Interfacial charge-transfer in 3d/5d complex oxide heterostructures

TL;DR

This study systematically investigates charge transfer at 3d/5d oxide interfaces, revealing electronegativity mismatch as a key factor for designing electronic and spin states in complex heterostructures.

Contribution

It establishes a quantitative framework for interfacial charge transfer driven by electronegativity differences, enabling predictive design of oxide heterostructures.

Findings

Charge transfer up to 0.35 e per unit cell quantified.

ICT scales linearly with electronegativity difference.

Spin-state conversion induced by interface-controlled hybridization.

Abstract

Interfacial charge transfer (ICT) provides a powerful route to engineer electronic phases in correlated oxide heterostructures, yet predictive design principles remain elusive. Here, we systematically investigate superlattices composed of the 5d spin-orbit coupled semimetal SrIrO3 and a series of correlated 3d perovskites (LaMnO3, LaFeO3, LaCoO3, and NdNiO3), thereby establishing a quantitative framework for ICT across 3d/5d interfaces. Combining element-specific x-ray absorption spectroscopy with spatially resolved electron energy loss spectroscopy, a homogeneous electron transfer from the 5d to the 3d layers is directly quantified, reaching up to 0.35 e per unit cell in the cobaltate superlattice. We show that the magnitude of ICT scales linearly with the difference in electronegativity between the transition-metal oxide layers, identifying electronegativity-driven band alignment as the dominant mechanism for ICT. Beyond interfacial doping, we find that strong 3d-5d hybridization induces a complete low-spin to high-spin conversion in the cobaltate layers, demonstrating interface-controlled spin-state engineering without chemical substitution. These results establish electronegativity mismatch as a predictive design parameter for correlated oxide interfaces and provide a materials platform for tailoring band filling, orbital hierarchy, and spin configurations in quantum oxide heterostructures, paving the way towards advanced oxide electronics and next-generation information technologies.