Spin- and valley- coupled electronic states in monolayer WSe2 on bilayer graphene

TL;DR

This study demonstrates the fabrication of high-quality monolayer WSe2 on bilayer graphene, revealing giant spin splitting and direct bandgap properties that highlight its potential for spin- and valley-based electronic devices.

Contribution

The paper reports the epitaxial growth of monolayer WSe2 on bilayer graphene and characterizes its unique spin- and valley-coupled electronic states using photoemission spectroscopy.

Findings

Direct energy gap at Brillouin-zone corner in monolayer WSe2

Giant spin splitting of ~0.5 eV observed

Potential for advanced spin- and valleytronic devices

Abstract

We have fabricated a high-quality monolayer WSe2 film on bilayer graphene by epitaxial growth, and revealed the electronic states by spin- and angle-resolved photoemission spectroscopy. We observed a direct energy gap at the Brillounin-zone corner in contrast to the indirect nature of gap in bulk WSe2, which is attributed to the lack of interlayer interaction and the breaking of space-inversion symmetry in monolayer film. A giant spin splitting of ~0.5 eV, which is the largest among known monolayer transition-metal dichalcogenides, is observed in the energy band around the zone corner. The present results suggest a high potential applicability of WSe2 to develop advanced devices based with the coupling of spin- and valley-degrees of freedom.