Investigating Superconductivity in Barium Bismuthate

Hole-doped BaBiO3 has a rather high critical superconducting temperature Tc at ~30-40K. Density functional calculations suggest a rather modest electron phonon coupling. This strongly suggests looking for either other mechanisms or for mechanism by which the electron phonon coupling might be strongly enhanced. A strong enhancement could also lead to rather small polaron behaviour leaning more towards a Bose Einstein Condensation theory. Recent interpretation of the density functional calculations of BaBiO3 strongly suggests that there is a condensation of two mainly O holes connected to the short bond length Bi suggesting bipolaron behaviour in the hole doped materials. We study the possibility of superconductivity in BaBiO3 based on the idea of pre-formed pairs, using an effective model obtained from Density Functional Theory.