Spin-spin coupling in electrostatically coupled quantum dots

TL;DR

This paper investigates a new anisotropic XY spin-spin interaction mechanism between electrostatically coupled quantum dots, influenced by Coulomb and spin-orbit interactions, which can be tuned via magnetic field and dot separation.

Contribution

It introduces a novel spin-spin coupling mechanism in quantum dots without tunneling, dependent on Coulomb and spin-orbit effects, and proposes a measurement scheme.

Findings

Interaction is anisotropic XY type and proportional to Zeeman splitting.

Interaction varies non-monotonically with inter-dot distance and magnetic field.

Interaction can vanish at specific distances and orientations.

Abstract

We study the spin-spin coupling between two single-electron quantum dots due to the Coulomb and spin-orbit interactions, in the absence of tunneling between the dots. We find an anisotropic XY spin-spin interaction that is proportional to the Zeeman splitting produced by the external magnetic field. This interaction is studied both in the limit of weak and strong Coulomb repulsion with respect to the level spacing of the dot. The interaction is found to be a non-monotonic function of inter-dot distance $a_0$ and external magnetic field, and, moreover, vanishes for some special values of $a_0$ and/or magnetic field orientation. This mechanism thus provides a new way to generate and tune spin interaction between quantum dots. We propose a scheme to measure this spin-spin interaction based on the spin-relaxation-measurement technique.