Large quantum-spin-Hall gap in single-layer 1T' WSe<sub>2</sub>.
basic_science · Level V
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- Record sourced from PubMed, PMID 29784909.
- Also identified by DOI 10.1038/s41467-018-04395-2 and PMC identifier 5962594.
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Abstract
Two-dimensional (2D) topological insulators (TIs) are promising platforms for low-dissipation spintronic devices based on the quantum-spin-Hall (QSH) effect, but experimental realization of such systems with a large band gap suitable for room-temperature applications has proven difficult. Here, we report the successful growth on bilayer graphene of a quasi-freestanding WSe<sub>2</sub> single layer with the 1T' structure that does not exist in the bulk form of WSe<sub>2</sub>. Using angle-resolved photoemission spectroscopy (ARPES) and scanning tunneling microscopy/spectroscopy (STM/STS), we observe a gap of 129 meV in the 1T' layer and an in-gap edge state located near the layer boundary. The system's 2D TI characters are confirmed by first-principles calculations. The observed gap diminishes with doping by Rb adsorption, ultimately leading to an insulator-semimetal transition. The discovery of this large-gap 2D TI with a tunable band gap opens up opportunities for developing advanced nanoscale systems and quantum devices.