# Closing the gap between spatial and spin dynamics of electrons at the metal-to-insulator transition

## TL;DR

This study combines optical and magneto-transport measurements to comprehensively understand electron spin relaxation mechanisms across the metal-insulator transition in n-doped GaAs, revealing complex interactions and a maximum spin lifetime of over 800 ns.

## Contribution

It provides a complete quantitative model of electron spin relaxation mechanisms across the entire doping regime in GaAs, unifying previously disconnected phenomena.

## Key findings

- Maximum spin lifetime exceeds 800 ns near the MIT
- Deviations from Dyakonov-Perel mechanism at higher doping levels
- Identification of scattering by local conductivity domain boundaries

## Abstract

We combine extensive precision measurements of the optically detected spin dynamics and magneto-transport measurements in a contiguous set of n-doped bulk GaAs structures in order to unambiguously unravel the intriguing but complex contributions to the spin relaxation at the metal-to-insulator transition (MIT). Just below the MIT, the interplay between hopping induced loss of spin coherence and hyperfine interaction yields a maximum spin lifetime exceeding 800~ns. At slightly higher doping concentrations, however, the spin relaxation deviates from the expected Dyakonov-Perel mechanism which is consistently explained by a reduction of the effective motional narrowing with increasing doping concentration. The reduction is attributed to the change of the dominant momentum scattering mechanism in the metallic impurity band where scattering by local conductivity domain boundaries due to the intrinsic random distribution of donors becomes significant. Here, we fully identify and model all intricate contributions of the relevant microscopic scattering mechanisms which allows the complete quantitative modeling of the electron spin relaxation in the entire regime from weakly interacting up to fully delocalized electrons.