Band Alignment Tuning from Charge Transfer in Epitaxial SrIrO$_3$/SrCoO$_3$ Superlattices

TL;DR

This study combines theoretical modeling and experimental synthesis to understand and control charge transfer at SrIrO$_3$/SrCoO$_3$ interfaces, enabling tailored electronic and magnetic properties in oxide superlattices.

Contribution

It demonstrates how DFT modeling and epitaxial growth can be used to tune charge transfer and band alignment in SIO/SCO superlattices, advancing oxide interface engineering.

Findings

Confirmed interfacial charge transfer from Ir to Co via XAS

Observed band alignment shifts consistent with DFT predictions

Achieved stabilization of perovskite SCO phase through charge transfer

Abstract

Understanding charge transfer at oxide interfaces is crucial for designing materials with emergent electronic and magnetic properties, especially in systems where strong electron correlations and spin-orbit coupling coexist. SrIrO$_3$/SrCoO$_3$ (SIO/SCO) superlattices offer a unique platform to explore these effects due to their contrasting electronic structures and magnetic behaviors. Building on past theory based on continuity of O 2p band alignment, we employ density functional theory (DFT) to model electron transfer from Ir to Co across the SIO/SCO interface. To characterize these effects, we synthesized epitaxial SIO/SCO superlattices via molecular beam epitaxy. Structural and transport measurements confirmed high crystallinity, metallic behavior, and suppression of Kondo scattering that has been reported in uniform SIO films. Further characterization via X-ray absorption spectroscopy (XAS) revealed orbital anisotropy and valence changes consistent with interfacial charge transfer. Co K- and L$_{2,3}$-edge and Ir L$_2$-edge spectra verified electron donation from Ir to Co, stabilizing the perovskite SCO phase and tuning the electronic structure of SIO via hole-doping. O K-edge XAS showed band alignment shifts in the SIO layer consistent with DFT predictions. Our work here provides a pathway for engineering oxide heterostructures with tailored magnetic and electronic properties.