Double Quantum Spin Hall Phase in Moiré WSe<sub>2</sub>.
basic_science · Level V
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- Record sourced from PubMed, PMID 39506321.
- Also identified by DOI 10.1021/acs.nanolett.4c05308.
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Abstract
Quantum spin Hall (QSH) insulators are topologically protected phases of matter in two dimensions that can support a pair of helical edge states surrounding an insulating bulk. A higher (even) number of helical edge state pairs is usually not possible in real materials because spin mixing would gap out the edge states. Here, we report experimental evidence for a QSH phase with one and two pairs of helical edge states in twisted bilayer WSe<sub>2</sub> at Moiré hole filling factor ν = 2 and 4, respectively. We observe nearly quantized (within 10%) resistance plateaus of <math xmlns="http://www.w3.org/1998/Math/MathML"><mfrac><mrow><mi>h</mi></mrow><mrow><mi>ν</mi><msup><mrow><mi>e</mi></mrow><mrow><mn>2</mn></mrow></msup></mrow></mfrac></math> and large nonlocal transport at ν = 2 and 4 while the bulk is insulating. The resistance is independent of the out-of-plane magnetic field and increases under an in-plane magnetic field. The results agree with quantum transport of helical edge states in a material with high spin Chern bands protected by Ising spin conservation symmetry.