Interplay between multipole expansion of exchange interaction and Coulomb correlation of exciton in colloidal II-VI quantum dots

TL;DR

This study investigates how Coulomb correlation affects the emission properties of excitons in colloidal II-VI quantum dots, revealing different dominant interactions in zincblende and wurtzite structures.

Contribution

It introduces a theoretical model that explains the impact of Coulomb correlation on exciton properties and compares it with experimental data for different quantum dot structures.

Findings

Coulomb correlation significantly influences exciton energy and emission in ZnO dots.

Multipole expansion dominates exciton fine structure in CdSe/ZnS dots.

Excellent agreement between model predictions and experimental measurements.

Abstract

We study the effect of Coulomb correlation on the emission properties of the ground state exciton in zincblende CdSe/ZnS core-shell and in wurtzite ZnO quantum dots. We validate our theory model by comparing results of computed exciton energies of CdSe/ZnS quantum dots to photoluminescence and scanning near-field optical microscopy measurements. We use that to estimate the diameter of the quantum dots using a simple model based on infinitely deep quantum well and compare the results with the statistics of the atomic force microscopy scans of CdSe/ZnS dots, obtaining excellent agreement. Thereafter, we compute the energy fine structure of exciton, finding striking difference between properties of zincblende CdSe/ZnS and wurtzite ZnO dots. While in the former the fine structure is dominated by the dipole terms of the multipole expansion of the exchange interaction, in the latter system that is mostly influenced by Coulomb correlation. Furthermore, the correlation sizeably influences also the exciton binding energy and emission radiative rate in~ZnO dots.