NMR investigation of topological quantum material ZrTe₅

In this work, we performed ¹²⁵Te NMR measurements on the topological quantum material ZrTe₅. The measured spin-lattice relaxation rates (1/T₁) can be well-explained by a theoretical model for Dirac electron systems, which reveals that the topological characteristic of ZrTe₅ is T-dependent. Combined with DFT calculations, the topological transition ordering can be confirmed from weak topological state to strong topological state with temperature increasing, the reverse of what has been proposed. The T-dependence of Dirac band gap can be derived from NMR results, demonstrating a gapless Dirac semimetal state occurring at a Lifshitz transition temperature, T_c = 85 K in our crystals. We also show that the changes in NMR shift at the Lifshitz transition provide direct evidence of band inversion when the topological phase transition occurs.