Figure 4

The time-evolution of ω_p, Γ, μ, T and the schematic energy band structure of TIs for pump/probe processes. The fitting results (a–d) and the pump-probe scheme (e) for Bi₂Te₂Se and (f–i) and for Sb₂TeSe₂ (j). (a,b) respectively show the time-evolution of the fitting parameter ω_p and Γ for the Drude model for a Bi₂Te₂Se crystal. (c,d) show the partial trace of the squared values of ω_p before c and after 3 ps (d) The red line in d shows the bi-exponential fitting that is described in the Method section. The green dashed lines in c marked by \({N}_{unex}^{(0)}\) (3.42 × 10⁷ cm⁻²) relate to the concentration of unexcited carriers and (d) marked by N⁽⁰⁾ (4.16 × 10⁷ cm⁻²) represent the height of the constant term from the fitting curve. The time-___domain traces for (f) ω_p, (g) Γ, (h) μ and (i) carrier temperature T are obtained using the Drude-SST-Kubo model. The red lines in (h), (i) show the single-exponential fitting that is mentioned in the Method section. The red arrows and pink arrows respectively show the 1.55 eV (800 nm) pumping and the MIR probing in (e), (j). The notation E_F in (e), (j) is the Fermi energy.