Measurement of heavy-hole spin dephasing in (InGa)As quantum dots

TL;DR

This study measures the spin dephasing times of holes in (InGa)As quantum dots using spin noise spectroscopy, revealing two distinct relaxation times linked to hole spin orientation and the impact of light absorption.

Contribution

It provides the first detailed measurement of heavy-hole spin dephasing times in quantum dots and analyzes the effects of nuclear interactions and light absorption on spin dynamics.

Findings

Short spin relaxation time of 27 ns for heavy holes.

Existence of a longer, over 270 ns, spin relaxation time.

Light absorption suppresses spin noise signals despite low laser intensity.

Abstract

We measure the spin dephasing of holes localized in self-assembled (InGa)As quantum dots by spin noise spectroscopy. The localized holes show a distinct hyperfine interaction with the nuclear spin bath despite the p-type symmetry of the valence band states. The experiments reveal a short spin relaxation time {\tau}_{fast}^{hh} of 27 ns and a second, long spin relaxation time {\tau}_{slow}^{hh} which exceeds the latter by more than one order of magnitude. The two times are attributed to heavy hole spins aligned perpendicular and parallel to the stochastic nuclear magnetic field. Intensity dependent measurements and numerical simulations reveal that the long relaxation time is still obscured by light absorption, despite low laser intensity and large detuning. Off-resonant light absorption causes a suppression of the spin noise signal due to the creation of a second hole entailing a vanishing hole spin polarization.