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arXiv · 2111.06182

Weyl Fermion Magneto-Electrodynamics and Ultra-low Field Quantum Limit in TaAs

Zhengguang Lu·Patrick Hollister·Mykhaylo Ozerov·Seongphill Moon·Eric D. Bauer·Filip Ronning·Dmitry Smirnov·Long Ju·B. J. Ramshaw
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Abstract

Topological semimetals are predicted to exhibit unconventional electrodynamics, but a central experimental challenge is singling out the contributions from the topological bands. TaAs is the prototypical example, where 24 Weyl points and 8 trivial Fermi surfaces make the interpretation of any experiment in terms of band topology ambiguous. We report magneto-infrared reflection spectroscopy measurements on TaAs. We observed sharp inter-Landau level transitions from a single pocket of Weyl Fermions in magnetic fields as low as 0.4 tesla. We determine the W2 Weyl point to be 8.3 meV below the Fermi energy, corresponding to a quantum limit - the field required to reach the lowest LL - of 0.8 Tesla - unprecedentedly low for Weyl Fermions. LL spectroscopy allows us to isolate these Weyl Fermions from all other carriers in TaAs and our result provides a new way for directly exploring the more exotic quantum phenomena in Weyl semimetals, such as the chiral anomaly.

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Zhengguang Lu, Patrick Hollister, Mykhaylo Ozerov, Seongphill Moon, Eric D. Bauer, Filip Ronning, Dmitry Smirnov, Long Ju, B. J. Ramshaw. 2021-11-11. Weyl Fermion Magneto-Electrodynamics and Ultra-low Field Quantum Limit in TaAs. https://arxiv.org/abs/2111.06182

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