Speaker
Description
We present an infrared spectroscopy study of ZrTe$_5$, which realizes a recent theoretical proposal that this material exhibits a temperature-driven topological quantum phase transition from a weak to a strong topological insulating state through an intermediate Dirac semimetal state around $T_p \simeq$ 138K. Our study details the temperature evolution of the energy gap in the bulk electronic structure. We found that the energy gap closes around $T_p$ where the optical response exhibits characteristic signature of a Dirac semimetal state. A comparison with previous studies suggests that the divergent results and conclusions about the topological nature of ZrTe$_5$ can be reconciled by a variation of $T_p$, depending on the crystal growth conditions.
