Comment on: "Luminescence spectra of quantum dots in microcavities."

TL;DR

This comment clarifies the relationship between energy exchange coherence and emission spectra in quantum dot microcavities, establishing that strong coupling correlates with oscillating population dynamics.

Contribution

It demonstrates a direct link between strong coupling conditions and spectral features in quantum dot microcavity models, applicable to both bosonic and fermionic matter.

Findings

Strong coupling implies oscillating population dynamics.

Eigenvalues with non-zero imaginary parts indicate strong coupling.

Conditions are valid for both bosonic and fermionic matter.

Abstract

In this comment we show that there is a direct connection between coherent exchange of energy among light and matter and the emission spectrum of a microcavity quantum dot system as modeled in Phys. Rev. B 79, 235325 (2009) [arXiv:0807.3194] by F. P. Laussy, E. del Valle, and C. Tejedor. To do so, we show that in their model the necessary and sufficient conditions for having eigenvalues with non-zero imaginary parts in the propagator of the bare mode populations, are the same as for having strong coupling in the emission spectrum. This amounts to saying that, whenever there is strong coupling there will be oscillating frequencies in the dynamics of the populations. These conditions are valid both for the case where matter is treated as bosonic or fermionic, in the spontaneous emission case.