title: Magnetic torque anomaly in the quantum limit of Weyl semimetals.
abstract: 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.
authors.affiliation: Department of Physics, University of California Berkeley, 359 Birge Hall, Berkeley, California 94720, USA.|Max-Planck-Institute for Chemical Physics of Solids, Nöthnitzer Strasse 40, Dresden 01187, Germany.
authors.forename: Philip J W
authors.initials: PJ
authors.lastname: Moll
authors.affiliation: Department of Physics, University of California Berkeley, 359 Birge Hall, Berkeley, California 94720, USA.
authors.forename: Andrew C
authors.initials: AC
authors.lastname: Potter
authors.affiliation: Department of Physics, University of California Berkeley, 359 Birge Hall, Berkeley, California 94720, USA.
authors.forename: Nityan L
authors.initials: NL
authors.lastname: Nair
authors.affiliation: National High Magnetic Field Laboratory, TA-35, Los Alamos, New Mexico 87545, USA.
authors.forename: B J
authors.initials: BJ
authors.lastname: Ramshaw
authors.affiliation: Max-Planck-Institute for Chemical Physics of Solids, Nöthnitzer Strasse 40, Dresden 01187, Germany.|National High Magnetic Field Laboratory, TA-35, Los Alamos, New Mexico 87545, USA.
authors.forename: K A
authors.initials: KA
authors.lastname: Modic
authors.affiliation: National High Magnetic Field Laboratory, 1800 E. Paul Dirac Dr., Tallahassee, Florida 32310, USA.
authors.forename: Scott
authors.initials: S
authors.lastname: Riggs
authors.affiliation: National High Magnetic Field Laboratory, 1800 E. Paul Dirac Dr., Tallahassee, Florida 32310, USA.
authors.forename: Bin
authors.identifier: 0000-0002-0090-4371
authors.initials: B
authors.lastname: Zeng
authors.affiliation: Los Alamos National Laboratory, TA-3, Los Alamos, New Mexico 87545, USA.
authors.forename: Nirmal J
authors.initials: NJ
authors.lastname: Ghimire
authors.affiliation: Los Alamos National Laboratory, TA-3, Los Alamos, New Mexico 87545, USA.
authors.forename: Eric D
authors.initials: ED
authors.lastname: Bauer
authors.affiliation: Department of Physics, University of California Berkeley, 359 Birge Hall, Berkeley, California 94720, USA.
authors.forename: Robert
authors.initials: R
authors.lastname: Kealhofer
authors.affiliation: Los Alamos National Laboratory, TA-3, Los Alamos, New Mexico 87545, USA.
authors.forename: Filip
authors.initials: F
authors.lastname: Ronning
authors.affiliation: Department of Physics, University of California Berkeley, 359 Birge Hall, Berkeley, California 94720, USA.
authors.forename: James G
authors.initials: JG
authors.lastname: Analytis