Competition between covalent bonding and charge transfer at complex-oxide interfaces

TL;DR

This study investigates the electronic interactions at cuprate/manganite interfaces, revealing a complex charge transfer profile influenced by multiple competing factors, which advances understanding of oxide interface physics.

Contribution

It provides the first atomic-scale map of charge transfer and oxidation states at cuprate/manganite interfaces, highlighting the interplay of chemical bonding and band mismatch effects.

Findings

Non-monotonic charge transfer profile observed

Electrons transfer from manganite to cuprate

Charge transfer influenced by chemical bonding and substitution effects

Abstract

Here we study the electronic properties of cuprate/manganite interfaces. By means of atomic resolution electron microscopy and spectroscopy, we produce a subnanometer scale map of the transition metal oxidation state profile across the interface between the high $T_c$ superconductor YBa$_2$Cu$_3$O$_{7-\delta}$ and the colossal magnetoresistance compound (La,Ca)MnO$_3$. A net transfer of electrons from manganite to cuprate with a peculiar non-monotonic charge profile is observed. Model calculations rationalize the profile in terms of the competition between standard charge transfer tendencies (due to band mismatch), strong chemical bonding effects across the interface, and Cu substitution into the Mn lattice, with different characteristic length scales.