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Evidence of higher-order topology in multilayer WTe2 from Josephson coupling through anisotropic hinge states

An Author Correction to this article was published on 17 July 2020

This article has been updated

Abstract

Td-WTe2 (non-centrosymmetric and orthorhombic), a type-II Weyl semimetal, is expected to have higher-order topological phases with topologically protected, helical one-dimensional hinge states when its Weyl points are annihilated. However, the detection of these hinge states is difficult due to the semimetallic behaviour of the bulk. In this study, we have spatially resolved the hinge states by analysing the magnetic field interference of the supercurrent in Nb–WTe2–Nb proximity Josephson junctions. The Josephson current along the a axis of the WTe2 crystal, but not along the b axis, showed a sharp enhancement at the edges of the junction, and the amount of enhanced Josephson current was comparable to the upper limits of a single one-dimensional helical channel. Our experimental observations suggest a higher-order topological phase in WTe2 and its corresponding anisotropic topological hinge states, in agreement with theoretical calculations. Our work paves the way for the study of hinge states in topological transition-metal dichalcogenides and analogous phases.

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Fig. 1: Anisotropy of the WTe2 crystal.
Fig. 2: Characteristics of the WTe2-based Josephson junction.
Fig. 3: Interference patterns of the WTe2 Josephson junction and extracted current profiles.
Fig. 4: Fraunhofer pattern of a partially insulated Josephson junction.

Data availability

The data that support the findings of this study are available from the corresponding authors on reasonable request.

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Acknowledgements

We thank H.-J. Lee and G.Y. Cho for critical reading of the manuscript. Y.-B.C. and G.-H.L. were supported by Samsung Science and Technology Foundation (project no. SSTF-BA1702-05) for device fabrications and low-temperature measurements, and the National Research Foundation of Korea (NRF) funded by the Korean Government (grant no. 2016R1A5A1008184) for data analysis. J.K. and S.-B.S. acknowledge the support from the National Research Foundation of Korea (grant no. 2017R1C1B2012729). B.J.K. acknowledges the support from the Institute for Basic Science (IBS-R014-A2). K.W. and T.T. acknowledge support from the Elemental Strategy Initiative conducted by MEXT, Japan and CREST (JPMJCR15F3), JST. K.C.F. acknowledges the support from the Army Research Office under Cooperative Agreement Number W911NF-17-1-0574. C.-Z.C. and K.T.L acknowledge the support of The Croucher Foundation and HKRGC (C6026-16W, 16324216, 16307117 and 16309718). M.N.A. acknowledges support from the Alexander von Humboldt Foundation’s Sofia Kovalevskaja Award and the BMBF MINERVA ARCHES Award.

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K.C.F., M.N.A., K.T.L. and G.-H.L. conceived and supervised the project. Y.-B.C. fabricated the samples. Y.-B.C. and J.P. performed transport experiments. J.Y. and M.N.A. provided the WTe2 crystal, and T.T. and K.W. provided the hexagonal boron nitride crystal. S.-B.S., B.J.K. and J.K. collected and analysed the polarized Raman spectrum. Y.X., C.-Z.C. and K.T.L. performed theoretical analysis and calculations. Y.-B.C., Y.X., K.C.F., M.N.A., K.T.L. and G.-H.L. wrote the paper with inputs from C.-Z.C., J.P., S.-B.S. and J.K.

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Correspondence to Kin Chung Fong, Mazhar N. Ali, Kam Tuen Law or Gil-Ho Lee.

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Supplementary Discussion Sections S1–S10, Figs. 1–10 and Tables 1 and 2.

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Choi, YB., Xie, Y., Chen, CZ. et al. Evidence of higher-order topology in multilayer WTe2 from Josephson coupling through anisotropic hinge states. Nat. Mater. 19, 974–979 (2020). https://doi.org/10.1038/s41563-020-0721-9

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