Exploring the spin wave and the flat band of Co3Sn2S2 by RIXS

A recent inelastic neutron scattering study on Co3Sn2S2 reported low-energy spin waves up to 40 meV and a resonant inelastic X-ray scattering (RIXS) study with linear polarized incident X-rays reported correlation driven near-flat band Stoner excitations. However, our RIXS measurements at the ADRESS/SLS employing a magnetic circular dichroism (MCD) analysis suggests that the “near-flat band” is quite dispersive and its intensity reduces upon approaching Tc. Applying a magnetic field of 0.1 T to fully polarize the spin will allow extracting the dynamic magnetism with circular polarized X-ray. However, due to limited energy resolution, we were unable to clearly resolve the spin waves from the asymmetric elastic peak. We therefore propose here to study Co3Sn2S2 by high-resolution MCD RIXS at ID32 to resolve the spin wave excitations, including the acoustic and optical mode, in which the latter is more likely to form the “true” flat band due to the kagome lattice structure.