Site-dependent Local Spin Susceptibility and Low-energy Excitation in a Weyl Semimetal WTe$_2$

Abstract

Site-dependent local spin susceptibility is investigated with 125 Te nuclear magnetic resonance in a Weyl semimetal WTe 2 . The nuclear spin-lattice relaxation rate 1/T 1 T shows a dependence of the square of temperature T at high temperatures, followed by a constant behavior below 50 K. The temperature dependence features Weyl fermions appearing around the linearly crossing bands. The Knight shift K scales to the square root of 1/T 1 T , corroborating a predominant spin contribution in low-lying excitation. The observed dependence of K and 1/T 1 T on the four Te sites shows the site-dependent electron correlation and density of states. The angular profile of the NMR spectrum gives the anisotropic hyperfine coupling tensor, consistent with 5p hole occupations on Te sites.