Tunable g factor and phonon-mediated hole spin relaxation in Ge/Si nanowire quantum dots

TL;DR

This paper theoretically investigates the g factor anisotropy and phonon-mediated hole spin relaxation in Ge/Si nanowire quantum dots, revealing tunable properties and optimal conditions for long spin coherence times.

Contribution

It provides a detailed theoretical analysis of g factor tunability and spin relaxation times in Ge/Si nanowire quantum dots, highlighting electric field control and optimal geometries for enhanced spin coherence.

Findings

Large anisotropy of g factor tunable by electric fields

Proposed setup achieving T1 of tens of milliseconds

Longer T1 with increased shell thickness or confinement length

Abstract

We theoretically consider g factor and spin lifetimes of holes in a longitudinal Ge/Si core/shell nanowire quantum dot that is exposed to external magnetic and electric fields. For the ground states, we find a large anisotropy of the g factor which is highly tunable by applying electric fields. This tunability depends strongly on the direction of the electric field with respect to the magnetic field. We calculate the single-phonon hole spin relaxation times T1 for zero and small electric fields and propose an optimal setup in which very large T1 of the order of tens of milliseconds can be reached. Increasing the relative shell thickness or the longitudinal confinement length further prolongs T1. In the absence of electric fields, the dephasing vanishes and the decoherence time T2 is determined by T2 = 2 T1.