Electronic structure ofK3Ba3C60andRb3Ba3C60superconductors

Abstract

We have studied the electronic structure of the superconducting fullerides ${\mathrm{K}}_{3}{\mathrm{Ba}}_{3}{\mathrm{C}}_{60}$ and ${\mathrm{Rb}}_{3}{\mathrm{Ba}}_{3}{\mathrm{C}}_{60}$ using the local-density approximation in the density functional theory. Their conduction-band profiles are found to be quantitatively very similar to each other although the lattice constant of ${\mathrm{K}}_{3}{\mathrm{Ba}}_{3}{\mathrm{C}}_{60}$ is definitely smaller than that of ${\mathrm{Rb}}_{3}{\mathrm{Ba}}_{3}{\mathrm{C}}_{60}.$ The density of states at Fermi level of ${\mathrm{K}}_{3}{\mathrm{Ba}}_{3}{\mathrm{C}}_{60}$ is slightly larger than that of ${\mathrm{Rb}}_{3}{\mathrm{Ba}}_{3}{\mathrm{C}}_{60}.$ In addition, ${\mathrm{C}}_{60}$ states are found to be hybridized not only with Ba states but also with K (Rb) states. These results are in sharp contrast to ${A}_{3}{\mathrm{C}}_{60}$ superconductors $(A=\mathrm{K}$ and Rb). The hybridization is expected to play an important role in their superconducting properties since carriers are found to be not only on ${\mathrm{C}}_{60}$ but also around K (Rb) sites as well as Ba sites.