Control of Exciton Valley Coherence in Transition Metal Dichalcogenide Monolayers

TL;DR

This paper demonstrates the control of exciton valley coherence in monolayer WSe2 using magnetic fields, achieving significant rotation of valley superpositions, which advances potential quantum computing applications based on valley degrees of freedom.

Contribution

It introduces a method to manipulate exciton valley coherence in transition metal dichalcogenide monolayers via magnetic fields, enabling large-angle rotations on picosecond timescales.

Findings

Rotation of valley superposition by up to 30 degrees at 9 T magnetic field

Control of valley coherence on picosecond timescales

Potential for valley-based qubit manipulation

Abstract

The direct gap interband transitions in transition metal dichalcogenides monolayers are governed by chiral optical selection rules. Determined by laser helicity, optical transitions in either the $K^+$ or $K^-$ valley in momentum space are induced. Linearly polarized laser excitation prepares a coherent superposition of valley states. Here we demonstrate the control of the exciton valley coherence in monolayer WSe2 by tuning the applied magnetic field perpendicular to the monolayer plane. We show rotation of this coherent superposition of valley states by angles as large as 30 degrees in applied fields up to 9 T. This exciton valley coherence control on ps time scale could be an important step towards complete control of qubits based on the valley degree of freedom.