L. Tewordt et T. Dahm, SUPERCONDUCTIVITY IN AN EXTENDED HUBBARD-MODEL DUE TO SPIN AND CHARGEFLUCTUATIONS, Physica. C, Superconductivity, 235, 1994, pp. 2163-2164
The eigenvalues of the superconducting states of the three-band Hubbar
d model are calculated as functions of band-filling n, on-site repulsi
on U, and Cu-O repulsion V. We take full into account the momentum and
energy dependence of the pairing interaction due to exchange of spin
and charge fluctuations. Near the spin-density-wave instability the le
ading eigenvalue is that of the pairing state with d(x)2(-y)2 symmetry
. This eigenvalue, lambda(d), increases rapidly and passes through uni
ty as V is increased towards the charge-density-wave instability. The
superconducting order parameter phi(d)(($) over right arrow k,omega) s
hows a ($) over right arrow k-dependence which deviates substantially
from the simplest form cos (pi k(x)) - cos (pi k(y)), and Im phi(d)(($
) over right arrow k,omega) exhibits a large and narrow peak as functi
on of omega at the characteristic energy of the spin fluctuation mode.