NMR and paramagnetic response of Dirac carriers in type-II semimetal NiTe₂

We used¹²⁵Te nuclear magnetic resonance to study the Dirac semimetals NiTe₂and NiTeSe, which feature type-II dispersion and Dirac nodes that are very close to the Fermi level. We find very large Knight shifts, which are dominated by the trivial electron states rather than those associated with the Dirac nodes. However, we also observe an anomalously large increased Knight shift at low temperatures with the field parallel to thecaxis in NiTe₂, perpendicular to the high mobility carriers. This is explained by a large paramagnetic shift proportional to the Van Vleck susceptibility, with the temperature dependence consistent with rearrangement of the density of states near the Dirac node due to Landau quantization. Density functional theory calculations of the orbital resolved bandstructure were performed to support this result. A lineshape splitting at lowTis also observed in NiTe₂which we show may be attributable to defect driven local variations in band ordering contributing to large differences in scattering rates for carriers close to the Dirac node.