Quantum spin Hall edge states and interlayer coupling in twisted-bilayer WTe${}_2$

Abstract

The quantum spin Hall (QSH) effect, characterized by topologically protected spin-polarized edge states, was recently demonstrated in monolayers of the transition metal dichalcogenide (TMD) WTe${}_2$. However, the robustness of this topological protection remains largely unexplored in van der Waals heterostructures containing one or more layers of a QSH insulator. In this work, we use scanning tunneling microscopy and spectroscopy (STM/STS) to explore the topological nature of twisted bilayer (tBL) WTe${}_2$ which is produce from folded monolayers, as well as, tear-and-stack fabrication. At the tBL bilayer edge, we observe the characteristic spectroscopic signature of the QSH edge state that is absent in topologically trivial as-grown bilayer. For small twist angles, a rectangular moiré pattern develops, which results in local modifications of the band structure. Using first principles calculations, we quantify the interactions in tBL WTe${}_2$ and its topological edge states as function of interlayer distance and conclude that it is possible to tune the topology of WTe${}_2$ bilayers via the twist angle as well as interlayer interactions.

References in corpus (24)

• Van der Waals heterostructures
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• Quantum Spin Hall Effect in Graphene
• Correlated Insulator Behaviour at Half-Filling in Magic Angle Graphene Superlattices
• Tuning superconductivity in twisted bilayer graphene
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• Superconductors, Orbital Magnets, and Correlated States in Magic Angle Bilayer Graphene
• Intrinsic quantized anomalous Hall effect in a moiré heterostructure
• Magic continuum in twisted bilayer WSe2
• Realization of Quantum Spin Hall State in Monolayer 1T'-WTe2
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• Topological insulators in twisted transition metal dichalcogenide homobilayers
• Edge conduction in monolayer WTe2
• Electrically Tunable Low Density Superconductivity in a Monolayer Topological Insulator
• Gate-induced superconductivity in a monolayer topological insulator
• Observation of topological states residing at step edges of WTe2
• Imaging Quantum Spin Hall Edges in Monolayer WTe2
• Direct Visualization of 2D Topological Insulator in Single-layer 1T'-WTe2
• Evidence of Higher Order Topology in Multilayer WTe${}_2$ from Josephson Coupling through Anisotropic Hinge States
• Proximity-induced superconducting gap in the quantum spin Hall edge state of monolayer WTe${}_2$
• One-Dimensional Luttinger Liquids in a Two-Dimensional Moiré Lattice
• Quantum-Confined Electronic States arising from Moiré Pattern of MoS2-WSe2 Hetero-bilayers
• Flatbands and Mechanical Deformation Effects in the Moiré Superlattice of MoS${}_2$-WSe${}_2$ Heterobilayers
• Cooperative orbital moments and edge magnetoresistance in monolayer WTe${}_2$

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