On the role of the Coulomb interaction in the mechanism of d-wave Cooper pairing of charge carriers in high-T_c superconductors

The question of the effect of the structure of the anisotropic quasi-two-dimensional electron spectrum of high-T_c superconductors on the character of the screening of the Coulomb interaction and the symmetry of the superconducting order parameter is studied. Calculations of the polarization operator of electrons are performed on the basis of the single-particle band spectrum extracted from angle-resolved photoemission spectroscopy data. It is shown that the static screened Coulomb repulsion has a minimum at small momentum transfers. This corresponds to an effective electron-electron attraction in the d_x2-y2-wave channel of Cooper pairing of the charge carriers on account of their interaction with the long-wavelength charge-density fluctuations. This attraction together with the anisotropic electron-phonon interaction increase the critical superconducting transition temperature T_c with increasing hole density and can give quite high values of T_c while at the same time suppressing the isotope effect, in qualitative agreement with the experimental data for underdoped hole-type cuprate metal-oxide compounds. © 1999 American Institute of Physics.