Interface-engineered hole doping in Sr₂IrO₄/LaNiO₃ heterostructure

The relativistic Mott insulator Sr₂IrO₄ driven by large spin-orbit interaction is known for the antiferromagnetic state which closely resembles the electronic structure of parent compounds of superconducting cuprates. Here, we report the realization of hole-doped Sr₂IrO₄ by means of interfacial charge transfer in Sr₂IrO₄/LaNiO₃ heterostructures. X-ray photoelectron spectroscopy on Ir 4f edge along with the x-ray absorption spectroscopy at Ni L ₂ edge confirmed that 5d electrons from Ir sites are transferred onto Ni sites, leading to markedly electronic reconstruction at the interface. Although the Sr₂IrO₄/LaNiO₃ heterostructure remains non-metallic, we reveal that the transport behavior is no longer described by the Mott variable range hopping mode, but by the Efros-Shklovskii model. These findings highlight a powerful utility of interfaces to realize emerging electronic states of the Ruddlesden-Popper phases of Ir-based oxides.