Spin relaxation in wurtzite nanowires

TL;DR

This paper provides a theoretical analysis of spin relaxation mechanisms in wurtzite nanowires, highlighting the dominance of $k$-cubic spin-orbit effects on spin lifetime and their influence on quantum conductivity corrections.

Contribution

It reveals that in finite-size nanowires, spin lifetime is mainly governed by $k$-cubic terms, contrasting with bulk behavior dominated by $k$-linear contributions.

Findings

Spin lifetime is determined by $k$-cubic spin-orbit terms.

Magnetoconductance correction is insensitive to wire radius.

Optical measurements show significant variation in spin lifetime.

Abstract

We theoretically investigate the D'yakonov-Perel' spin relaxation properties in diffusive wurtzite semiconductor nanowires and their impact on the quantum correction to the conductivity. Although the lifetime of the long-lived spin states is limited by the dominant $k$-linear spin-orbit contributions in the bulk, these terms show almost no effect in the finite-size nanowires. Here, the spin lifetime is essentially determined by the small $k$-cubic spin-orbit terms and nearly independent of the wire radius. At the same time, these states possess in general a complex helical structure in real space that is modulated by the spin precession length induced by the $k$-linear terms. For this reason, the experimentally detected spin relaxation largely depends on the ratio between the nanowire radius and the spin precession length as well as the type of measurement. In particular, it is shown that while a variation of the radius hardly affects the magnetoconductance correction, which is governed by the long-lived spin states, the change in the spin lifetime observed in optical experiments can be dramatic. We compare our results with recent experimental studies on wurtzite InAs nanowires.