Fig. 3
Frequency-independent dynamics of THz spectra at high temperature. a Pump-induced THz spectra of Δσ1(ω) after 248 meV (5 μm) photoexcitation with fluence 12 μJ cm−2 at T = 300 K as a function of pump-probe delay Δtpp. b THz conductivity Δσ1(ω) from three cut positions from a, at Δtpp = 1, 5, 16 ps, as indicated by the white-dashed lines. c THz spectra of Δε1(ω) at Δtpp = 1 ps for 5 K (gray dots) and 300 K (black dots), the amplitude of which is much smaller at high temperature, opposite to low temperature ones in Fig. 2c, d. d The comparison of THz conductivity Δσ1(ω) at three frequencies: 2, 5, and 7 meV, as a function of Δtpp (scaled to match amplitude), from three frequency-cut positions from a as indicated by magenta, blue, and black dots, respectively. The frequency-independent relaxation dynamics of Δσ1(ω) indicates the strong coupling of surface and bulk states that make them decay together at high temperature
