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 <2 for positive tetragonal distortions as present in Sr2IrO4, the experiment indicates g∥>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.
@article{arxiv.1604.07780,
title = {Orbital reconstruction in nonpolar tetravalent transition-metal oxide layers},
author = {Nikolay A. Bogdanov and Vamshi M. Katukuri and Judit Romhányi and Viktor Yushankhai and Vladislav Kataev and Bernd Büchner and Jeroen van den Brink and Liviu Hozoi},
journal= {arXiv preprint arXiv:1604.07780},
year = {2016}
}