title: Orbital reconstruction in nonpolar tetravalent transition-metal oxide layers.
abstract: A promising route to tailoring the electronic properties of quantum materials and devices rests on the idea of orbital engineering in multilayered oxide heterostructures. Here we show that the interplay of interlayer charge imbalance and ligand distortions provides a knob for tuning the sequence of electronic levels even in intrinsically stacked oxides. We resolve in this regard the d-level structure of layered Sr2IrO4 by electron spin resonance. While canonical ligand-field theory predicts g||-factors less than 2 for positive tetragonal distortions as present in Sr2IrO4, the experiment indicates g|| is greater than 2. This implies that the iridium d levels are inverted with respect to their normal ordering. State-of-the-art electronic-structure calculations confirm the level switching in Sr2IrO4, whereas we find them in Ba2IrO4 to be instead normally ordered. Given the nonpolar character of the metal-oxygen layers, our findings highlight the tetravalent transition-metal 214 oxides as ideal platforms to explore d-orbital reconstruction in the context of oxide electronics.
authors.affiliation: Institute for Theoretical Solid State Physics, IFW Dresden, Helmholtzstr. 20, 01069 Dresden, Germany.
authors.forename: Nikolay A
authors.identifier: http://orcid.org/0000-0002-5437-4919
authors.initials: NA
authors.lastname: Bogdanov
authors.affiliation: Institute for Theoretical Solid State Physics, IFW Dresden, Helmholtzstr. 20, 01069 Dresden, Germany.
authors.forename: Vamshi M
authors.initials: VM
authors.lastname: Katukuri
authors.affiliation: Institute for Theoretical Solid State Physics, IFW Dresden, Helmholtzstr. 20, 01069 Dresden, Germany.
authors.forename: Judit
authors.initials: J
authors.lastname: Romhányi
authors.affiliation: Institute for Theoretical Solid State Physics, IFW Dresden, Helmholtzstr. 20, 01069 Dresden, Germany.|Joint Institute for Nuclear Research, Joliot-Curie 6, 141980 Dubna, Russia.
authors.forename: Viktor
authors.initials: V
authors.lastname: Yushankhai
authors.affiliation: Institute for Solid State Research, IFW Dresden, Helmholtzstr. 20, 01069 Dresden, Germany.
authors.forename: Vladislav
authors.initials: V
authors.lastname: Kataev
authors.affiliation: Institute for Solid State Research, IFW Dresden, Helmholtzstr. 20, 01069 Dresden, Germany.|Department of Physics, Technical University Dresden, 01062 Dresden, Germany.
authors.forename: Bernd
authors.initials: B
authors.lastname: Büchner
authors.affiliation: Institute for Theoretical Solid State Physics, IFW Dresden, Helmholtzstr. 20, 01069 Dresden, Germany.|Department of Physics, Technical University Dresden, 01062 Dresden, Germany.
authors.forename: Jeroen
authors.initials: J
authors.lastname: van den Brink
authors.affiliation: Institute for Theoretical Solid State Physics, IFW Dresden, Helmholtzstr. 20, 01069 Dresden, Germany.
authors.forename: Liviu
authors.initials: L
authors.lastname: Hozoi