Revealing temperature evolution of the Dirac band in ZrTe$_5$ via magneto-infrared spectroscopy

TL;DR

This study uses magneto-infrared spectroscopy to investigate how the Dirac band in ZrTe$_5$ evolves with temperature, revealing complex behavior that challenges previous assumptions about its topological phase transitions.

Contribution

It offers an alternative explanation for the temperature-dependent band gap evolution in ZrTe$_5$, considering conduction-valence band mixing and band inversion effects.

Findings

Band gap remains constant at low temperatures

Band gap increases at higher temperatures

Supports a strong topological insulator phase at low temperatures

Abstract

We report the temperature evolution of the Dirac band in semiconducting zirconium pentatelluride (ZrTe$_5$) using magneto-infrared spectroscopy. We find that the band gap is temperature independent at low temperatures and increases with temperature at elevated temperatures. Although such an observation seems to support a weak topological insulator phase at all temperatures and defy the previously reported topological phase transition (TPT) at an intermediate temperature in ZrTe$_5$, we show that it is also possible to explain the observation by considering the effect of conduction-valence band mixing and band inversion with a strong topological insulator phase at low temperatures. Our work provides an alternative picture of the band gap evolution across TPT.