Microcavity polaritons in disordered exciton lattices

TL;DR

This paper studies how different types of disorder affect exciton-photon interactions in polariton systems, revealing that certain disorders can enhance coupling and that some structures are more robust, aiding future experimental designs.

Contribution

It provides a detailed analysis of disorder effects on polariton spectra in lattice-coupled exciton-photon systems, including conventional and Bragg structures, highlighting conditions that enhance or diminish coupling.

Findings

Weak disorder can increase polariton splitting.

Coupling is less sensitive to certain disorder types.

Bragg polariton features are observable with impurity-based structures.

Abstract

We investigate the interaction of excitons in a two dimensional lattice and photons in a planar cavity in the presence of disorder. The strong exciton-photon coupling is described in terms of polariton quasi-particles, which are scattered by a disorder potential. We consider three kinds of disorder: (a) inhomogeneous exciton energy, (b) inhomogeneous exciton-photon coupling and (c) deviations from an ideal lattice. These three types of disorder are characteristic of different physical systems, and their separate analysis gives insight on the competition between randomness and light-matter coupling. We consider conventional planar polariton structures (with excitons resonant to photon modes emitting normal to the cavity) and Bragg polariton structures, in which excitons in a lattice are resonant with photon modes at a finite angle satisfying the Bragg condition. We calculate the absorption spectra in the normal direction and at the Bragg angle by a direct diagonalization of the exciton-photon Hamiltonian. We found that in some cases weak disorder increases the light-matter coupling and leads to a larger polariton splitting. Moreover, we found that the coupling of excitons and photons is less sensitive to disorder of type (b) and (c). This suggests that polaritonic structures realized with impurities in a semiconductor or with atoms in optical lattices are good candidate for the observation of some of the Bragg polariton features.