Mapping of spin lifetimes to electronic states in n-type GaAs near the metal-insulator transition

TL;DR

This study investigates how spin lifetimes vary with electronic states in n-GaAs near the metal-insulator transition, revealing that delocalized donor band states have the longest spin lifetimes exceeding 100 ns.

Contribution

It identifies the specific electronic states associated with long spin lifetimes in n-GaAs near the metal-insulator transition using time-resolved Kerr rotation.

Findings

Longest spin lifetimes (>100 ns) are linked to delocalized donor band states.

Localized donor band states show short spin lifetimes (~300 ps).

Occupation of donor states causes a distinct Overhauser shift.

Abstract

The longest spin lifetimes in bulk n-GaAs exceed 100 ns for doping concentrations near the metal-insulator transition (J.M. Kikkawa, D.D. Awschalom, Phys. Rev. Lett. 80, 4313 (1998)). The respective electronic states have yet not been identified. We therefore investigate the energy dependence of spin lifetimes in n-GaAs by time-resolved Kerr rotation. Spin lifetimes vary by three orders of magnitude as a function of energy when occupying donor and conduction band states. The longest spin lifetimes (>100 ns) are assigned to delocalized donor band states, while conduction band states exhibit shorter spin lifetimes. The occupation of localized donor band states is identified by short spin lifetimes (~300 ps) and a distinct Overhauser shift due to dynamic nuclear polarization.