Suppressing spin relaxation in silicon

TL;DR

Applying uniaxial strain along the [001] direction in silicon significantly reduces spin relaxation by suppressing dominant scattering mechanisms, leading to nearly three orders of magnitude longer spin relaxation times at low temperatures.

Contribution

This work provides a comprehensive model of spin relaxation in strained silicon, highlighting the suppression of scattering mechanisms and predicting substantial improvements in spin lifetime.

Findings

Spin relaxation time in silicon can be increased by nearly three orders of magnitude.

Uniaxial strain redistributes electrons into two valleys, reducing scattering.

The model accounts for impurity and phonon interactions affecting spin relaxation.

Abstract

Uniaxial compressive strain along the [001] direction strongly suppresses the spin relaxation in silicon. When the strain level is large enough so that electrons are redistributed only in the two valleys along the strain axis, the dominant scattering mechanisms are quenched and electrons mainly experience intra-axis scattering processes (intravalley or intervalley scattering within valleys on the same crystal axis). We first derive the spin-flip matrix elements due to intra-axis electron scattering off impurities, and then provide a comprehensive model of the spin relaxation time due to all possible interactions of conduction-band electrons with impurities and phonons. We predict nearly three orders of magnitude improvement in the spin relaxation time of $\sim10^{19}\text{cm}^{-3}$ antimony-doped silicon (Si:Sb) at low temperatures.