Figure 4: The time-evolution of the exciton distribution distinguishing various processes.

(a,b) Exciton population difference ΔN_1s,2p (red diamonds), ΔN_1s,3p (blue dots) as a function of time delay in a logarithmic scale at 8 K for 790 nm (550 μJ cm⁻²) and 399 nm (120 μJ cm⁻²) excitation, respectively. The detailed THz time scan with 50 fs resolution is shown together in a. The error bars of carrier densities indicate the uncertainty from theoretical fitting of the experimental results. (c) The time-dependent density N_eh of unbound carriers for two pumping conditions. (d) Time-dependent ratios of the population difference ΔN_1s,2p/ΔN_1s,3p are shown in the inset, which allows to extract the cooling curves for two pumping conditions. (e) The photoinduced THz transmission under 790 nm and 550 μJ cm⁻² pumping for various temperatures. A two-step rise, ∼1.0±0.03 ps (grey) and ∼11.2±1.06 ps (cyan) is separated for the 8 K trace.