Emergent Weyl fermion excitations in TaP explored by 181Ta quadrupole resonance

H. Yasuoka, T. Kubo, Y. Kishimoto, D. Kasinathan, M. Schmidt, B. Yan, Y. Zhang, H. Tou, C. Felser, A. P. Mackenzie, M. Baenitz

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31 Citations (Scopus)


The 181Ta quadrupole resonance [nuclear quadrupole resonance (NQR)] technique is utilized to investigate the microscopic magnetic properties of the Weyl semimetal TaP. We find three zero-field NQR signals associated with the transition between the quadrupole split levels for Ta with I=7/2 nuclear spin. A quadrupole coupling constant, νQ=19.250 MHz, and an asymmetric parameter of the electric field gradient, η=0.423, are extracted, in good agreement with band structure calculations. In order to examine the magnetic excitations, the temperature dependence of the spin-lattice relaxation rate (1/T1T) is measured for the f2 line (±5/2↔±3/2 transition). We find that there exist two regimes with quite different relaxation processes. Above T≈30 K, a pronounced (1/T1T) α T2 behavior is found, which is attributed to the magnetic excitations at the Weyl nodes with temperature-dependent orbital hyperfine coupling. Below T, the relaxation is mainly governed by a Korringa process with 1/T1T=const, accompanied by an additional T-1/2-type dependence to fit our experimental data. We show that Ta NQR is a novel probe for the bulk Weyl fermions and their excitations.

Original languageEnglish
Article number236403
Number of pages6
JournalPhysical Review Letters
Issue number23
Publication statusPublished - 9 Jun 2017


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