Fig. 5: Temperature-induced shifts of OTT energy in WTe2.
From: Tunable optical topological transitions of plasmon polaritons in WTe2 van der Waals films
a–d The anisotropic extinction spectra and fitting curves of a bare film of WTe2 at 78, 130, 155, and 230 K, respectively. e–h The corresponding extracted imaginary parts of the optical conductivities along two crystal axes in (a–d). The shaded area represents the hyperbolic regime. i–l The optimal polarization \({\phi }_{{\rm{\max }}}\) as a function of the plasmon frequency at 78, 130, 155, and 230 K, respectively. Dashed lines are calculated using the fitted optical conductivities in (e–h) at the corresponding temperature. Inset in (l) shows the temperature dependence of the hyperbolic regime determined by the corresponding extracted imaginary part of the optical conductivity (Supplementary Note 12)
