Influence of non-magnetic impurity scattering on the spin dynamics in diluted magnetic semiconductors

TL;DR

This paper investigates how non-magnetic impurity scattering influences spin dynamics in diluted magnetic semiconductors, revealing suppression of non-Markovian effects and significant correlation-induced modifications under optical excitation.

Contribution

It introduces a quantum kinetic model that incorporates non-magnetic scattering, showing its impact on spin dynamics and correlation effects in Mn-doped CdTe.

Findings

Non-magnetic impurity scattering suppresses non-Markovian effects.

Carrier redistribution in k-space is enabled by impurity correlations.

Strong correlations alter long-time spin polarization and precession frequencies.

Abstract

The doping of semiconductors with magnetic impurities gives rise not only to a spin-spin interaction between quasi-free carriers and magnetic impurities, but also to a local spin-independent disorder potential for the carriers. Based on a quantum kinetic theory for the carrier and impurity density matrices as well as the magnetic and non-magnetic carrier-impurity correlations, the influence of the non-magnetic scattering potential on the spin dynamics in DMS after optical excitation with circularly polarized light is investigated using the example of Mn-doped CdTe. It is shown that non-Markovian effects, which are predicted in calculations where only the magnetic carrier-impurity interaction is accounted for, can be strongly suppressed in the presence of non-magnetic impurity scattering. This effect can be traced back to a significant redistribution of carriers in $\mathbf{k}$-space which is enabled by the build-up of large carrier-impurity correlation energies. A comparison with the Markov limit of the quantum kinetic theory shows that, in the presence of an external magnetic field parallel to the initial carrier polarization, the asymptotic value of the spin polarization at long times is significantly different in the quantum kinetic and the Markovian calculations. This effect can also be attributed to the formation of strong correlations which invalidates the semiclassical Markovian picture and it is stronger when the non-magnetic carrier-impurity interaction is accounted for. In an external magnetic field perpendicular to the initial carrier spin, the correlations are also responsible for a renormalization of the carrier spin precession frequency.