Thermodynamics of Trapped Photon Gases at Dimensional Crossover from 2D to 1D

TL;DR

This paper analytically investigates the thermodynamics of a harmonically confined ideal photon Bose gas undergoing a dimensional crossover from 2D to 1D, highlighting how confinement anisotropy influences thermodynamic properties.

Contribution

It provides a detailed analytical study of the thermodynamics during the 2D to 1D crossover in a confined photon Bose gas, relevant for experimental microcavity setups.

Findings

Thermodynamic quantities reveal dimensional information during crossover.

Analytical expressions for finite photon numbers in confined geometries.

Identification of conditions for effective 1D behavior in photon gases.

Abstract

Photon Bose-Einstein condensates are characterised by a quite weak interaction, so they behave nearly as an ideal Bose gas. Moreover, since the current experiments are conducted in a microcavity, the longitudinal motion is frozen out and the photon gas represents effectively a two-dimensional trapped gas of massive bosons. In this paper we focus on a harmonically confined ideal Bose gas in two dimensions, where the anisotropy of the confinement allows for a dimensional crossover. If the confinement in one direction is strong enough so that this squeezed direction is frozen out, then only one degree of freedom survives and the system can be considered to be quasi-one dimensional. In view of an experimental set-up we work out analytically the thermodynamic properties for such a system with a finite number of photons. In particular, we focus on examining the dimensional information which is contained in the respective thermodynamic quantities.