Unraveling the topology of ZrTe$_5$ by changing temperature

TL;DR

This study investigates how temperature influences the topological phase of ZrTe$_5$, revealing that thermal effects can switch its topological classification and proposing a temperature-based method for phase identification.

Contribution

The paper demonstrates that temperature-dependent band gap behavior can reliably distinguish between strong and weak topological insulator phases in ZrTe$_5$, offering a new diagnostic approach.

Findings

Band gap sensitivity to temperature varies with topological phase.

Electron-phonon interactions significantly affect temperature dependence.

Temperature trend of band gap indicates topological nature.

Abstract

We study the effects of temperature on the topological nature of ZrTe$_5$, which sits near the phase boundary between strong and weak topological insulating orders. Using first-principles calculations, we show that the band gap and the topological indices of ZrTe$_5$ are extremely sensitive to thermal expansion, and that the electron-phonon interaction accounts for more than a third of the total temperature-dependent effects in ZrTe$_5$. We find that the temperature dependence of the band gap has an opposite sign in the strong and weak topological insulator phases. Based on this insight, we propose a robust and unambiguous method to determine the topological nature of any given sample of ZrTe$_5$: if the band gap decreases with temperature it is a strong topological insulator, and if it increases with temperature it is a weak topological insulator. An analogous strategy is expected to be generally applicable to other materials and to become particularly important in the vicinity of topological phase boundaries where other methods provide ambiguous results.