Fig. 4: The mechanism of tunable OTTs by Mo doping.
From: Tunable optical topological transitions of plasmon polaritons in WTe2 van der Waals films
a–c The experimental and fitting results of anisotropic extinction spectra of bare films of MoxW1-xTe2. Blue downward arrows represent the first interband transition resonances along b-axis. d–f The imaginary parts of conductivities along two crystal axes. Shaded areas denote the corresponding hyperbolic regimes. g Doping dependence of the frequency of the first interband transition resonance. h Doping dependence of the hyperbolic regime. Black right-pointing triangles are determined by fitted conductivities from (d–f) and shaded areas are the corresponding hyperbolic regimes. Red dots are determined by the polarization \({\phi }_{{{\max }}}=0^\circ\). Blue pentagrams are from the plasmon dispersion in ref. 13
