| 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_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. |
