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.
Highlights
Topological insulators (TIs) and semimetals have become an important field of condensed matter over the past decade
We propose that monitoring the temperature dependence of the band gap provides an unambiguous way to determine the topological nature of any given sample of ZrTe5, which may be more generally applicable to materials close to topological phase boundaries
We find that, starting from small volumes, the band gap decreases with increasing volume in the strong TI phase
Summary
Topological insulators (TIs) and semimetals have become an important field of condensed matter over the past decade. An intriguing addition to the family of topological matter was made by Weng and coauthors, who proposed monolayers of transition-metal pentatellurides ZrTe5 and HfTe5 as largegap quantum spin Hall insulators [4]. This prediction has sparked intense experimental and theoretical activity on this material system, in the monolayer form and in the bulk. ZrTe5 has proved a fertile ground for the discovery of a number of exciting properties: chiral magnetic effect [5], log-periodic quantum oscillations [6], three-dimensional quantum Hall effect [7], and quantized thermoelectric Hall conductivity [8], to list just a few Despite this broad-ranging interest, the topological nature of bulk ZrTe5 has not been unambiguously identified and has led to considerable debate.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
