Superconductivity and Magnetism in BiOCuS

TL;DR

This paper investigates the electronic and magnetic properties of hole-doped BiOCuS, suggesting it is near ferromagnetic instability and likely exhibits spin-fluctuation-mediated superconductivity rather than conventional phonon-mediated pairing.

Contribution

It provides theoretical insights into the magnetic tendencies of doped BiOCuS, challenging the idea of conventional superconductivity in this material.

Findings

BiOCuS is a band insulator when stoichiometric.

Hole doping brings BiOCuS close to ferromagnetic instability.

Superconductivity in doped BiOCuS is likely mediated by spin fluctuations.

Abstract

BiOCu_{1-y}S was recently reported to superconduct at T=5.8 K at y~0.15. Band structure calculations indicate that stoichiometric BiOCuS is a band insulator. In this paper, I show that hole-doped (whether in the virtual crystal approximation or with actual Cu vacancies) BiOCuS is on the verge of a ferromagnetic instability (cf. Pd metal), and therefore conventional superconductivity with Tc~6 K is quite unlikely. Presumably, hole-doped BiOCuS is another example of superconductivity mediated by spin-fluctuations