Light-mass Bragg cavity polaritons in planar quantum dot lattices

TL;DR

This paper theoretically explores Bragg polariton modes in quantum dot lattices within planar cavities, revealing ultra-light quasi-particles with potential for guiding and long-lived exciton-polaritons.

Contribution

It introduces the concept of Bragg polariton modes in quantum dot lattices, highlighting their unique properties such as extremely small effective mass and potential for guiding.

Findings

Polariton modes at finite momentum can be guided with long lifetimes.

Effective mass of these polaritons can be as low as 10^{-8} m_0.

Bragg polaritons are the lightest exciton-like quasiparticles in solids.

Abstract

The exciton-polariton modes of a quantum dot lattice embedded in a planar optical cavity are theoretically investigated. Umklapp terms, in which an exciton interacts with many cavity modes differing by reciprocal lattice vectors, appear in the Hamiltonian due to the periodicity of the dot lattice. We focus on Bragg polariton modes obtained by tuning the exciton and the cavity modes into resonance at high symmetry points of the Brillouin Zone. Depending on the microcavity design these polaritons modes at finite in-plane momentum can be guided and can have long lifetimes. Moreover, their effective mass can be extremely small, of the order of $10^{-8} m_0$ ($m_0$ is the bare electron mass), and they constitute the lightest exciton-like quasi-particles in solids.