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

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.

accepted for publication in Appl. Phys. Lett

References in corpus (7)

• Valley polarization in MoS2 monolayers by optical pumping
• Substrate-induced band gap opening in epitaxial graphene
• Observation of giant bandgap renormalization and excitonic effects in a monolayer transition metal dichalcogenide semiconductor
• Direct observation of the transition from indirect to direct bandgap in atomically thin epitaxial MoSe2
• Optical signature of symmetry variations and spin-valley coupling in atomically thin tungsten dichalcogenides
• Direct observation of spin-polarised bulk bands in an inversion-symmetric semiconductor
• Observation of monolayer valence band spin-orbit effect and induced quantum well states (QWS) in MoX2

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• Monolayer VTe2: Incommensurate Fermi surface nesting and suppression of charge density waves
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• Spin splitting and strain in epitaxial monolayer WSe${}_2$ on graphene
• Visualizing giant ferroelectric gating effects in large-scale WSe${}_2$/BiFeO${}_3$ heterostructures
• Nearly-free-electron system of monolayer Na on the surface of single-crystal HfSe${}_2$
• Selective Fabrication of Monolayer 1H- and 1T'-WTe2
• Non-degenerate valleys in the half-metallic ferromagnet Fe/WS${}_2$
• Unusual temperature dependence of the band structure associated with local atomic distortion in monolayer 1T'-WTe2