Dynamics of a Mn spin coupled to a single hole confined in a quantum dot

TL;DR

This paper investigates the dynamics of a Mn spin coupled to a confined hole in a quantum dot, demonstrating efficient optical initialization and analyzing relaxation mechanisms influenced by valence band mixing.

Contribution

It provides a detailed experimental and theoretical analysis of the optical pumping and relaxation dynamics of a Mn-hole spin system in quantum dots, highlighting the role of electron-Mn flip-flops.

Findings

Efficient optical initialization of Mn-hole spin within tens of nanoseconds.

Measured hole-Mn spin relaxation times in the microsecond range.

Valence band mixing induces spin relaxation in the quantum dot system.

Abstract

Using the emission of the positively charged exciton as a probe, we analyze the dynamics of the optical pumping and the dynamics of the relaxation of a Mn spin exchange-coupled with a confined hole spin in a II-VI semiconductor quantum dot. The hole-Mn spin can be efficiently initialized in a few tens of $ns$ under optical injection of spin polarized carriers. We show that this optical pumping process and its dynamics are controlled by electron-Mn flip-flops within the positively charged exciton-Mn complex. The pumping mechanism and its magnetic field dependence are theoretically described by a model including the dynamics of the electron-Mn complex in the excited state and the dynamics of the hole-Mn complex in the ground state of the positively charged quantum dot. We measure at zero magnetic field a spin relaxation time of the hole-Mn spin in the $\mu s$ range or shorter. This hole-Mn spin relaxation is induced by the presence of valence band mixing in self-assembled quantum dots.