Prediction of several Co-based La$_3$Ni$_2$O$_7$-like superconducting materials

Abstract

High-temperature superconductivity has been found in Fe-, Ni-, and Cu-based compounds but has remained elusive in Co-based materials. The recent discovery of superconductivity in pressurized bilayer nickelate La$_3$Ni$_2$O$_7$ has renewed interest in related layered systems. Here, we predict several Co-based analogs that may realize similar physics. Electron doping of the high-pressure bilayer cobaltate La$_3$Co$_2$O$_7$ yields LaTh$_2$Co$_2$O$_7$, La$_3$Ni$_2$O$_5$Cl$_2$, and La$_3$Ni$_2$O$_5$Br$_2$, which exhibit closely related crystal structures and strongly correlated electronic states. Random-phase-approximation calculations reveal $s$-wave as the leading pairing symmetry in these compounds.