Calculation of pure dephasing for excitons in quantum dots

TL;DR

This paper models pure dephasing of excitons in quantum dots caused by phonons, revealing how dephasing times depend on dot size and phonon interactions, with implications for quantum information processing.

Contribution

It provides a detailed calculation of exciton dephasing times considering phonon interactions, highlighting size dependence and the difference between LO and acoustic phonon effects.

Findings

Dephasing is partial at zero temperature, with polarization decaying to a finite value.

Dephasing from LO phonons occurs on a longer timescale than acoustic phonons.

Dephasing times vary significantly with quantum dot size.

Abstract

Pure dephasing of an exciton in a small quantum dot by optical and acoustic phonons is calculated using the ``independent boson model''. Considering the case of zero temperature the dephasing is shown to be only partial which manifests itself in the polarization decaying to a finite value. Typical dephasing times can be assigned even though the spectra exhibits strongly non-Lorentzian line shapes. We show that the dephasing from LO phonon scattering, occurs on a much larger time scale than that of dephasing due to acoustic phonons which for low temperatures are also a more efficient dephasing mechanism. The typical dephasing time is shown to strongly depend on the quantum dot size whereas the electron phonon ``coupling strength'' and external electric fields tend mostly to effect the residual coherence. The relevance of the dephasing times for current quantum information processing implementation schemes in quantum dots is discussed.