Anisotropy-driven spin relaxation in germanium

TL;DR

This paper uncovers a novel spin relaxation mechanism in germanium caused by g-factor anisotropy and intervalley scattering, enabling new methods to measure long spin lifetimes in germanium devices.

Contribution

It introduces a previously unobserved anisotropy-driven spin relaxation mechanism in germanium and demonstrates how to extract spin lifetimes from spin-valve measurements without precession.

Findings

Spin lifetimes in Ge reach hundreds of nanoseconds at low temperature.

The relaxation mechanism is driven by g-factor anisotropy and intervalley scattering.

Spin lifetime measurements are possible without spin precession in certain regimes.

Abstract

A unique spin depolarization mechanism, induced by the presence of g-factor anisotropy and intervalley scattering, is revealed by spin transport measurements on long-distance germanium devices in a longitudinal magnetic field. The confluence of electron-phonon scattering (leading to Elliott-Yafet spin flips) and this previously unobserved physics enables the extraction of spin lifetime solely from spin-valve measurements, without spin precession, and in a regime of substantial electric-field-generated carrier heating. We find spin lifetimes in Ge up to several hundreds of ns at low temperature, far beyond any other available experimental results.