Enhanced valley splitting in monolayer WSe2 due to magnetic exchange field

TL;DR

This paper demonstrates significantly enhanced valley splitting in monolayer WSe2 using magnetic exchange fields from a ferromagnetic EuS substrate, advancing valley control for potential valleytronic and quantum computing applications.

Contribution

The study introduces a method to greatly increase valley splitting in monolayer WSe2 via interfacial magnetic exchange fields from EuS, surpassing previous Zeeman splitting limits.

Findings

Achieved 2.5 meV valley splitting at 1 T

Splitting follows EuS magnetization, confirming MEF influence

Potential for valleytronic and quantum computing applications

Abstract

Exploiting the valley degree of freedom to store and manipulate information provides a novel paradigm for future electronics. A monolayer transition metal dichalcogenide (TMDC) with broken inversion symmetry possesses two degenerate yet inequivalent valleys, offering unique opportunities for valley control through helicity of light. Lifting the valley degeneracy by Zeeman splitting has been demonstrated recently, which may enable valley control by a magnetic field. However, the realized valley splitting is modest, (~ 0.2 meV/T). Here we show greatly enhanced valley spitting in monolayer WSe2, utilizing the interfacial magnetic exchange field (MEF) from a ferromagnetic EuS substrate. A valley splitting of 2.5 meV is demonstrated at 1 T by magneto-reflectance measurements. Moreover, the splitting follows the magnetization of EuS, a hallmark of the MEF. Utilizing MEF of a magnetic insulator can induce magnetic order, and valley and spin polarization in TMDCs, which may enable valleytronic and quantum computing applications.