Measurements of a fast nuclear spin dynamics in a single InAs quantum dot with positively charged exciton

TL;DR

This study measures the rapid nuclear spin polarization dynamics in a single InAs quantum dot, revealing the roles of dipolar interactions and electron/hole interactions in nuclear spin decay times at low temperature.

Contribution

It introduces a time-resolved spectroscopy technique to quantify nuclear spin buildup and decay times, highlighting the effects of magnetic fields and carrier interactions in quantum dots.

Findings

Nuclear dipole-dipole interaction causes depolarization with a 500 μs time constant.

External magnetic field extends nuclear spin decay to about 5 ms.

Hole-induced depolarization occurs with a 112 ms time constant.

Abstract

By using highly time-resolved spectroscopy with an alternative {\sigma}+/{\sigma} - laser pulse modulation technique, we are able to measure the fast buildup and decay times of the dynamical nuclear spin polarization (DNSP) at 5 K for a single InAs quantum dot (QD) with positively charged exciton. It is shown that the nuclear dipole-dipole interaction can efficiently depolarize DNSP with a typical time constant of 500 {\mu}s in the absence of external magnetic field. By using an external field of 8 mT to suppress the nuclear dipolar interaction, the decay time turns to be mainly induced by interaction with unpaired electron and extends to about 5 ms. In addition, it is found that the time constant of hole-induced depolarization of nuclear spin is about 112 ms.