Fig. 3

Spin excitation of \(\hbox {La}_{2}\hbox {CuO}_4\) in incident-energy-dependent Cu L -edge RIXS. (a) Cu L-edge RIXS spectra of \({\bf{q}}_{\Vert }\) \(=(0.5\pi , 0)\) for various incident energies across the Cu \(L_3\)-edge. Spectra are plotted with a vertical offset for clarity. The spectral components of magnon and bimagnon from the curve fitting to the RIXS spectrum induced by x-ray energy of \(L_{3}+0.6\) eV are plotted in colors. The dotted lines plot the elastic and the phonon components. See the supplementary material for the curve-fitting details. (b) Two-dimensional RIXS intensity map measured across the Cu \(L_3\)-edge. (c) The peak height of the magnon (blue square) and bimagnon (red square) components from the fitting as a function of incident photon energy across the \(L_3\)-edge. Solid lines plot Lorentizian distribution curves to highlight the resonance along with XAS (gray dashed lines).