Effective theory of monolayer TMDC double quantum dots

TL;DR

This paper develops a theoretical effective model for double quantum dots in monolayer TMDCs, analyzing various scenarios including spin-orbit effects and valley splitting, and shows the low energy behavior resembles a Heisenberg exchange Hamiltonian.

Contribution

It introduces a comprehensive effective theory for TMDC double quantum dots, accounting for different physical effects and simplifying to a Heisenberg model in certain regimes.

Findings

Low energy states can be described by a Heisenberg exchange Hamiltonian.

Different spin-orbit splittings affect the low energy subspace.

Valley degeneracy lifting influences the quantum dot behavior.

Abstract

Monolayer Transition Metal Dichalcogenides (TMDCs) are promising candidates for quantum technologies, such as quantum dots, because they are truly two-dimensional semiconductors with a direct band gap. In this work, we analyse theoretically the behaviour of a double quantum dot (DQD) system created in the conduction band of these materials, with two electrons in the (1,1) charge configuration. Motivated by recent experimental progress, we consider several scenarios, including different spin-orbit splittings in the two dots and including the case when the valley degeneracy is lifted due to an insulating ferromagnetic substrate. Finally, we discuss in which cases it is possible to reduce the low energy subspace to the lowest Kramers pairs. We find that in this case the low energy model is formally identical to the Heisenberg exchange Hamiltonian.