Asymmetric exchange between electron spins in coupled semiconductor quantum dots

TL;DR

This paper provides a detailed microscopic analysis of asymmetric exchange interactions between electron spins in coupled semiconductor quantum dots, highlighting a small but significant contribution relevant for quantum information applications.

Contribution

It introduces a third-order asymmetric exchange term arising from band mixing and Coulomb interaction, independent of crystal inversion asymmetry, with detailed evaluations for quantum dot systems.

Findings

Asymmetric exchange contribution is about 0.001 of isotropic exchange.

The asymmetric term depends on spin and orbital motion coupling.

Results are relevant for quantum information processing.

Abstract

We obtain a microscopic description of the interaction between electron spins in bulk semiconductors and in pairs of semiconductor quantum dots. Treating the k.p band mixing and the Coulomb interaction on the same footing, we obtain in the third order an asymmetric contribution to the exchange interaction arising from the coupling between the spin of one electron and the relative orbital motion of the other. This contribution does not depend on the inversion asymmetry of the crystal. We find that it is ~0.001 of the isotropic exchange, which is of interest in quantum information. Detailed evaluations are given for several quantum dot systems.