Thermal robustness of the quantum spin Hall phase in monolayer WTe${}_2$

Abstract

Monolayer 1T'-WTe${}_2$ has been the first two-dimensional crystal where a quantum spin Hall phase was experimentally observed. In addition, recent experiments and theoretical modeling reported the presence of a robust excitonic insulating phase. While first-principles calculations with hybrid functionals and several measurements at low temperatures suggest the presence of a band gap of the order of 50 meV, experiments could confirm the presence of the helical edge states only up to 100 K. Here, we study with first-principle simulations the temperature effects on the electronic structure of monolayer 1T'-WTe${}_2$ and consider the contributions of both thermal expansion and electron-phonon coupling. First, we show that thermal expansion is weak but tends to increase the indirect band gap. Then, we calculate the effect of electron-phonon coupling on the band structure with non-perturbative methods and observe a small reduction of the band inversion with increasing temperature. Notably, the topological phase and the presence of a finite gap are found to be particularly robust to thermal effects up to and above room temperature.

6 pages, 4 figures + supplementary material (1 page, 1 figure)

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Cited by in corpus (2)

• Temperature effects in topological insulators of transition metal dichalcogenide monolayers
• Unusual temperature dependence of the band structure associated with local atomic distortion in monolayer 1T'-WTe2