Formation, motion, and high-temperature superconductivity of large bipolarons

Although small (spatially compact) bipolarons readily localize, large bipolarons (like large polarons) can be mobile. As such, large bipolarons are a suitable basis for bipolaronic superconductivity. However, large bipolarons can only form in multidimensional ionic solids if the static dielectric constant greatly exceeds twice the optical dielectric constant. The formation as well as normal-state and superconducting properties of large bipolarons appear consistent with observations of the high-temperature superconductors.