Hyperfine coupling of hole and nuclear spins in symmetric GaAs quantum dots

TL;DR

This study investigates the hyperfine coupling between hole and nuclear spins in symmetric GaAs quantum dots, revealing a weaker hole-nuclear interaction and how it can be engineered via dot shape and size for improved spin coherence.

Contribution

It provides experimental measurements and theoretical analysis of hole-nuclear hyperfine interaction in symmetric GaAs quantum dots, highlighting the influence of dot geometry and carrier confinement.

Findings

Hole hyperfine interaction is about five times weaker than electron hyperfine interaction.

Four resolved photoluminescence lines enable separate measurement of electron and hole contributions.

Hyperfine coupling ratio depends on material properties, dot shape, and heavy-hole mixing.

Abstract

In self assembled III-V semiconductor quantum dots, valence holes have longer spin coherence times than the conduction electrons, due to their weaker coupling to nuclear spin bath fluctuations. Prolonging hole spin stability relies on a better understanding of the hole to nuclear spin hyperfine coupling which we address both in experiment and theory in the symmetric (111) GaAs/AlGaAs droplet dots. In magnetic fields applied along the growth axis, we create a strong nuclear spin polarization detected through the positively charged trion X$^+$ Zeeman and Overhauser splittings. The observation of four clearly resolved photoluminescence lines - a unique property of the (111) nanosystems - allows us to measure separately the electron and hole contribution to the Overhauser shift. The hyperfine interaction for holes is found to be about five times weaker than that for electrons. Our theory shows that this ratio depends not only on intrinsic material properties but also on the dot shape and carrier confinement through the heavy-hole mixing, an opportunity for engineering the hole-nuclear spin interaction by tuning dot size and shape.