Fig. 4
Probe energy dependence of reflectivity changes in Nd2CuO4. a Time evolutions of ΔR/R for xph = 0.008 ph/Cu. The red, orange, green, and blue colors show the data at the probe energies (ħωr) of 1.88, 1.94, 2.03, and 2.10 eV, respectively, in (a–d) in common. b Oscillatory components ΔROSC/R extracted from ΔR/R. c Fourier power spectra of ΔROSC/R. Triangles indicate the oscillation frequencies ħΩn. d Probe energy dependence of ħΩn. The solid line shows the σ spectrum. The broad gray line is drawn from 1.73 eV (ħωCT) with the slope of 1 (see the text). e A two-magnon sideband is schematically shown as the shaded area. f Schematics of the magnon dispersion
