X-ray Absorption Spectroscopy Study of the Effect of Rh doping in Sr2IrO4

We investigate the effect of Rh doping in Sr 2 IrO 4 using X-ray absorption spectroscopy (XAS). We observed appearance of new electron-addition states with increasing Rh concentration (x in Sr 2 Ir 1−x Rh x O 4 ) in accordance with the concept of hole doping. The intensity of the hole-induced state is however weak, suggesting weakness of charge transfer (CT) effect and Mott insulating ground states. Also, Ir J eff = 1/2 upper Hubbard band shifts to lower energy as x increases up to x = 0.23. Combined with optical spectroscopy, these results suggest a hybridisation-related mechanism, in which Rh doping can weaken the (Ir J eff = 1/2)–(O 2 p ) orbital hybridisation in the in-planar Rh-O-Ir bond networks.