Optically induced energy and spin transfer in non-resonantly coupled pairs of self-assembled CdTe/ZnTe quantum dots

TL;DR

This study investigates energy and spin transfer in coupled CdTe/ZnTe quantum dots, revealing high spin transfer efficiency and a coherent polarization conversion mechanism, advancing understanding of quantum dot interactions.

Contribution

It demonstrates non-resonant energy and spin transfer in asymmetrically coupled quantum dots with high efficiency and identifies a coherent polarization conversion process.

Findings

Spin transfer efficiency of 70% with magnetic field, 40% without.

Identification of a coherent linear-to-circular polarization conversion at 43%.

Observation of energy and spin transfer dynamics in coupled quantum dots.

Abstract

Asymmetrical horizontal interdot coupling was demonstrated to exist in a system of a single plane of self-assembled CdTe/ZnTe quantum dots. Photoluminescence excitation (PLE), second order photon correlation and optical orientation were used as main experimental tools. Each individual absorbing dot was identified by a sharp PLE resonance, assigned to neutral exciton transition, while the corresponding emission contained several excitonic transitions of different charge states in another single quantum dot different from the absorbing one. Energy and spin transfer dynamics were studied. A high efficiency of spin transfer was found from optical orientation in a vertical magnetic field (70%) as well as without the magnetic field (40%), in spite of a significant anisotropic exchange splitting of the absorbing dot. Coherent mechanism of linear-to-circular polarization conversion was identified, with an efficiency (43%) close to the theoretical limit of 50%.