Single-shot measurement of transient nuclear magnetization with spin-noise spectroscopy in n-GaAs microcavities

TL;DR

This paper demonstrates a single-shot spin noise spectroscopy method to observe nuclear spin polarization dynamics in n-GaAs microcavities, revealing build-up and relaxation of nuclear magnetization with high temporal resolution.

Contribution

It introduces a novel single-shot SNS technique to directly measure nuclear spin polarization dynamics in semiconductor microcavities.

Findings

Nuclear polarization causes a measurable shift in electron spin noise spectrum.

The nuclear spin relaxation time was observed to be hundreds of seconds.

Elliptically polarized light can induce nuclear polarization even at nominal transparency.

Abstract

We exploit spin noise spectroscopy (SNS) to directly observe build-up of dynamic nuclear polarization and relaxation of a perturbed nuclear spin-system to its equilibrium state in a single-shot experiment. The SNS experiments were performed on a layer of bulk $n$-type GaAs embedded into a high-finesse microcavity with negative detuning. The dynamic nuclear spin polarization is observed as a shift of the peak in the electron spin noise spectrum due to the build-up of the Overhauser field acting on the electron spin. The relaxation dynamics of nuclear spin system was revealed in the time-resolved SNS experiments where the exponential decay of the Overhauser field with characteristic timescale of hundreds of seconds was detected. We show that elliptically polarized laser beam tuned in resonance with the cavity mode, whose energy corresponds to nominal transparency of the semiconductor, can nevertheless produce a sizable nuclear polarization.