Figure 2

The time-resolved ultra-broadband MIR ΔR/R spectra for Bi₂Te₂Se and Sb₂TeSe₂ single crystals and the schematics of the theoretical model: (a) and (b) the 2D plots of wavenumber- and time-resolved reflectance change (ΔR/R) spectra with an optical pump fluence of 101 μJ/cm² for Bi₂Te₂Se (a) and Sb₂TeSe₂ (b) single crystals. The red and green colors respectively represent the parts with a positive change and a negative change. The zero-crossing line is marked L_0× as a black dashed line. (c) shows the p-polarized reflectivity before pumping (R_p, gray solid-line. Assume N is 12.5 × 10¹⁸ cm⁻¹, so ω_p = 1880 cm⁻¹ with m^* = 0.32 and ε₀ = 23.7) and after pumping (R_p^*, red solid-line. Assume N is 25 × 10¹⁸ cm⁻¹ so ω_p = 2630 cm⁻¹ with m^* = 0.32 and ε₀ = 23.7) for the Drude model and (d) shows the p-polarized reflectivity before pumping (R_p, gray solid-line. Assuming μ = 50 meV at room temperature) and after pumping (R_p^*, red solid-line. Assuming μ = 40 meV at room temperature) for the SST-Kubo model.