Intervalley coupling by quantum dot confinement potentials in monolayer transition metal dichalcogenides

TL;DR

This study systematically investigates intervalley coupling in monolayer TMD quantum dots, finding it generally weak and tunable, thus preserving the valley physics of the bulk material for potential quantum information applications.

Contribution

It provides a detailed analysis of how quantum dot confinement affects valley hybridization, revealing weak coupling and potential for external tuning in monolayer TMDs.

Findings

Intervalley coupling is generally weak due to boundary wavefunction vanishing.

Valley physics of the bulk is preserved in the quantum dots.

Intervalley coupling can be tuned by external controls.

Abstract

Monolayer transition metal dichalcogenides (TMDs) offer new opportunities for realizing quantum dots (QDs) in the ultimate two-dimensional (2D) limit. Given the rich control possibilities of electron valley pseudospin discovered in the monolayers, this quantum degree of freedom can be a promising carrier of information for potential quantum spintronics exploiting single electrons in TMD QDs. An outstanding issue is to identify the degree of valley hybridization, due to the QD confinement, which may significantly change the valley physics in QDs from its form in the 2D bulk. Here we perform a systematic study of the intervalley coupling by QD confinement potentials on extended TMD monolayers. We find that the intervalley coupling in such geometry is generically weak due to the vanishing amplitude of the electron wavefunction at the QD boundary, and hence valley hybridization shall be well quenched by the much stronger spin-valley coupling in monolayer TMDs and the QDs can well inherit the valley physics of the 2D bulk. We also discover sensitive dependence of intervalley coupling strength on the central position and the lateral length scales of the confinement potentials, which may possibly allow tuning of intervalley coupling by external controls