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Functional Approaches to Superconductivity within an Extended Attractive Hubbard Model
Author(s) -
Teubel A.,
Kolley E.,
Kolley W.
Publication year - 1990
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.2221570139
Subject(s) - hubbard model , pairing , superconductivity , physics , spins , saddle point , formalism (music) , saddle , functional derivative , energy functional , self energy , nonlinear system , hamiltonian (control theory) , quantum mechanics , condensed matter physics , quantum electrodynamics , mathematics , art , musical , mathematical optimization , geometry , visual arts , electron
On the basis of an extended attractive Hubbard model with nearest‐neighbour interaction of opposite spins two functional methods are adopted for deriving a self‐consistent equation for the superconducting order parameter. The functional‐integral formalism is exploited in saddle‐point approximation. The functional‐derivative technique using Schwinger source fields leads via the self‐energy in Hartree‐Fock‐Bogolubov approximation to a nonlinear gap equation. The superconducting transition temperature is investigated for the case of s‐wave pairing.