Impurity-assisted electric control of spin-valley qubits in monolayer MoS$_2$

TL;DR

This paper proposes a method to electrically control spin-valley qubits in monolayer MoS$_2$ using impurities and magnetic fields, enabling in-plane electric manipulation of the qubit states.

Contribution

It introduces a novel impurity-assisted mechanism for electrically controlling spin-valley qubits in monolayer transition metal dichalcogenides.

Findings

Impurities enable coupling between qubit basis states for control.

The in-plane g-factor becomes nonzero due to impurity effects.

The mechanism shows unconventional features from symmetry-forbidden intervalley scattering.

Abstract

We theoretically study a single-electron spin-valley qubit in an electrostatically defined quantum dot in a transition metal dichalcogenide monolayer, focusing on the example of MoS$_2$. Coupling of the qubit basis states for coherent control is challenging, as it requires a simultaneous flip of spin and valley. Here, we show that a tilted magnetic field together with a short-range impurity, such as a vacancy, a substitutional defect, or an adatom, can give rise to a coupling between the qubit basis states. This mechanism renders the in-plane $g$-factor nonzero, and allows to control the qubit with an in-plane ac electric field, akin to electrically driven spin resonance. We evaluate the dependence of the in-plane $g$-factor and the electrically induced qubit Rabi frequency on the type and position of the impurity. We reveal highly unconventional features of the coupling mechanism, arising from symmetry-forbidden intervalley scattering, in the case when the impurity is located at a S site. Our results provide design guidelines for electrically controllable qubits in two-dimensional semiconductors.