Theoretical Demonstration of How the Dispersion of Magnetic Excitations in Cuprate Compounds can be Determined Using Resonant Inelastic X-Ray Scattering

We show that in resonant inelastic x-ray scattering (RIXS) at the copper L and M edge direct spin-flip scattering is in principle allowed. We demonstrate how this possibility can be exploited to probe the dispersion of magnetic excitations, for instance magnons, of cuprates such as the high T(c) superconductors. We compute the relevant local and momentum dependent magnetic scattering amplitudes, which we compare to the elastic and dd-excitation scattering intensities. For cuprates these theoretical results put RIXS as a technique on the same footing as neutron scattering.