Interface-engineered hole doping in Sr2IrO4/LaNiO3 heterostructure*

The relativistic Mott insulator Sr2IrO4 is known for the Jeff = 1/2 Mott insulating state which closely resembles the electronic structure of parent compounds of superconducting cuprates. Here, by means of interface engineering of the Sr2IrO4/LaNiO3 heterostructure, the hole-doped phase of Sr2IrO4 has been realized with a markedly higher doping level close to 10%. X-ray absorption studies at Ni L2 edge confirmed that 5d electrons from Ir sites are transferred onto Ni sites leading to the formation of a high spin Ni2+ state. Despite the large amount of doping, Sr2IrO4/LaNiO3 heterostructure shows a non-metallic behavior but a narrower band gap compared to the bulk Sr2IrO4. This implies strong electronic reconstruction at the interfaces. These findings highlight a powerful utility of interfaces to realize emerging electronic states of the Ruddlesden-Popper phases of Ir-based oxides.