NMR determination of Van Hove singularity and Lifshitz transitions in the nodal-line semimetal ZrSiTe

We have applied nuclear magnetic resonance spectroscopy to study the distinctive network of nodal lines in the Dirac semimetal ZrSiTe. The low-T behavior is dominated by a symmetry-protected nodal line, with NMR providing a sensitive probe of the diamagnetic response of the associated carriers. A sharp low-T minimum in the NMR shift and (T1T)-1 provides a quantitative measure of the dispersionless, quasi-two-dimensional behavior of this nodal line. We also identify a Van Hove singularity closely connected to this nodal line, and an associated T-induced Lifshitz transition. A disconnect in the NMR shift and linewidth at this temperature indicates the change in electronic behavior associated with this topological change. These features have an orientation-dependent behavior indicating a field-dependent scaling of the associated band energies.