Interfacial charge transfer and persistent metallicity of ultrathin SrIrO ₃ /SrRuO ₃ heterostructures

Interface quantum materials have yielded a plethora of previously unknown phenomena, including unconventional superconductivity, topological phases, and possible Majorana fermions. Typically, such states are detected at the interface between two insulating constituents by electrical transport, but whether either material is conducting, transport techniques become insensitive to interfacial properties. To overcome these limitations, we use 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 SrIrO 3 and the correlated metallic Weyl ferromagnet SrRuO 3 . We find that electrons are transferred from the SrIrO 3 to SrRuO 3 , with an estimated screening length of λ = 3.2 ± 0.1 Å. In addition, we find that metallicity is preserved even down to a single SrIrO 3 layer, where the dimensionality-driven metal-insulator transition typically observed in SrIrO 3 is avoided because of strong hybridization of the Ir and Ru t 2 g states.