Electrons in materials with linear dispersion behave as massless Weyl- or Dirac-quasiparticles, and continue to intrigue due to their close resemblance to elusive ultra-relativistic particles as well as their potential for future electronics. Yet the experimental signatures of Weyl-fermions are often subtle and indirect, in particular if they coexist with conventional, massive quasiparticles. Here we show a pronounced anomaly in the magnetic torque of the Weyl semimetal NbAs upon entering the quantum limit state in high magnetic fields. The torque changes sign in the quantum limit, signalling a reversal of the magnetic anisotropy that can be directly attributed to the topological nature of the Weyl electrons. Our results establish that anomalous quantum limit torque measurements provide a direct experimental method to identify and distinguish Weyl and Dirac systems.
Moll PJW, Potter AC, Nair NL, et al. Magnetic torque anomaly in the quantum limit of Weyl semimetals. Nature Communications. 2016;7. doi:10.1038/ncomms12492
Moll, P. J. W., Potter, A. C., Nair, N. L., Ramshaw, B. J., Modic, K. A., Riggs, S., … Analytis, J. G. (2016). Magnetic torque anomaly in the quantum limit of Weyl semimetals. Nature Communications. Springer Nature. https://doi.org/10.1038/ncomms12492
Moll, Philip J. W., Andrew C. Potter, Nityan L. Nair, B. J. Ramshaw, Kimberly A Modic, Scott Riggs, Bin Zeng, et al. “Magnetic Torque Anomaly in the Quantum Limit of Weyl Semimetals.” Nature Communications. Springer Nature, 2016. https://doi.org/10.1038/ncomms12492.
P. J. W. Moll et al., “Magnetic torque anomaly in the quantum limit of Weyl semimetals,” Nature Communications, vol. 7. Springer Nature, 2016.
Moll PJW, Potter AC, Nair NL, Ramshaw BJ, Modic KA, Riggs S, Zeng B, Ghimire NJ, Bauer ED, Kealhofer R, Ronning F, Analytis JG. 2016. Magnetic torque anomaly in the quantum limit of Weyl semimetals. Nature Communications. 7, 12492.
Moll, Philip J. W., et al. “Magnetic Torque Anomaly in the Quantum Limit of Weyl Semimetals.” Nature Communications, vol. 7, 12492, Springer Nature, 2016, doi:10.1038/ncomms12492.
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