Theory of Electron Spin Relaxation in ZnO

TL;DR

This paper investigates the spin relaxation mechanisms in doped ZnO, revealing non-monotonic temperature dependence and the influence of spin-orbit coupling, with implications for spintronics and material characterization.

Contribution

It provides a theoretical explanation for the non-monotonic spin lifetime behavior in ZnO and demonstrates how optical orientation can characterize impurity properties.

Findings

Spin lifetime shows non-monotonic temperature dependence.

Spin exchange between localized and extended states explains behavior.

Optical orientation can be used to determine impurity energies and densities.

Abstract

Doped ZnO is a promising material for spintronics applications. For such applications, it is important to understand the spin dynamics and particularly the spin coherence of this II-VI semiconductor. The spin lifetime $\tau_{s}$ has been measured by optical orientation experiments, and it shows a surprising non-monotonic behavior with temperature. We explain this behavior by invoking spin exchange between localized and extended states. Interestingly, the effects of spin-orbit coupling are by no means negligible, in spite of the relatively small valence band splitting. This is due to the wurtzite crystal structure of ZnO. Detailed analysis allows us to characterize the impurity binding energies and densities, showing that optical orientation experiments can be used as a characterization tool for semiconductor samples.