Fig. 2. Time-resolved THz reflectivity from MAPI after band-edge optical excitation.

(A) Differential reflectivity ∣Δr(ω, τ)∣/∣r₀∣ cuts at selected delay times τ marked in (B). (B) 2D-probe frequency/delay time color scale map for∣Δr(ω, τ)∣/∣r₀∣. (C to F) ∣Δr(ω, τ)∣/∣r₀∣ at the four probe frequencies 1.2, 2.8, 4.6, and 7.5 THz, respectively. The differential reflectivity amplitude is represented by blue curves, the fitted background exponential change is shown in red, and the differential reflectivity oscillations obtained by subtracting the slow exponential rise are shown in black.