Renormalization of Coulomb interactions in s-wave superconductor Na${}_x$CoO${}_2$

Keiji Yada, Hiroshi Kontani

We study the renormalized Coulomb interactions due to retardation effect in Na${}_x$CoO${}_2$. Although the Morel-Anderson's pseudo potential for $a_{1g}$ orbital ${\mu }_{a1g}^{\ast }$ is relati…