Optical spectra of quantum dots: effects of non-adiabaticity

TL;DR

This paper develops a non-adiabatic theory for phonon-assisted optical transitions in semiconductor quantum dots, explaining high phonon satellite intensities and discrepancies in multi-phonon spectra that the adiabatic approximation cannot account for.

Contribution

It introduces a non-adiabatic theoretical framework for quantum dot optical spectra, surpassing the limitations of the adiabatic approximation.

Findings

Non-adiabatic effects cause mixing of exciton and phonon states.

High intensities of phonon satellites are explained by non-adiabaticity.

Discrepancies in multi-phonon spectra are resolved with the new theory.

Abstract

It is shown that in many cases an adequate description of optical spectra of semiconductor quantum dots requires a treatment beyond the commonly used adiabatic approximation. We have developed a theory of phonon-assisted optical transitions in semiconductor quantum dots, which takes into account non-adiabaticity of the exciton-phonon system. Effects of non-adiabaticity lead to a mixing of different exciton and phonon states that provides a key to the understanding of surprisingly high intensities of phonon satellites observed in photoluminescence spectra of quantum dots. A breakdown of the adiabatic approximation gives an explanation also for discrepancies between the serial law, observed in multi-phonon optical spectra of some quantum dots, and the Franck-Condon progression, prescribed by the adiabatic approach.