Pairing mechanism from dielectric response in high Tc superconductors

Minimization of the total energy in Y BaCuO implies that the electronic transferences occur between p and d orbitals of the CuO2 sheets and CuO3 chain. This leads to the appearance of d and p holes in the Cu2 and O2 O3 atoms repectively. Screened interactions like W(ω) = [I-UII(ω)]- 1U defined in the p⊗d space produce attractive interactions in a defined range of frequencies whose upper limit is larger than the cutoff frequency ωc and the lower limit is less than ωc. We analyze the conditions of the band structure for which W(ω) implies coupling. The main question is whether ε(ω) may produce superconductivity for the band parameters of the superconducting phase of the YBaCuO systems. The dielectric functions given in this paper yield a hole-hole attractive potential strong enough for producing coupling. We analyze the different possibilities for the localization of these holes and we conclude that the interaction between two holes located on two different atoms (preferably one of them on a Cu atom and the other one on an O atom) produces coupling and possibly high Tc superconductivity. © 1990.