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# Landau quantization and quasiparticle interference in the three-dimensional Dirac semimetal Cd3As2

## Abstract

Condensed-matter systems provide a rich setting to realize Dirac1 and Majorana2 fermionic excitations as well as the possibility to manipulate them for potential applications3,4. It has recently been proposed that chiral, massless particles known as Weyl fermions can emerge in certain bulk materials5,6 or in topological insulator multilayers7 and give rise to unusual transport properties, such as charge pumping driven by a chiral anomaly8. A pair of Weyl fermions protected by crystalline symmetry effectively forming a massless Dirac fermion has been predicted to appear as low-energy excitations in a number of materials termed three-dimensional Dirac semimetals9,10,11. Here we report scanning tunnelling microscopy measurements at sub-kelvin temperatures and high magnetic fields on the II–V semiconductor Cd3As2. We probe this system down to atomic length scales, and show that defects mostly influence the valence band, consistent with the observation of ultrahigh-mobility carriers in the conduction band. By combining Landau level spectroscopy and quasiparticle interference, we distinguish a large spin-splitting of the conduction band in a magnetic field and its extended Dirac-like dispersion above the expected regime. A model band structure consistent with our experimental findings suggests that for a magnetic field applied along the axis of the Dirac points, Weyl fermions are the low-energy excitations in Cd3As2.

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## Acknowledgements

The work at Princeton and the Princeton Nanoscale Microscopy Laboratory was supported by the ARO MURI programme W911NF-12-1-0461, DARPA-SPWAR Meso programme N6601-11-1-4110, NSF-DMR1104612, ONR- N00014-11-1-0635, and NSF-MRSEC NSF-DMR0819860 programmes.

## Author information

Authors

### Contributions

S.J. and B.B.Z. performed STM experiments with assistance from A.G. Theoretical simulations were constructed by I.K., A.C.P. and A.V. Q.D.G. and R.J.C. synthesized the materials. S.J. and B.B.Z. performed analysis and modelling. The manuscript was written by S.J., B.B.Z., B.E.F. and A.Y. All authors commented on the manuscript.

### Corresponding author

Correspondence to Ali Yazdani.

## Ethics declarations

### Competing interests

The authors declare no competing financial interests.

## Supplementary information

### Supplementary Information

Supplementary Information (PDF 1463 kb)

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Jeon, S., Zhou, B., Gyenis, A. et al. Landau quantization and quasiparticle interference in the three-dimensional Dirac semimetal Cd3As2. Nature Mater 13, 851–856 (2014). https://doi.org/10.1038/nmat4023

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