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A superconductor with 4-fermion attraction weakly perturbed by magnetic impurities

Article

Abstract

A superconductor with 4-fermion attraction, considered by Maćkowiak and Tarasewicz is modified by adding to the Hamiltonian a long-range magnetic interaction V between conduction fermions and localized distinguishable spin 1/2 magnetic impurities. V has the form of a reduced s-d interaction. An upper and lower bound to the system’s free energy density f(H, β) is derived and the two bounds are shown to coalesce in the thermodynamic limit. The resulting mean-field equations for the gap Δ and a parameter y, characterizing the impurity subsystem are solved and the solution minimizing f is found for various values of magnetic coupling constant g and impurity concentration. The phase diagrams of the system are depicted with five distinct phases: the normal phase, unperturbed superconducting phase, perturbed superconducting phase with nonzero gap in the excitation spectrum, perturbed gapless superconducting phase and impurity phase with completely suppressed superconductivity.

PACS

74.20.-z Theories and models of superconducting state 74.25.Bt Thermodynamic properties 74.25.Dw Superconductivity phase diagrams 

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Copyright information

© Springer 2008

Authors and Affiliations

  1. 1.Instytut FizykiUniwersytet M. KopernikaTorunPoland

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