Abstract
We study the effect of valence band spin–orbit interactions (SOI) on the acoustic phonon-assisted spin relaxation of holes confined in quantum dots (QDs). Heavy hole–light hole (hh–lh) mixing and all the spin–orbit terms arising from zinc-blende bulk inversion asymmetry (BIA) are considered on equal footing in a fully three-dimensional Hamiltonian. We show that hh–lh mixing and BIA have comparable contributions to the hole spin relaxation in self-assembled QDs, but BIA becomes dominant in gated QDs. Simultaneously accounting for both mechanisms is necessary for quantitatively correct results in quasi-two-dimensional QDs. The dependence of the hole spin relaxation on the QD geometry and spin splitting energy is drastically different from that of electrons, with a non-monotonic behavior which results from the interplay between SOI terms. Our results reconcile contradictory predictions of previous theoretical works and are consistent with experiments.
Highlights
We study the effect of valence band spin–orbit interactions (SOI) on the acoustic phonon-assisted spin relaxation of holes confined in quantum dots (QDs)
Other authors have suggested instead that the splitting between hh and lh subbands in flat QDs is large owing to confinement and strain, so that spin admixture must be due to other SOI mechanisms
We study the hole spin dynamics considering simultaneously the most relevant intrinsic SOI terms of III–V QDs, namely hh–lh mixing and all the different Dresselhaus SOI terms arising from the bulk inversion asymmetry (BIA) of zinc-blende crystals, along with the hole–acoustic phonon coupling
Summary
We study the spin relaxation of holes confined in zinc-blende QDs grown along the [001] direction. The hole spin states are considered split energetically, for example by the e–h exchange interaction in excitons or any other source that can be viewed as an effective axial magnetic field. Similar results can be expected for transitions between Zeeman sublevels under moderate external magnetic fields
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