Weak electronic correlations in the cobalt oxychalcogenide superconductor Na2CoSe2O

Abstract

Motivated by the newly discovered Co-based superconductor Na2CoSe2O, we performed systematic calculations of its electronic band structures using the density functional theory (DFT) plus the dynamical mean-field theory (DMFT) approaches. Our comparative studies reveal weakly correlated and itinerant nature of the Co-3d electrons and show no sign of fluctuating local moments as expected in many other unconventional superconductors, although the Co eg orbitals are close to half filling. These suggest that Na2CoSe2O is a normal paramagnetic metal and its superconductivity might not be of strongly correlated nature, contrary to the initial speculation. We suggest future investigations of electron-phonon interactions to clarify its pairing mechanism.