ISSN:
1434-6036
Keywords:
PACS. 74.70.Wz Fullerenes and related materials – 74.20.-z Theories and models of superconducting state – 63.20.Kr Phonon-electron and phonon-phonon interaction
Source:
Springer Online Journal Archives 1860-2000
Topics:
Physics
Notes:
Abstract: In this paper, through an exhaustive analysis within the Migdal-Eliashberg theory, we show the incompatibility of experimental data of Rb3C60 with the basic assumptions of the standard theory of superconductivity. For different models of the electron-phonon spectral function α 2 F (Ω) we solve numerically the Eliashberg equations to find which values of the electron-phonon coupling λ, of the logarithmic phonon frequency and of the Coulomb pseudopotential μ * reproduce the experimental data of Rb3C60. We find that the solutions are essentially independent of the particular shape of α 2 F (Ω) and that, to explain the experimental data of Rb3C60, one has to resort to extremely large couplings: λ = 3.0±0.8. This results differs from the usual partial analyses reported up to now and we claim that this value exceeds the maximum allowed λ compatible with the crystal lattice stability. Moreover, we show quantitatively that the obtained values of λ and strongly violate Migdal's theorem and consequently are incompatible with the Migdal-Eliashberg theory. One has therefore to consider the generalization of the theory of superconductivity in the nonadiabatic regime to account for the experimental properties of fullerides.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/PL00011123
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