Theory of spin waves in diluted-magnetic-semiconductor quantum wells

TL;DR

This paper develops a theoretical framework for understanding collective spin excitations in diluted-magnetic-semiconductor quantum wells, revealing unique dispersion behaviors and the effects of spin-orbit interactions.

Contribution

It introduces a novel theory describing spin wave dynamics in diluted-magnetic-semiconductor quantum wells, including effects of spin polarization and spin-orbit coupling.

Findings

Goldstone mode exhibits anomalous $k^4$ dispersion

Odd parity modes do not disperse in symmetric wells

Spin-orbit interactions open a gap in the excitation spectrum

Abstract

We present a theory of collective spin excitations in diluted-magnetic-semiconductor quantum wells in which local magnetic moments are coupled via a quasi-two-dimensional gas of electrons or holes. In the case of a ferromagnetic state with partly spin-polarized electrons, we find that the Goldstone collective mode has anomalous $k^4$ dispersion and that for symmetric quantum wells odd parity modes do not disperse at all. We discuss the gap in the collective excitation spectrum which appears when spin-orbit interactions are included.