Electric-field-tunable valley Zeeman effect in bilayer graphene heterostructures: Realization of the spin-orbit valve effect

Abstract

We report the discovery of electric-field-induced transition from a topologically trivial to a topologically nontrivial band structure in an atomically sharp heterostructure of bilayer graphene (BLG) and single-layer WSe2 per the theoretical predictions of Gmitra and Fabian [Phys. Rev. Lett. 119, 146401 (2017)]. Through detailed studies of the quantum correction to the conductance in the BLG, we establish that the band-structure evolution arises from an interplay between proximity-induced strong spin-orbit interaction (SOI) and the layer polarizability in BLG. The low-energy carriers in the BLG experience an effective valley Zeeman SOI that is completely gate tunable to the extent that it can be switched on or off by applying a transverse displacement field or can be controllably transferred between the valence and the conduction band. We demonstrate that this results in the evolution from weak localization to weak antilocalization at a constant electronic density as the net displacement field is tuned from a positive to a negative value with a concomitant SOI-induced splitting of the low-energy bands of the BLG near the K (K') valley, which is a unique signature of the theoretically predicted spin-orbit valve effect. Our analysis shows that quantum correction to the Drude conductance in Dirac materials with strong induced SOI can only be explained satisfactorily by a theory that accounts for the SOI-induced spin splitting of the BLG low-energy bands. Our results demonstrate the potential for achieving highly tunable devices based on the valley Zeeman effect in dual-gated two-dimensional materials.

5 pages, 5 figures

References in corpus (7)

• 2D materials and van der Waals heterostructures
• The electronic properties of bilayer graphene
• Spin-orbit driven band inversion in bilayer graphene by van der Waals proximity effect
• Proximity effects in bilayer graphene on monolayer WSe${}_2$: Field-effect spin-valley locking, spin-orbit valve, and spin transistor
• Optimal charge-to-spin conversion in graphene on transition metal dichalcogenides
• Spin transport in high-mobility graphene on WS${}_2$ substrate with electric-field tunable proximity spin-orbit interaction
• Spin-valley relaxation and quantum transport regimes in two-dimensional transition metal dichalcogenides

Cited by in corpus (4)

• Proximity spin-orbit and exchange coupling in ABA and ABC trilayer graphene van der Waals heterostructures
• Experimental observation of spin-split energy dispersion in high-mobility single-layer graphene/WSe2 heterostructures
• Valley-Polarized Quantum Anomalous Hall Phase in Bilayer Graphene with Layer-Dependent Proximity Effects
• Proximity spin-orbit coupling in graphene on alloyed transition metal dichalcogenides