Anomalous isotope effects of fulleride superconductors
نویسنده
چکیده
The numerical calculations of the standard Eliashberg-Nambu strong coupling theory and a formula of isotope effect derived in this paper provide direct evidences that an-harmonic vibrations of lattice enhance isotope effect with anomalous coefficient α > 1/2. The results in this paper explain very well the wide distributed α values for the samples with different ratios of substitutions of 12C by 13C of fulleride superconductor Rb3C60. The calculations of isotope effects indicate that the intra-molecule radial modes have more important contributions to superconductivity than the intra-molecule tangential modes with higher phonon frequencies PACS: 74.20.Fg, 74.70.Wz, 71.20.Tx, 81.05.Tp
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