1Institute of Physics and Beijing National Laboratory for Condensed Matter Physics, Chinese Academy of Sciences, Beijing 100190 2Collaborative Innovation Center of Quantum Matter, Beijing 100190 3School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190
Abstract：There is a long-standing confusion concerning the physical origin of the anomalous resistivity peak in transition metal pentatelluride HfTe$_{5}$. Several mechanisms, such as the formation of charge density wave or polaron, have been proposed, but so far no conclusive evidence has been presented. In this work, we investigate the unusual temperature dependence of magneto-transport properties in HfTe$_{5}$. It is found that a three-dimensional topological Dirac semimetal state emerges only at around $T_{\rm p}$ (at which the resistivity shows a pronounced peak), as manifested by a large negative magnetoresistance. This accidental Dirac semimetal state mediates the topological quantum phase transition between the two distinct weak and strong topological insulator phases in HfTe$_{5}$. Our work not only provides the first evidence of a temperature-induced critical topological phase transition in HfTe$_{5}$ but also gives a reasonable explanation on the long-lasting question.
2017, Vol. 34 
