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Evidence of topological boundary modes with topological nodal-point superconductivity

Nature Physics volume 17, pages 1413–1419 (2021)Cite this article

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Abstract

Topological superconductors are an essential component for topologically protected quantum computation and information processing. Although signatures of topological superconductivity have been reported in heterostructures, material realizations of intrinsic topological superconductors are rather rare. Here we use scanning tunnelling spectroscopy to study the transition metal dichalcogenide 4Hb-TaS2 that interleaves superconducting 1H-TaS2 layers with strongly correlated 1T-TaS2 layers, and find spectroscopic evidence for the existence of topological surface superconductivity. These include edge modes running along the 1H-layer terminations as well as under the 1T-layer terminations, where they separate between superconducting regions of distinct topological nature. We also observe signatures of zero-bias states in vortex cores. All the boundary modes exhibit crystallographic anisotropy, which—together with a finite in-gap density of states throughout the 1H layers—allude to the presence of a topological nodal-point superconducting state. Our theoretical modelling attributes this phenomenology to an inter-orbital pairing channel that necessitates the combination of surface mirror symmetry breaking and strong interactions. It, thus, suggests a topological superconducting state realized in a natural compound.

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Fig. 1: CDW, superconductivity and ZBC peaks in vortex cores.
Fig. 2: Spectroscopic mapping of the dispersing edge mode on 1H step edges.
Fig. 3: Spectroscopic mapping of the anisotropic edge mode below 1T step edges.
Fig. 4: Topological nodal superconductivity induced by inter-orbital pairing.

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Data availability

The data needed to reproduce the main text figures are available on Zenodo (https://doi.org/10.5281/zenodo.5229526).

Code availability

The codes used in theoretical simulations and calculations are available from the corresponding authors upon reasonable request.

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Acknowledgements

N.A., H.B. and B.Y acknowledge the German-Israeli Foundation for Scientific Research and Development (GIF grant no. I-1364-303.7/2016). H.B. and N.A. acknowledge the European Research Council (ERC, project no. TOPO NW). B.Y. acknowledges financial support by the European Research Council (ERC Consolidator Grant, no. 815869), the Israel Science Foundation (ISF nos. 1251/19, 3520/20 and 2932/21) and the Willner Family Leadership Institute for the Weizmann Institute of Science, the Benoziyo Endowment Fund for the Advancement of Science, the Ruth and Herman Albert Scholars Program for New Scientists, and the Israel Science Foundation (ISF 1251/19). G.A.F. gratefully acknowledges partial support from the National Science Foundation through NSF grant nos. DMR-1720595 and DMR-1949701. Y.O. acknowledges partial support through the ERC under the European Union’s Horizon 2020 research and innovation programme (grant agreement LEGOTOP no. 788715), the ISF Quantum Science and Technology (2074/19), the BSF and NSF (2018643), and the CRC/Transregio 183. A.K. acknowledges the Israel Science Foundation (ISF 320/17).

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Author notes

  1. These authors contributed equally: Abhay Kumar Nayak, Aviram Steinbok, Yotam Roet.

Authors and Affiliations

  1. Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, Israel

    Abhay Kumar Nayak, Aviram Steinbok, Yotam Roet, Jahyun Koo, Gilad Margalit, Binghai Yan, Yuval Oreg, Nurit Avraham & Haim Beidenkopf

  2. Department of Physics, Technion–Israel Institute of Technology, Haifa, Israel

    Irena Feldman, Avior Almoalem & Amit Kanigel

  3. Department of Physics, Northeastern University, Boston, MA, USA

    Gregory A. Fiete

  4. Department of Physics, Massachusetts Institute of Technology, Cambridge, MA, USA

    Gregory A. Fiete

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Contributions

A.K.N., A.S. and Y.R. acquired and analysed the data. A.K., N.A. and H.B. conceived the experiments. J.K. and B.Y. calculated the ab initio model. G.M., G.A.F., B.Y. and Y.O. calculated the theoretical model. I.F., A.A. and A.K. grew the material. A.K.N., N.A. and H.B. wrote the manuscript with substantial contributions from all the authors.

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Correspondence to Nurit Avraham or Haim Beidenkopf.

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Nayak, A.K., Steinbok, A., Roet, Y. et al. Evidence of topological boundary modes with topological nodal-point superconductivity. Nat. Phys. 17, 1413–1419 (2021). https://doi.org/10.1038/s41567-021-01376-z

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