Controllable electron spin dephasing due to phonon state distinguishability in a coupled quantum dot system

TL;DR

This paper predicts a controllable spin dephasing mechanism in coupled quantum dots caused by phonon distinguishability due to g-factor mismatch, which can limit spin coherence times at cryogenic temperatures.

Contribution

It introduces a novel phonon-related spin dephasing channel caused by g-factor mismatch, with potential for external control in quantum dot systems.

Findings

Dephasing is caused by phonon distinguishability due to g-factor mismatch.

The dephasing mechanism can be controlled by dot size, composition, and external fields.

This mechanism may significantly limit spin coherence times at cryogenic temperatures.

Abstract

We predict a spin pure dephasing channel in electron relaxation between states with unequal Zeeman splittings, exemplified by a spin-preserving electron tunneling between quantum dots in a magnetic field. The dephasing is caused by a mismatch in electron $g$-factors in the dots leading to distinguishability of phonons emitted during tunneling with opposite spins. Combining multiband $\boldsymbol{k}{\cdot}\boldsymbol{p}$ modeling and dynamical simulations via a Master equation we show that this fundamental effect of spin measurement effected by the phonon bath may be widely controlled by the size and composition of the dots or on demand, via tuning of external fields. By comparing the numerically simulated degree of dephasing with the predictions of general theory based on distinguishability of environment states, we show that the proposed mechanism is the dominant phonon-related spin dephasing channel and may limit spin coherence time in tunnel-coupled structures at cryogenic temperatures.