BaCuS2: a superconductor with moderate electron-electron correlation

TL;DR

BaCuS2 is a layered superconductor with moderate electron-electron correlation, resembling cuprates and iron-based superconductors, offering a platform to study competing pairing mechanisms in high-temperature superconductivity.

Contribution

This work identifies BaCuS2 as a moderately correlated superconductor with a unique electronic structure, bridging cuprates and iron-based superconductors, and proposes it as a model system for studying pairing mechanisms.

Findings

Electronic structure similar to cuprates and iron-based superconductors.

Isolation of in-plane $d$-$p$ $\sigma^*$-bonding bands near the Fermi level.

Moderate electron correlation due to small energy separation between $d$ and $p$ orbitals.

Abstract

We show that the layered-structure BaCuS$_2$ is a moderately correlated electron system in which the electronic structure of the CuS layer bears a resemblance to those in both cuprates and iron-based superconductors. Theoretical calculations reveal that the in-plane $d$-$p$ $\sigma^*$-bonding bands are isolated near the Fermi level. As the energy separation between the $d$ and $p$ orbitals are much smaller than those in cuprates and iron-based superconductors, BaCuS$_2$ is expected to be moderately correlated. We suggest that this material is an ideal system to study the competitive/collaborative nature between two distinct superconducting pairing mechanisms, namely the conventional BCS electron-phonon interaction and the electron-electron correlation, which may be helpful to establish the elusive mechanism of unconventional high-temperature superconductivity.