Band Inversion in Topologically Nontrivial Half-Heusler Bismuthides: ²⁰⁹Bi NMR Study

Abstract

209Bi nuclear magnetic resonance (NMR) was measured in half-Heusler bismuthides ScPdBi, LuPdBi, and LuPtBi and discussed in conjunction with the NMR data recently reported for YPdBi and YPtBi. The observed 209Bi NMR spectra exhibit low intensity because of short nuclear transverse relaxation time (T2) governed by sizable structural disorder. Remarkably, the NMR frequency shifts are positive for topologically trivial ScPdBi and YPdBi, yet strongly negative for topologically nontrivial YPtBi, LuPtBi, and LuPdBi with postulated inversion of the electronic bands near the Fermi level. For the former two compounds, the spin–lattice relaxation rate (1/T1) is very large and seems correlated with the strength of spin–orbit coupling. The study demonstrates the capability of NMR spectroscopy to probe the band inversion in putative topological insulators.