Evidence of higher-order topology in multilayer WTe2 from Josephson coupling through anisotropic hinge states
Source abstract
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.
Source: europepmc · Quality: candidate unverified · Source record ↗
Research context
OpenAlex topics: Topological Materials and Phenomena · 2D Materials and Applications · Graphene research and applications
SciVX discovery tags are terminology-based. OpenAlex topics are source-provided classifications.
References (44)
Show source-provided references
1. Armitage, N. P., Mele, E. J. & Vishwanath, A. Weyl and Dirac semimetals in three-dimensional solids. Rev. Mod. Phys. 90, 015001 (2018).10.1103/RevModPhys.90.015001 ↗
2. Soluyanov, A. A. et al. Type-II Weyl semimetals. Nature 527, 495–498 (2015).10.1038/nature15768 ↗
3. Grushin, A. G. Consequences of a condensed matter realization of Lorentz-violating QED in Weyl semi-metals. Phys. Rev. D. 86, 045001 (2012).10.1103/PhysRevD.86.045001 ↗
4. Zyuzin, A. A. & Tiwari, R. P. Intrinsic anomalous Hall effect in type-II Weyl semimetals. JETP Lett. 103, 717–722 (2016).10.1134/S002136401611014X ↗
5. Ma, Q. et al. Observation of the nonlinear Hall effect under time-reversal-symmetric conditions. Nature 565, 337–342 (2019).10.1038/s41586-018-0807-6 ↗
6. Kang, K., Li, T., Sohn, E., Shan, J. & Mak, K. F. Nonlinear anomalous Hall effect in few-layer WTe2. Nat. Mater. 18, 324–328 (2019).10.1038/s41563-019-0294-7 ↗
7. O’Brien, T. E., Diez, M. & Beenakker, C. W. J. Magnetic breakdown and Klein tunneling in a type-II Weyl semimetal. Phys. Rev. Lett. 116, 236401 (2016).10.1103/PhysRevLett.116.236401 ↗
8. Yu, Z.-M., Yao, Y. & Yang, S. A. Predicted unusual magnetoresponse in type-II Weyl semimetals. Phys. Rev. Lett. 117, 077202 (2016).10.1103/PhysRevLett.117.077202 ↗
9. Chen, C.-Z. et al. Asymmetric Josephson effect in inversion symmetry breaking topological materials. Phys. Rev. B 98, 075430 (2018).10.1103/PhysRevB.98.075430 ↗
10. Pan, X.-C. et al. Pressure-driven dome-shaped superconductivity and electronic structural evolution in tungsten ditelluride. Nat. Commun. 6, 7805 (2015).
11. Qi, Y. et al. Superconductivity in Weyl semimetal candidate MoTe2. Nat. Commun. 7, 11038 (2016).
12. Deng, K. et al. Experimental observation of topological Fermi arcs in type-II Weyl semimetal MoTe2. Nat. Phys. 12, 1105–1110 (2016).10.1038/nphys3871 ↗
13. Sun, Y., Wu, S.-C., Ali, M. N., Felser, C. & Yan, B. Prediction of Weyl semimetal in orthorhombic MoTe2. Phys. Rev. B 92, 161107 (2015).10.1103/PhysRevB.92.161107 ↗
14. Qian, X., Liu, J., Fu, L. & Li, J. Quantum spin Hall effect in two-dimensional transition metal dichalcogenides. Science 346, 1344–1347 (2014).10.1126/science.1256815 ↗
15. Fei, Z. et al. Edge conduction in monolayer WTe2. Nat. Phys. 13, 677–682 (2017).10.1038/nphys4091 ↗
16. Wu, S. et al. Observation of the quantum spin Hall effect up to 100 Kelvin in a monolayer crystal. Science 359, 76–79 (2018).10.1126/science.aan6003 ↗
17. Tang, S. et al. Quantum spin Hall state in monolayer 1T’-WTe2. Nat. Phys. 13, 683–687 (2017).10.1038/nphys4174 ↗
18. Peng, L. et al. Observation of topological states residing at step edges of WTe2. Nat. Commun. 8, 659 (2017).
19. Cucchi, I. et al. Microfocus laser–angle-resolved photoemission on encapsulated mono-, bi-, and few-Layer 1T′-WTe2. Nano Lett. 19, 554–560 (2019).10.1021/acs.nanolett.8b04534 ↗
20. Wang, Z., Wieder, B. J., Li, J., Yan, B. & Bernevig, B. A. Higher-order topology, monopole nodal lines, and the origin of large Fermi arcs in transition metal dichalcogenides XTe2 (X=Mo, W). Phys. Rev. Lett. 123, 186401 (2019).10.1103/PhysRevLett.123.186401 ↗
21. runo, F. Y. et al.Observation of large topologically trivial Fermi arcs in the candidate type-II Weyl semimetal WTe2. Phys. Rev. B 94, (2016).10.1103/PhysRevB.94.121112 ↗
22. Zhang, W. et al. Quasiparticle interference of surface states in the type-II Weyl semimetal WTe2. Phys. Rev. B 96, 165125 (2017).10.1103/PhysRevB.96.165125 ↗
23. Ali, M. N. et al. Large, non-saturating magnetoresistance in WTe2. Nature 514, 205–208 (2014).10.1038/nature13763 ↗
24. Ali, M. N. et al. Correlation of crystal quality and extreme magnetoresistance of WTe2. Europhys. Lett. 110, 67002 (2015).10.1209/0295-5075/110/67002 ↗
25. Zhang, Y., Small, J. P., Pontius, W. V. & Kim, P. Fabrication and electric-field-dependent transport measurements of mesoscopic graphite devices. Appl. Phys. Lett. 86, 073104 (2005).10.1063/1.1862334 ↗
26. Zhu, Z. et al. Quantum oscillations, thermoelectric coefficients, and the Fermi surface of semimetallic WTe2. Phys. Rev. Lett. 114, 176601 (2015).10.1103/PhysRevLett.114.176601 ↗
27. Li, P. et al. Evidence for topological type-II Weyl semimetal WTe2. Nat. Commun. 8, 2150 (2017).
28. Lee, C.-H. et al. Tungsten ditelluride: a layered semimetal. Sci. Rep. 5, 10013 (2015).
29. Song, Q. et al. The in-plane anisotropy of WTe2 investigated by angle-dependent and polarized Raman spectroscopy. Sci. Rep. 6, 29254 (2016).
30. Courtois, H., Meschke, M., Peltonen, J. T. & Pekola, J. P. Origin of hysteresis in a proximity Josephson junction. Phys. Rev. Lett. 101, 067002 (2008).10.1103/PhysRevLett.101.067002 ↗
31. Hart, S. et al. Induced superconductivity in the quantum spin Hall edge. Nat. Phys. 10, 638–643 (2014).10.1038/nphys3036 ↗
32. Pribiag, V. S. et al. Edge-mode superconductivity in a two-dimensional topological insulator. Nat. Nanotechnol. 10, 593–597 (2015).10.1038/nnano.2015.86 ↗
33. Lee, J. H. et al. Local and nonlocal Fraunhofer-like pattern from an edge-stepped topological surface Josephson current distribution. Nano Lett. 14, 5029–5034 (2014).10.1021/nl501481b ↗
34. Schindler, F. et al. Higher-order topology in bismuth. Nat. Phys. 14, 918–924 (2018).10.1038/s41567-018-0224-7 ↗
35. Ezawa, M. Second-order topological insulators and loop-nodal semimetals in transition metal dichalcogenides XTe2 (X = Mo, W). Sci. Rep. 9, 5286 (2019).10.1038/s41598-019-41746-5 ↗
36. Gray, M. J. et al. Evidence for helical hinge zero modes in an Fe-based superconductor. Nano Lett. 19, 4890–4896 (2019).10.1021/acs.nanolett.9b00844 ↗
37. Bovenzi, N. et al. Chirality blockade of Andreev reflection in a magnetic Weyl semimetal. Phys. Rev. B 96, 035437 (2017).10.1103/PhysRevB.96.035437 ↗
38. Khanna, U., Kundu, A., Pradhan, S. & Rao, S. Proximity-induced superconductivity in Weyl semimetals. Phys. Rev. B 90, 195430 (2014).10.1103/PhysRevB.90.195430 ↗
39. Faraei, Z. & Jafari, S. A. Induced superconductivity in Fermi arcs. Phys. Rev. B 100, 035447 (2019).10.1103/PhysRevB.100.035447 ↗
40. Wang, W. et al. Evidence for an edge supercurrent in the Weyl superconductor MoTe2. Science 368, 534–537 (2020).10.1126/science.aaw9270 ↗
41. Huang, E. et al. Edge superconductivity in multilayer WTe2 Josephson junction. Natl Sci. Rev. https://doi.org/10.1093/nsr/nwaa114 (2020).10.1093/nsr/nwaa114 ↗
42. Kononov, A. et al. One-dimensional edge transport in few-layer WTe2. Nano Lett. 20, 4228–4233 (2020).10.1021/acs.nanolett.0c00658 ↗
43. Wu, Y. et al. Observation of Fermi arcs in the type-II Weyl semimetal candidate WTe2. Phys. Rev. B 94, 121113 (2016).10.1103/PhysRevB.94.121113 ↗
44. Tang, F., Po, H. C., Vishwanath, A. & Wan, X. Efficient topological materials discovery using symmetry indicators. Nat. Phys. 15, 470–476 (2019).10.1038/s41567-019-0418-7 ↗