Unusual electronic behavior at the interface of Iridate-Nickelate (5d-3d) heterostructures*

The complex physics of transition metal oxides (TMOs)-based heterostructures with atomically sharp interfaces leads the way to unveil several novel functionalities which cannot be realized in the constituent bulk counterparts. The bi-layer thin films made of strongly correlated 3d PrNiO₃ (PNO) and 5d SrIrO₃ (SIO) with strong spin-orbit coupling (SOC), are indeed exceptionally fascinating in which the tuning of interface properties as a function of correlations/SOC strength of the constituents can be achieved. PNO exhibits a temperature-dependent phase transition from Antiferromagnetic (AFM) Insulator to Paramagnetic Semimetal and SIO possess a Paramagnetic Semimetal ground state. PNO is well known to exhibit physical properties depending on the oxygen stoichiometry. On the other hand, SIO has shown nontrivial quantum states through the Dzyaloshinskii−Moriya interaction associated with the strong SOC while being intercalated with other TMOs. Our high-quality PNO/SIO bilayers grown on SrTiO₃ substrate exhibit very distinct electronic behavior upon the change of the layer stacking order. Additionally, with the controlled inclusion of oxygen vacancies, this contrasting behavior becomes even more prominent, and an unexpected metallicity sets down to 5K. Our X-ray absorption spectroscopy study further reveals that the unusual kind of charge-transfer phenomenon occurs at the 5d-3d interface.