Theory of polarized photoluminescence of indirect band gap excitons in type-I quantum dots

TL;DR

This paper develops a theoretical model for the polarized photoluminescence of indirect band gap excitons in type-I quantum dots, emphasizing hyperfine interactions and magnetic field effects on exciton polarization.

Contribution

It introduces a comprehensive theoretical framework for understanding exciton polarization in quantum dots with weak exchange interaction and long lifetimes, focusing on hyperfine effects and magnetic field dependence.

Findings

Polarization properties vary uniquely with magnetic field compared to conventional quantum dots.

Hyperfine interaction with Overhauser field significantly influences exciton fine structure.

The model accounts for nonradiative recombination and exchange interaction effects.

Abstract

In this work, we theoretically investigate the optical orientation and alignment of excitons in quantum dots with weak electron-hole exchange interaction and long exciton radiative lifetimes. This particular regime is realized in semiconductor heterosystems where excitons are indirect in the $\boldsymbol r$ or $\boldsymbol k$ space. The main role in the fine structure of excitonic levels in these systems is played by the hyperfine interaction of the electron in the confined exciton and fluctuations of the Overhauser field. Along with it, the effects of nonradiative recombination and exchange interaction are considered. We start with the model of vanishing exchange interaction and nonradiative exciton recombination and then include them into consideration in addition to the strong Overhauser field. In the nanoobjects under study, the polarization properties of the resonant photoluminescence are shown to vary with the external magnetic filed in completely different way as compared with the behaviour of the conventional quantum dot structures.