Multiple Exchange-Mediated Interaction and Superconductivity

It is shown that in a strongly correlated system there exists multiple exchange-mediated interaction (MEIW). From the numerical calculations of T_c, (T_c vs. x and y for La_2-xSr_xCuO₄ and Y₁Ba₂Cu₃O_7-y), the small isotope effect, the large gap and some explanations for the observed phenomena, this paper affirms that the high-T, superconductivity is caused by the MEIW, the phonon-mediated interaction and the tunneling coupling. The heavy-fermion superconductivity is mainly caused by the MEMI, and, in the meantime, the phonon-mediated interaction h h also some contributions. The extremely large gap below T_N in AF Chevrel phase, some AF materials come from the MEMI. The organic superconductivity might be caused mainly by the MEMI.