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) WTe2. 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) WTe2. At the tBL edges, we observe the characteristic spectroscopic signatures of the QSH edge states. 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 WTe2and its topological edge states as a function of interlayer distance and conclude that it is possible to engineer the topology of WTe2bilayers via the twist angle as well as interlayer interactions.
| Original language | English |
|---|---|
| Pages (from-to) | 5674-5680 |
| Number of pages | 7 |
| Journal | Nano Letters |
| Volume | 22 |
| Issue number | 14 |
| DOIs | |
| State | Published - Jul 27 2022 |
Funding
We acknowledge helpful discussions with Justin Song. P.G. would like to acknowledge fruitful discussions with Jaron T. Krogel and Yubo “Paul” Yang. B.M.H. was supported by the Department of Energy under the Early Career award program (#DE-SC0018115) for design of the experiments and writing of the manuscript. F.L. and D.W. were supported by the NSF DMR-1809145 for the STM measurements. The authors gratefully acknowledge NSF DMR-1626099 for acquisition of the STM instrument. F.L. was supported by the Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, which is a DOE Office of Science User Facility. F.L. acknowledges funding from the Alexander von Humboldt foundation through a Feodor Lynen postdoctoral fellowship. F.L. further acknowledges funding by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) within the Priority Programme SPP 2244 (project no. 443416235) and the Bavarian Ministry of Economic Affairs, Regional Development and Energy within Bavaria’s High-Tech Agenda Project “Bausteine für das Quantencomputing auf Basis topologischer Materialien mit experimentellen und theoretischen Ansätzen”. The authors thank the Pennsylvania State University Two-Dimensional Crystal Consortium - Materials Innovation Platform (2DCC-MIP), which is supported by NSF DMR-1539916 for supplying further 2D materials. While support for initial work by A.D.P. and P.G. was by the Oak Ridge National Laboratory’s Laboratory Directed Research and Development project (Project ID 7448, PI: P.G.) work on the key final results presented in the manuscript was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division, as part of the Computational Materials Sciences Program and Center for Predictive Simulation of Functional Materials. Computations were performed on the Compute and Data Environment for Science (CADES) cluster at the Oak Ridge National Laboratory, which is supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC05-00OR22725 at the Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, which is a DOE Office of Science User Facility. Crystal growth and characterization at ORNL was supported by the US Department of Energy, Office of Science, Basic Energy Sciences, Division of Materials Sciences and Engineering. We acknowledge helpful discussions with Justin Song. P.G. would like to acknowledge fruitful discussions with Jaron T. Krogel and Yubo “Paul” Yang. B.M.H. was supported by the Department of Energy under the Early Career award program (#DE-SC0018115). F.L. and D.W. were supported by the NSF DMR-1809145 for the STM measurements. The authors gratefully acknowledge NSF DMR-1626099 for acquisition of the STM instrument. F.L. was supported by the Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, which is a DOE Office of Science User Facility. F.L. acknowledges funding from the Alexander von Humboldt foundation through a Feodor Lynen postdoctoral fellowship. F.L. further acknowledges funding by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) within the Priority Programme SPP 2244 (project no. 443416235) and the Bavarian Ministry of Economic Affairs, Regional Development and Energy within Bavaria’s High-Tech Agenda Project “Bausteine für das Quantencomputing auf Basis topologischer Materialien mit experimentellen und theoretischen Ansätzen”. The authors thank the Pennsylvania State University Two-Dimensional Crystal Consortium - Materials Innovation Platform (2DCC-MIP), which is supported by NSF DMR-1539916 for supplying further 2D materials. While support for initial work by A.D.P. and P.G. was by the Oak Ridge National Laboratory’s Laboratory Directed Research and Development project (Project ID 7448, PI: P.G.), work on the key final results presented in the manuscript was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division, as part of the Computational Materials Sciences Program and Center for Predictive Simulation of Functional Materials. Computations were performed on the Compute and Data Environment for Science (CADES) cluster at the Oak Ridge National Laboratory, which is supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC05-00OR22725, at the Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, which is a DOE Office of Science User Facility. Crystal growth and characterization at ORNL was supported by the US Department of Energy, Office of Science, Basic Energy Sciences, Division of Materials Sciences and Engineering.
| Funders | Funder number |
|---|---|
| CADES | DE-AC05-00OR22725 |
| Center for Nanophase Materials Sciences | |
| Data Environment for Science | |
| Oak Ridge National Laboratory | ID 7448 |
| National Science Foundation | DMR-1626099, DMR-1809145 |
| U.S. Department of Energy | -SC0018115 |
| Alexander von Humboldt-Stiftung | |
| Office of Science | |
| Basic Energy Sciences | |
| Oak Ridge National Laboratory | |
| Pennsylvania State University | DMR-1539916 |
| Division of Materials Sciences and Engineering | |
| Deutsche Forschungsgemeinschaft | 443416235 |
| Bayerisches Staatsministerium für Wirtschaft, Infrastruktur, Verkehr und Technologie |
Keywords
- Topological insulators
- quantum spin Hall edge states
- scanning tunneling microscopy
- twisted bilayers
- van der Waals heterostructure