Optical study of electron-electron exchange interaction in CdTe/ZnTe quantum dots

TL;DR

This study investigates electron-electron exchange interactions in CdTe/ZnTe quantum dots through photoluminescence, revealing the exchange energy, new emission lines, and magnetic field effects on singlet-triplet splitting.

Contribution

It provides the first detailed measurement of electron-electron exchange energy and identifies new emission lines related to electron singlet states in these quantum dots.

Findings

Electron singlet-triplet splitting is approximately 20.4 meV.

New emission lines associated with electron singlet configurations were observed.

Magnetic field causes a decrease in energy difference between singlet and triplet states.

Abstract

We present an experimental study of electron-electron exchange interaction in self-assembled CdTe/ZnTe quantum dots based on the photoluminescence measurements. The character and strength of this interaction are obtained by simultaneous observation of various recombination channels of a doubly negatively charged exciton, including previously unrecognized emission lines related to the electron-singlet configuration in the final state. A typical value of the electron singlet-triplet splitting, which corresponds to the exchange integral of electron-electron interaction, has been determined as 20.4 meV with a spread of 1.4 meV across the wide population of quantum dots. We also evidence an unexpected decrease of energy difference between the singlet and triplet states under a magnetic field in Faraday geometry.