Interfacial superconductivity and a Se-vacancy ordered insulating phase in the FeSe/PbOx heterostructures

TL;DR

This study fabricates FeSe/PbOx heterostructures, revealing interfacial superconductivity and an insulating phase with Se-vacancy order, highlighting the role of work function differences and charge transfer in inducing superconductivity.

Contribution

It reports the first fabrication of FeSe/PbOx heterostructures with observed superconductivity and a novel insulating phase with ordered Se vacancies, advancing understanding of interface-induced superconductivity.

Findings

Superconducting gaps of 13-14 meV in FeSe on PbOx

Discovery of a new insulating Fe10Se9 phase with Se-vacancy order

Superconductivity with a 5 meV gap in FeSe on insulating phase

Abstract

The discovery of high-temperature superconductivity in FeSe/SrTiO3 has sparked significant interests in exploring new superconducting systems with engineered interfaces. Here, using molecular beam epitaxy growth, we successfully fabricate FeSe/PbOx heterostructures and discover superconductivities in three different monolayer FeSe-related interfaces. We observe superconducting gaps of 13~14 meV in the monolayer FeSe films grown on two different phases of PbOx. Moreover, we discover a new insulating Fe10Se9 phase with an ordered $\sqrt{5}\times\sqrt{5}$ Se-vacancy structure. Our first-principles calculation suggests that this new insulating phase originates from electronic correlation. Intriguingly, an additional monolayer FeSe film grown on the insulating Fe10Se9 also exhibits superconductivity with the gap size of 5 meV. Our results suggest that the work function differences between the monolayer FeSe and the substrates, which can induce band bending and charge transfer, are crucial for the interfacial superconductivity.