Quasi-particle interference of heavy fermions in resonant x-ray scattering

Resonant x-ray scattering (RXS) has recently become an increasingly important tool for the study of ordering phenomena in correlated electron systems. Yet, the interpretation of RXS experiments remains theoretically challenging because of the complexity of the RXS cross section. Central to this debate is the recent proposal that impurity-induced Friedel oscillations, akin to quasi-particle interference signals observed with a scanning tunneling microscope (STM), can lead to scattering peaks in RXS experiments. The possibility that quasi-particle properties can be probed in RXSmeasurements opens up a new avenue to study the bulk band structure ofmaterials with the orbital and element selectivity provided by RXS. We test these ideas by combining RXS and STM measurements of the heavy fermion compound CeMIn5 (M = Co, Rh). Temperature-And doping-dependent RXSmeasurements at the Ce-M4 edge show abroad scattering enhancement that correlateswith the appearance of heavy f-electron bands in these compounds. The scattering enhancement is consistentwith themeasured quasi-particle interference signal in the STMmeasurements, indicating that the quasi-particle interference can be probed through the momentum distribution of RXS signals. Overall, our experiments demonstrate new opportunities for studies of correlated electronic systems using the RXS technique.