Electron Spin Dephasing and Optical Pumping of Nuclear Spins in GaN

TL;DR

This study investigates electron spin dephasing and nuclear spin polarization in cubic GaN, revealing how magnetic fields influence spin coherence and demonstrating optical nuclear spin pumping in GaN-based systems.

Contribution

First demonstration of optical nuclear spin pumping in GaN, with detailed measurements of electron spin dephasing and hyperfine interactions.

Findings

Electron spin dephasing time is about 1.5 ns without magnetic field.

Applying a small magnetic field significantly increases spin coherence.

Optical pumping induces measurable nuclear polarization in GaN.

Abstract

We have measured the donor-bound electron spin dynamics in cubic GaN by time-resolved Kerr rotation experiments. The ensemble electron spin dephasing time in this quantum dot like system characterized by a Bohr radius of 2.5 nm is of the order of 1.5 ns as a result of the interaction with the fluctuating nuclear spins. It increases drastically when an external magnetic field as small as 10 mT is applied. We extract a dispersion of the nuclear hyperfine field {\delta}Bn $\sim$ 4 mT, in agreement with calculations. We also demonstrate for the first time in GaN based systems the optical pumping of nuclear spin yielding the build-up of a significant nuclear polarization.