NMR study of topological chalcogenide ZrTe₅

In this work, we describe the results of ¹²⁵Te NMR measurements vs crystal orientation on an aligned-crystal sample of the topological chalcogenide ZrTe₅. Results measured with B along the a crystal axis indicate a Lifshitz transition with the chemical potential crossing a gapped Dirac node. With a magnetic field of B = 9T parallel to the b axis we probe the quantum-limit behavior of the Dirac-type carriers very close to E_F. In this orientation, with T decreasing toward the Lifshitz transition, we observe an abrupt reduction in spin-lattice relaxation rate, indicating appearance of a gapped or very low-carrier phase in the n-type region. At lower temperatures, we find a further change, with a large decrease in shift for the zigzag Te site commencing at 60 K. This change is consistent with the appearance of a spin-polarized state at low temperatures. These transformations are also consistent with a recently reported B-T phase diagram [1], and we discuss the nature of these phases based on the NMR results.

[1] Tang et al., Nature 569, 537 (2019).