# Evolution of the Fermi surface of Weyl semimetals in the transition metal pnictide family

## Abstract

Topological Weyl semimetals (TWSs) represent a novel state of topological quantum matter1,2,3,4 which not only possesses Weyl fermions (massless chiral particles that can be viewed as magnetic monopoles in momentum space) in the bulk and unique Fermi arcs generated by topological surface states, but also exhibits appealing physical properties such as extremely large magnetoresistance and ultra-high carrier mobility5,6,7,8. Here, by performing angle-resolved photoemission spectroscopy (ARPES) on NbP and TaP, we directly observed their band structures with characteristic Fermi arcs of TWSs. Furthermore, by systematically investigating NbP, TaP and TaAs from the same transition metal monopnictide family, we discovered their Fermiology evolution with spin–orbit coupling (SOC) strength. Our experimental findings not only reveal the mechanism to realize and fine-tune the electronic structures of TWSs, but also provide a rich material base for exploring many exotic physical phenomena (for example, chiral magnetic effects, negative magnetoresistance, and the quantum anomalous Hall effect) and novel future applications3,4,9,10,11.

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## Acknowledgements

Y.L.C. acknowledges support from the EPSRC (UK) grant EP/K04074X/1 and a DARPA (US) MESO project (no. N66001-11-1-4105). C.F. and B.Y. acknowledge financial support by the Deutsche Forschungsgemeinschaft DFG (Project No.EB 518/1-1 of DFG-SPP 1666 ‘Topological Insulators’) and by the ERC Advanced Grant (No. 291472 ‘Idea Heusler’). Advanced Light Source is operated by Department of Energy, Office of Basic Energy Science (contract DE-AC02-05CH11231).

## Author information

Authors

### Contributions

Y.L.C. conceived the experiments; Z.K.L. and L.X.Y. carried out ARPES measurements with the assistance of T.Z., H.P., H.F.Y., C.C., Y.Z. and S.-K.M.; D.P., M.S. and Y.F.G. synthesized and characterized the bulk single crystals; B.Y. and Y.S. performed ab initio calculations. All authors contributed to the scientific planning and discussions.

### Corresponding author

Correspondence to Y. L. Chen.

## Ethics declarations

### Competing interests

The authors declare no competing financial interests.

## Supplementary information

### Supplementary Information

Supplementary Information (PDF 2031 kb)

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Reprints and Permissions

Liu, Z., Yang, L., Sun, Y. et al. Evolution of the Fermi surface of Weyl semimetals in the transition metal pnictide family. Nature Mater 15, 27–31 (2016). https://doi.org/10.1038/nmat4457

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