Exciton dephasing in quantum dots: Coupling to LO phonons via excited states

TL;DR

This paper reveals a new mechanism for spectral broadening and dephasing in quantum dots caused by coupling to LO phonons, which becomes evident when considering the full exciton level manifold, including wetting-layer states.

Contribution

It introduces a theoretical model demonstrating exciton dephasing via LO phonons involving multiple excitonic states, including continuum levels, which was not previously considered.

Findings

Dephasing arises from coupling to LO phonons when all excitonic states are included.

The quadratic coupling model is generalized to multiple excitonic states.

Spectral broadening is demonstrated in various quantum dot types.

Abstract

We have found a novel mechanism of spectral broadening and dephasing in quantum dots (QDs) due to the coupling to longitudinal-optical (LO) phonons. In theory, this mechanism comes into play only if the complete manifold of exciton levels (including those in the wetting-layer continuum) is taken into account. We demonstrate this nontrivial dephasing in different types of QDs, using the exactly solvable quadratic coupling model, here generalized to an arbitrary number of excitonic states.