Coherent adiabatic theory of two-electron quantum dot molecules in external spin baths

TL;DR

This paper develops a molecular orbital-based theory to model the coherent evolution and decoherence of two-electron quantum dot molecules interacting with nuclear spin baths, aligning well with experimental data.

Contribution

It introduces a new accurate theoretical framework for simulating two-electron quantum dot dynamics including hyperfine interactions and external fields, enabling direct numerical modeling of decoherence.

Findings

Good agreement with recent experimental dephasing data

Faster electric switching can reduce hyperfine-induced mixing

Analytical and numerical models complement each other

Abstract

We derive an accurate molecular orbital based expression for the coherent time evolution of a two-electron wave function in a quantum dot molecule where the electrons interact with each other, with external time dependent electromagnetic fields and with a surrounding nuclear spin reservoir. The theory allows for direct numerical modeling of the decoherence in quantum dots due to hyperfine interactions. Calculations result in good agreement with recent singlet-triplet dephasing experiments by Laird et. al. [Phys. Rev. Lett. 97, 056801 (2006)], as well as analytical model calculations. Furthermore, it is shown that using a much faster electric switch than applied in these experiments will transfer the initial state to excited states where the hyperfine singlet-triplet mixing is negligible.