Volume 47, Number 5, September I 1999
|Page(s)||588 - 594|
|Section||Condensed matter: electronic structure, electrical, magnetic and optical properties|
|Published online||01 September 2002|
Anomalous impurity effects in nonadiabatic superconductors
Dipartimento di Fisica, Università di Roma I "La Sapienza" and Piazzale A. Moro, 2, 00185 Roma, Italy
2 Istituto Nazionale Fisica della Materia, Unità di Roma 1 - Roma, Italy
Accepted: 5 July 1999
We show that, in contrast with the usual electron-phonon Migdal-Eliashberg theory, the critical temperature Tc of an isotropic s-wave nonadiabatic superconductor is strongly reduced by the presence of diluted nonmagnetic impurities. Our results suggest that the recently observed Tc-suppression driven by disorder in K3C60 (Phys. Rev. B, 55 (1997) 3866) and in NdCexCuO (Phys. Rev. B, 58 (1998) 8800) could be explained in terms of a nonadiabatic electron-phonon coupling. Moreover, we predict that the isotope effect on Tc has an impurity dependence qualitatively different from the one expected for anisotropic superconductors.
PACS: 71.38.+i – Polarons and electron-phonon interactions / 74.20.Mn – Nonconventional mechanisms (spin fluctuations, polarons and bipolarons, resonating valence bond model, anyon mechanism, marginal Fermi liquid, Luttinger liquid, etc.) / 74.62.Dh – Effects of crystal defects, doping and substitution
© EDP Sciences, 1999
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