Fig. 3: CPFB at selected delays between the two pump pulses.
From: Coherent phonon flatband generated in GaAs/AlAs superlattices via layer-selective optical pumping
a The temporal evolution of the XRD intensity at Q = 0.02 for various pump delay times, Δτ*, indicated in the units of the CPFB oscillation periods. Time zero (t = 0 ps) on the horizontal axis marks the arrival of the second optical pump pulse. b, c Coherent phonon dispersions for two cases of pump delay time: (b) Anti-phase (Δτ* = 0.5 is half the oscillation period of the CPFB) and c in-phase (Δτ* = 1.0 is one oscillation period of the CPFB). For comparison, the red open circles represent the phonon dispersions of an 8 nm/8 nm GaAs/AlAs SL obtained from equilibrium-state lattice dynamics calculation.
