Electron spin-phonon interaction symmetries and tunable spin relaxation in silicon and germanium

TL;DR

This paper analyzes the symmetries of electron-phonon interactions in silicon and germanium, revealing how spin relaxation times can be tuned via strain or quantum confinement, with implications for spintronic applications.

Contribution

It identifies the symmetries of electron-phonon interactions in silicon and germanium and quantifies how spin lifetimes can be tuned through valley degeneracy control.

Findings

Room-temperature spin lifetimes in silicon are comparable to gallium arsenide.

Spin lifetimes can be tuned by reducing valley degeneracy.

Tuning range is limited to slightly over an order of magnitude.

Abstract

Compared with direct-gap semiconductors, the valley degeneracy of silicon and germanium opens up new channels for spin relaxation that counteract the spin degeneracy of the inversion-symmetric system. Here the symmetries of the electron-phonon interaction for silicon and germanium are identified and the resulting spin lifetimes are calculated. Room-temperature spin lifetimes of electrons in silicon are found to be comparable to those in gallium arsenide, however, the spin lifetimes in silicon or germanium can be tuned by reducing the valley degeneracy through strain or quantum confinement. The tunable range is limited to slightly over an order of magnitude by intravalley processes.