Spin dynamics of Mn impurities and their bound acceptors in GaAs

TL;DR

This study uses spin-dynamics simulations to explore how Mn impurities interact magnetically in GaAs, revealing the roles of spin-orbit coupling, exchange interactions, and impurity separation in their dynamic behavior.

Contribution

It introduces a mixed quantum-classical spin-dynamics approach to analyze the time evolution of Mn impurity spins and their interactions in GaAs, including single and paired impurities.

Findings

Identified characteristic frequencies linked to spin-orbit and exchange interactions.

Detected signatures of carrier-mediated exchange in impurity spin dynamics.

Showed how impurity separation and initial spin configuration affect temporal correlations.

Abstract

We present results of tight-binding spin-dynamics simulations of individual and pairs of substitutional Mn impurities in GaAs. Our approach is based on the mixed quantum-classical scheme for spin dynamics, with coupled equations of motions for the quantum subsystem, representing the host, and the localized spins of magnetic dopants, which are treated classically. In the case of a single Mn impurity, we calculate explicitly the time evolution of the Mn spin and the spins of nearest-neighbors As atoms, where the acceptor (hole) state introduced by the Mn dopant resides. We relate the characteristic frequencies in the dynamical spectra to the two dominant energy scales of the system, namely the spin-orbit interaction strength and the value of the p-d exchange coupling between the impurity spin and the host carriers. For a pair of Mn impurities, we find signatures of the indirect (carrier-mediated) exchange interaction in the time evolution of the impurity spins. Finally, we examine temporal correlations between the two Mn spins and their dependence on the exchange coupling and spin-orbit interaction strength, as well as on the initial spin-configuration and separation between the impurities. Our results provide insight into the dynamic interaction between localized magnetic impurities in a nano-scaled magnetic-semiconductor sample, in the extremely dilute (solotronics) regime.