Discovery of superconductivity in cesium-doped C₆₀ at ambient pressure.

The early discovery of cesium-doped C₆₀ is a superconductor by the applied pressure. Here we report the superconductivity of cesium-doped C₆₀ obtained at ambient pressure from the resistance and magnetization measurements based on the observed zero-resistivity state and Meissner effect. X-ray diffraction shows that the new superconductor possesses the primitive cubic with space group of Pa-3, which is different from the structures reported for superconducting at high pressure. Raman spectroscopy measurements shows the 18 cm^-1 downshift to the frequency of A_g (2) mode compared with that of the pure C₆₀, providing the charge transfer of 3 electrons per C₆₀. The application of pressure is found to suppress the superconducting critical temperature, which is obviously different to the behavior in early found cesium-doped C₆₀ superconductors with body-centered cubic A15-structured and face-centred-cubic structures. Furthermore, the superconducting parameters such as the critical fields, Ginzburg-Landau coherence length and London penetration depth of the 21 K superconducting phase are determined for this new superconductor. This discovery provides a new idea for searching these molecules superconductors at ambient pressure.