Interface reconstruction in superconducting CaCuO2/SrTiO3 superlattices: A hard x-ray photoelectron spectroscopy study

TL;DR

This study investigates the interface reconstruction in CaCuO2/SrTiO3 superlattices using hard x-ray photoelectron spectroscopy, revealing oxygen redistribution as key to enabling superconductivity without direct charge transfer.

Contribution

It demonstrates that oxygen redistribution at interfaces suppresses electrostatic potential, allowing hole doping and superconductivity in CaCuO2/SrTiO3 superlattices.

Findings

Valence band alignment prevents electronic reconstruction.

Oxygen redistribution suppresses built-in potential.

Superconductivity arises from oxygen doping under oxidizing conditions.

Abstract

Here we report about the interface reconstruction in the recently discovered superconducting artificial superlattices based on insulating CaCuO2 and SrTiO3 blocks. Hard x-ray photoelectron spectroscopy shows that the valence bands alignment prevents any electronic reconstruction by direct charge transfer between the two blocks. We demonstrate that the electrostatic built-in potential is suppressed by oxygen redistribution in the alkaline earth interface planes. By using highly oxidizing growth conditions, the oxygen coordination in the reconstructed interfaces may be increased, resulting in the hole doping of the cuprate block and thus in the appearance of superconductivity.