Estimating the conditions for polariton condensation in organic thin-film microcavities

TL;DR

This paper investigates the conditions under which Bose condensation of polaritons can occur in organic microcavities, highlighting the roles of interactions, cavity geometry, and biexciton binding energy in the condensation process.

Contribution

It introduces a model Hamiltonian for organic polaritons and analyzes how interactions and system parameters influence Bose condensation and ground state properties.

Findings

Ideal 2D Bose gas does not condense without interactions.

Interacting polariton gas can undergo Bose condensation depending on parameters.

Strongly bound biexcitons lead to localized soliton states instead of condensation.

Abstract

We examine the possibility of observing Bose condensation of a confined two-dimensional polariton gas in an organic quantum well. We deduce a suitable parameterization of a model Hamiltonian based upon the cavity geometry, the biexciton binding energy, and similar spectroscopic and structural data. By converting the sum-over-states to a semiclassical integration over $d$-dimensional phase space, we show that while an ideal 2-D Bose gas will not undergo condensation, an interacting gas with the Bogoliubov dispersion $H(p)\approx s p$ close to $p=0$ will undergo Bose condensation at a given critical density and temperature. We show that $T_c/\sqrt{\rho_c}$ is sensitive to both the cavity geometry and to the biexciton binding energy. In particular, for strongly bound biexcitons, the non-linear interaction term appearing in the Gross-Pitaevskii equation becomes negative and the resulting ground state will be a localized soliton state rather than a delocalized Bose condensate.