Orbital reconstruction in nonpolar tetravalent transition-metal oxide layers

• Published in: Nature communications Vol. 6; no. 1; p. 7306
• Main Authors: Bogdanov, Nikolay A., Katukuri, Vamshi M., Romhányi, Judit, Yushankhai, Viktor, Kataev, Vladislav, Büchner, Bernd, van den Brink, Jeroen, Hozoi, Liviu
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 24.06.2015; Nature Publishing Group; Nature Pub. Group
• Subjects: 119/118; 639/301/119/995; Humanities and Social Sciences; multidisciplinary; Science; Science (multidisciplinary)
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/ncomms8306

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 Sr 2 IrO 4 by electron spin resonance. While canonical ligand-field theory predicts g || -factors less than 2 for positive tetragonal distortions as present in Sr 2 IrO 4 , 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 Sr 2 IrO 4 , whereas we find them in Ba 2 IrO 4 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. The iridate compounds display interesting physical properties, including quasi-two-dimensional behaviour similar to cuprates. Bogdanov et al. explore the d -level structure of Sr 2 IrO 4 using electron spin resonance measurements and detailed calculations and find it is inverted compared to its normal ordering