Ultrafast spin dynamics in II-VI diluted magnetic semiconductors with spin-orbit interaction

TL;DR

This paper theoretically investigates the ultrafast spin dynamics in II-VI diluted magnetic semiconductors, focusing on the interplay between exchange $sd$-coupling and spin-orbit interaction in bulk and quantum well systems, revealing oscillatory behaviors and the limitations of mean-field approximation.

Contribution

It introduces a formalism that incorporates electronic correlations beyond mean-field theory to analyze spin dynamics influenced by both exchange and spin-orbit interactions.

Findings

Both interactions can dominate or compete depending on system parameters.

Spin-orbit interaction causes strong oscillations in spin dynamics.

Mean-field approximation suppresses spin-orbit-induced dephasing.

Abstract

We study theoretically the ultrafast spin dynamics of II-VI diluted magnetic semiconductors in the presence of spin-orbit interaction. Our goal is to explore the interplay or competition between the exchange $sd$-coupling and the spin-orbit interaction in both bulk and quantum well systems. For bulk materials we concentrate on Zn$_{1-x}$Mn$_x$Se and take into account the Dresselhaus interaction, while for quantum wells we examine Hg$_{1-x-y}$Mn$_x$Cd$_y$Te systems with a strong Rashba coupling. Our calculations were performed with a recently developed formalism which incorporates electronic correlations beyond mean-field theory originated from the exchange $sd$-coupling. For both bulk and quasi-two-dimensional systems we find that, by varying the system parameters within realistic ranges, both interactions can be chosen to play a dominant role or to compete on an equal footing with each other. The most notable effect of the spin-orbit interaction in both types of systems is the appearance of strong oscillations where the exchange $sd$-coupling by itself only causes an exponential decay of the mean electronic spin components. The mean-field approximation is also studied and it is interpreted analytically why it shows a strong suppression of the spin-orbit-induced dephasing of the spin component parallel to the Mn magnetic field.