Finite-Band-width Effects on the Transition Temperature and NMR Relaxation Rate of Impure Superconductors

Abstract

We study the thermodynamic properties of impure superconductors by explicitly taking into consideration the finiteness of electronic bandwidths within the phonon-mediated Eliashberg formalism. For a finite electronic bandwidth, the superconducting transition temperature, $T_c$, is suppressed by nonmagnetic impurity scatterings. This is a consequence of a reduction in the effective electron-phonon coupling, ${\lambda }_{eff}$. The reduced ${\lambda }_{eff}$ is reflected in the observation that the coherence peak in $1/(T_{1}T)$, where $T_1$ is the nuclear spin-lattice relaxation time and $T$ is the temperature, is enhanced by impurity scatterings for a finite bandwidth. Calculations are presented for $T_c$ and $1/(T_{1}T)$ as bandwidths and impurity scattering rates are varied. Implications for doped C${}_{60}$ superconductors are discussed in connection with $T_c$ and $1/T_1$ measurements.

10 pages. REVTeX. 5 postscript figures. Scheduled to be published in Physical Review B, March 1. The previous submission is revised and two figures are added

References in corpus (1)

• Effects of Impurity Vertex Correction on NMR Coherence Peak in S-Wave Superconductors

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• Anomalous impurity effects in nonadiabatic superconductors
• s- and d-wave solution of Eliashberg equations with finite bandwidth
• The possible explanation of electric-field-doped C60 phenomenology in the framework of Eliashberg theory
• Electrical conductivity and nuclear magnetic resonance relaxation rate of Eliashberg superconductors in the weak-coupling limit
• Effect of Impurities Scattering Potential on NMR relaxation rate in impure d-wave superconductors