Superconductivity in nonstoichiometric rubidium-doped C₆₀ compounds

A rubidium-doped C₆₀ superconductor with a critical temperature (T_c) of 22-23 K synthesized by a wet-chemical method is well-defined from the magnetization and resistivity measurements based on the observations of the Meissner effect and zero resistivity state. Raman scattering measurements show the downshift of 15 cm^-1 for the A_g(2) vibrational mode, yielding the charge transfer is less than 3, which puts the new superconductor in the face-centred cubic structure based on the well-established phase diagram for this system. The superconducting parameters, such as the critical current density, the lower and upper critical field, and the derived coherence length and penetration depth, are determined from multiple techniques for this superconductor.