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Disorder-induced multifractal superconductivity in monolayer niobium dichalcogenides

Nature Physics volume 15, pages 904–910 (2019)Cite this article

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Abstract

The interplay between disorder and superconductivity is a subtle and fascinating phenomenon in quantum many-body physics. Conventional superconductors are insensitive to dilute non-magnetic impurities, known as Anderson’s theorem1. Destruction of superconductivity and even superconductor–insulator transitions2,3,4,5,6,7,8,9,10 occur in the regime of strong disorder. Hence, disorder-enhanced superconductivity is rare and has been observed only in some alloys or granular states11,12,13,14,15,16,17. Owing to the entanglement of various effects, the mechanism of enhancement is still under debate. Here, we report a well-controlled disorder effect in the recently discovered monolayer NbSe2 superconductor. The superconducting transition temperatures of NbSe2 monolayers are substantially increased by disorder. Realistic theoretical modelling shows that the unusual enhancement possibly arises from the multifractality18,19 of electron wavefunctions. This work provides experimental evidence of the multifractal superconducting state.

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Fig. 1: Epitaxial NbSe2 monolayer.
Fig. 2: Disorder-enhanced superconductivity.
Fig. 3: Theoretical modelling.
Fig. 4: Spatially resolved spectra near the Fermi level.

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All relevant data are available from the corresponding authors on reasonable request.

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Acknowledgements

We thank A. M. García-García for stimulating discussions. This work is supported by the Ministry of Science and Technology of China (grant nos. 2018YFA0305600, 2016YFA0301002, 2017YFA0303302, 2013CB934600), the National Natural Science Foundation of China (grant nos. 51561145005, 11622433, 11574175, 51522212, 11774008, 11704414). K.T.L. would like to acknowledge the support of HKRGC (grants 16324216, 16309718, 6307117 and C6026-16W), Croucher Foundation and Dr. Tai-Chin Lo Foundation. L.G. is partially supported by Strategic Priority Research Program of the Chinese Academy of Sciences (grant no. XDB07030200). M.S.B. and N.N. gratefully acknowledge support from the CREST, JST (no. JPMJCR16F1). N.N. is also supported by JSPS KAKENHI grant numbers 18H03676 and 26103006. M.S.B. is also supported by the Japan Society for Promotion of Science (Grant-in-Aid for Scientific Research (S) no. 24224009).

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  1. These authors contributed equally: Kun Zhao, Haicheng Lin, Xiao Xiao.

Authors and Affiliations

  1. State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing, China

    Kun Zhao, Haicheng Lin, Wantong Huang, Wei Yao, Mingzhe Yan, Zi-Xiang Li, Shuyun Zhou, Hong Yao, Qi-Kun Xue, Xi Chen & Shuai-Hua Ji

  2. Department of Physics, Hong Kong University of Science and Technology, Hong Kong, China

    Xiao Xiao & Kam Tuen Law

  3. International Center for Quantum Materials, School of Physics, Peking University, Beijing, China

    Ying Xing & Jian Wang

  4. Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, China

    Qinghua Zhang & Lin Gu

  5. Institute for Advanced Study, Tsinghua University, Beijing, China

    Zi-Xiang Li & Hong Yao

  6. RIKEN Center for Emergent Matter Science, Wako, Japan

    Shintaro Hoshino, Mohammad Saeed Bahramy, Naoto Nagaosa & Shuai-Hua Ji

  7. Department of Applied Physics, University of Tokyo, Tokyo, Japan

    Mohammad Saeed Bahramy & Naoto Nagaosa

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Contributions

S.-H.J. and X.C. coordinated the project and designed the experiments. K.Z., H.L. and W.H. performed the molecular beam epitaxy growth and STM experiments. X.X. and K.T.L. provided the multifractal interpretation and the model calculations. W.Y., M.Y. and S.Z. contributed the ARPES measurement. Q.Z. and L.G. contributed the STEM characterization. M.S.B. calculated the electronic band by density functional theory. Z.-X.L., S.H., H.Y. and N.N. contributed part of the theoretical analysis. K.Z., H.L., X.X., K.T.L., S.-H.J. and X.C. co-wrote the paper. All authors discussed the results and commented on the manuscript.

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Correspondence to Xi Chen or Shuai-Hua Ji.

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Zhao, K., Lin, H., Xiao, X. et al. Disorder-induced multifractal superconductivity in monolayer niobium dichalcogenides. Nat. Phys. 15, 904–910 (2019). https://doi.org/10.1038/s41567-019-0570-0

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