# Phonon-assisted carrier tunneling in coupled quantum dot systems with hyperfine-induced spin flip

## TL;DR

This paper investigates phonon-assisted hyperfine spin flips during electron and hole tunneling in coupled quantum dots, revealing the dominance of hyperfine processes over spin-orbit relaxation under certain magnetic field conditions and proposing experimental tests for hyperfine coupling effects.

## Contribution

It provides a detailed calculation of hyperfine-induced spin flip rates in quantum dot tunneling, highlighting the conditions where hyperfine interactions dominate over spin-orbit effects and suggesting experimental verification methods.

## Key findings

- Hyperfine processes dominate over spin-orbit relaxation for electrons up to a few Tesla.
- For holes, hyperfine dominance occurs at sub-Tesla magnetic fields due to valence band hyperfine coupling.
- A minimum in spin-flip probability arises from the interplay of hyperfine and spin-orbit mechanisms.

## Abstract

We calculate the rates of phonon-assisted hyperfine spin flips during electron and hole tunneling between quantum dots in a self-assembled quantum dot molecule. We show that the hyperfine process dominates over the spin-orbit-induced spin relaxation in magnetic fields up to a few Tesla for electrons, while for holes this cross-over takes place at field magnitudes of a fraction of Tesla, upon the assumption of a large $d$-shell admixture to the valence band state, resulting in a strong transverse hyperfine coupling. The interplay of the two spin-flip mechanisms leads to a minimum of the spin-flip probability, which is in principle experimentally measurable and can be used as a test for the presence of substantial transverse hyperfine couplings in the valence band.