Spin-3/2 physics of semiconductor hole nanowires: Valence-band mixing and tunable interplay between bulk-material and orbital bound-state spin splittings

TL;DR

This paper provides a comprehensive theoretical analysis of hole quantum wires, highlighting how quantum confinement, shape, and crystal symmetry influence spin properties and g factors, with implications for spintronics.

Contribution

It offers new insights into the interplay between valence-band mixing, wire geometry, and spin splittings, enabling tunable hole-spin states in semiconductor nanowires.

Findings

Subband-edge g factors vary significantly due to spin-3/2 character.

Low-lying subband edges show robustness against shape changes.

Aspect ratio tuning allows in-situ control of hole-spin properties.

Abstract

We present a detailed theoretical study of the electronic spectrum and Zeeman splitting in hole quantum wires. The spin-3/2 character of the topmost bulk-valence-band states results in a strong variation of subband-edge g factors between different subbands. We elucidate the interplay between quantum confinement and heavy-hole - light-hole mixing and identify a certain robustness displayed by low-lying hole-wire subband edges with respect to changes in the shape or strength of the wire potential. The ability to address individual subband edges in, e.g., transport or optical experiments enables the study of holes states with nonstandard spin polarization, which do not exist in spin-1/2 systems. Changing the aspect ratio of hole wires with rectangular cross-section turns out to strongly affect the g factor of subband edges, providing an opportunity for versatile in-situ tuning of hole-spin properties with possible application in spintronics. The relative importance of cubic crystal symmetry is discussed, as well as the spin splitting away from zone-center subband edges.