Fig. 2: Long-lived, light-induced phase in K3C60 generated with intense, 1-ps-long excitation pulses.
From: Evidence for metastable photo-induced superconductivity in K3C60
a, Schematic of the experimental set-up for pump–probe experiments producing 1-ps-long pump pulses centred at a mid-infrared (MIR) wavelength of 7.3 µm. These pulses have been generated in an optical parametric amplifier (OPA) and subsequent difference frequency generation (DFG) of the signal and idler beams. The 7.3-µm-wavelength, 100-fs-long pulses are stretched by linear propagation in a highly dispersive CaF2 rod. The photo-induced changes in the optical response of K3C60 upon irradiation are detected with transient terahertz time-domain spectroscopy using electro-optic sampling (EOS) for detection of the reflected terahertz field. b, Equilibrium reflectivity (sample–diamond interface), real and imaginary part of the optical conductivity of K3C60 measured at equilibrium (red lines), 10 ps, 300 ps and 12 ns (blue filled symbols) after photoexcitation. The blue shading indicates the change of spectral weight in these quantities induced by photoexcitation. The dark blue lines are Drude–Lorentz fits to the transient optical data (Supplementary Section 6). These data were acquired at a base temperature T = 100 K with a fluence of 18 mJ cm−2 and a pump-pulse duration of 1 ps.
