Numerical analysis of coupled spin-fermion model emdash pairing mechanism through extended Kondo singlet

In this paper a coupled spin-fermion model is investigated by the exact diagonalization of finite lattices to discuss magnetic mechanism of superconductivity. An extended cloud of singlet liquid (extended Kondo singlet) is found around the fermion in a strong coupling region characterized by strong Kondo coupling and large transfer. The existence of the bound state of two fermions is found. The relevance of its Cooper pairing to high-Tc superconductivity is discussed. The relation to the weak coupling region and also to the small transfer region in this model is discussed