Interfacial charge transfer in atomically thin SrIrO₃ / SrRuO₃ heterostructures

Metallic interfacial quantum materials are most readily detected at the interface between two insulating constituents by probes such as electrical transport. However, when either material is conducting, transport techniques become insensitive to interfacial properties. To overcome these limitations, we employ angle-resolved photoemission spectroscopy and molecular beam epitaxy to reveal the electronic structure, charge transfer, doping profile, and carrier effective masses in a layer-by-layer fashion for the interface between the Dirac nodal-line semimetal SrIrO3 and the correlated metallic ferromagnet SrRuO3. Through comparisons with first-principles theory calculations, we determine that electrons are transferred from the SrIrO3 to SrRuO3, with an estimated screening length of 3.2± 0.1 Å. In addition, we find that metallicity is preserved even down to a single SrIrO₃ layer, where the dimensionality-driven metal-insulator transition typically observed in SrIrO₃ is avoided because of the strong hybridization of the Ir and Ru t_2g states.