Random fine structure and polarized luminescence of triplet excitons in semiconductor nanocrystals

TL;DR

This paper develops a theoretical model for polarized photoluminescence in semiconductor nanocrystals, accounting for random fine structure effects from exchange and hyperfine interactions.

Contribution

It introduces a statistical approach using random matrix theory to describe the effects of fine structure on exciton luminescence and polarization properties.

Findings

Luminescence intensity depends on fine structure splitting and exciton lifetime.

External magnetic fields can suppress optical alignment and enhance optical orientation.

The model explains polarization behavior in nanocrystal ensembles with random interactions.

Abstract

We present a theory of polarized photoluminescence of triplet excitons in semiconductor nanocrystal ensembles with the random fine structure contributed by the electron-hole exchange and carrier-nuclear hyperfine interactions. The interaction parameters are assumed to be normally and isotropically distributed. In particular, the exchange interaction is described by the Gaussian orthogonal ensemble of random matrices. The intensity of luminescence as well as the optical orientation and alignment are calculated as functions of the fine structure splitting parameters and the exciton lifetime. We have also analyzed the suppression of optical alignment and enhancement of optical orientation in an external longitudinal magnetic field.