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# Ultrahigh conductivity in Weyl semimetal NbAs nanobelts

## Abstract

In two-dimensional (2D) systems, high mobility is typically achieved in low-carrier-density semiconductors and semimetals. Here, we discover that the nanobelts of Weyl semimetal NbAs maintain a high mobility even in the presence of a high sheet carrier density. We develop a growth scheme to synthesize single crystalline NbAs nanobelts with tunable Fermi levels. Owing to a large surface-to-bulk ratio, we argue that a 2D surface state gives rise to the high sheet carrier density, even though the bulk Fermi level is located near the Weyl nodes. A surface sheet conductance up to 5–100 S per □ is realized, exceeding that of conventional 2D electron gases, quasi-2D metal films, and topological insulator surface states. Corroborated by theory, we attribute the origin of the ultrahigh conductance to the disorder-tolerant Fermi arcs. The evidenced low-dissipation property of Fermi arcs has implications for both fundamental study and potential electronic applications.

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## Data availability

The data that support the plots within this paper and other findings of this study are available from the corresponding author upon reasonable request.

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## Acknowledgements

F.X. was supported by National Natural Science Foundation of China (grant nos. 61322407, 11474058, 61674040 and 11874116), National Key Research and Development Program of China (grant nos. 2017YFA0303302 and 2018YFA0305601) and the National Young 1000 Talent Plan. Part of the sample fabrication was performed at Fudan Nano-fabrication Laboratory. Part of the transport measurements was performed at the High Magnetic Field Laboratory, CAS. A portion of this work was performed at the National High Magnetic Field Laboratory (USA), which is supported by the National Science Foundation (NSF) cooperative agreement no. DMR-1644779, no. DMR-1157490 and the State of Florida. S.Y.S. was supported by NSF DMR (grant no. 1411336). Australian Research Council and Australian Microscopy and Microanalysis Research Facility are acknowledged for supporting the nano-characterization. A.N. acknowledges support from ETH Zurich. S.S. acknowledges support from Science Foundation Ireland (14/IA/2624 and 16/US-C2C/3287). Part of the computations were carried out at the Trinity Centre for High-Performance Computing. J.Z. was supported by Youth Innovation Promotion Association CAS (grant no. 2018486), the Innovative Program of Development Foundation of Hefei Center for Physical Science and Technology (grant no. 2017FXCX001), and the Scientific Instrument Developing Project of the Chinese Academy of Sciences (grant no.YJKYYQ20180059). C.Z. and X.Y. were supported by China Scholarships Council (CSC) (grant nos. 201706100053 and 201706100054). F.X. acknowledges the tremendous help from Y. Chen for TEM characterization in Beijing University of Technology. C.Z. thanks Y. Ding for insightful discussions.

## Author information

Authors

### Contributions

F.X. conceived the ideas and supervised the overall research. Z.N. synthesized NbAs nanobelts with help from C.Z., T.G., H.Z. and X.Z. C.Z. and Z.N. fabricated the devices. C.Z., X.Y. and Y.L. carried out the transport measurements assisted by J.Z. and L.P. X.Y., Y.Z., Z.L., X.H. and J.Z. performed the sample characterization. C.Z. analysed the transport data. Y.D., X.W., A.N., S.S. and S.Y.S. provided the theoretical support. C.Z., S.Y.S. and F.X. wrote the paper with help from all other co-authors.

### Corresponding author

Correspondence to Faxian Xiu.

## Ethics declarations

### Competing interests

The authors declare no competing interests.

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## Supplementary information

### Supplementary Information

Supplementary Notes 1–6, Supplementary Figures 1–8, Supplementary Table 1, Supplementary References 1–26

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Zhang, C., Ni, Z., Zhang, J. et al. Ultrahigh conductivity in Weyl semimetal NbAs nanobelts. Nat. Mater. 18, 482–488 (2019). https://doi.org/10.1038/s41563-019-0320-9

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• ### Cycling Fermi arc electrons with Weyl orbits

• Cheng Zhang
• Yi Zhang
• Faxian Xiu

Nature Reviews Physics (2021)