photonic and atomic gas subsystems were obtained analytically. Coexistence conditions of these photonic and atomic Bose-Einstein condensates were found. There was predicted the possibility of an abrupt type of photon condensation in the presence of Bose condensate of ground-state atoms: it was shown that the slightest decrease of the temperature could cause a significant gathering of photons in the condensate. This case could be treated as a simple model of the situation known as "stopped light" in cold atomic gas. We also showed how population inversion of atomic levels can be created by lowering the temperature. The latter situation looks promising for light accumulation in atomic vapor at very low temperatures.