BaCuS2: A Superconductor with Moderate Electron-Electron Correlation* *Supported by the National Key R&D Program of China (Grant No. 2017YFA0303100), the National Natural Science Foundation of China (Grant No. 11888101), and the Strategic Priority Research Program of CAS (Grant No. XDB28000000).

Abstract

We show that the layered-structure BaCuS2 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 σ *-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, BaCuS2 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.