The magnon pairing mechanism of superconductivity in cuprate ceramics

Abstract

The magnon pairing mechanism is derived to explain the high-temperature superconductivity of both the LA2-xSrxCu1O 4 and Y1Ba2Cu3O7 systems. Critical features include (i) a one- or two-dimensional lattice of linear Cu-O-Cu bonds that contribute to large antiferromagnetic (superexchange) coupling of the CuII (d9) orbitals; (ii) holes in the oxygen pπ bands [rather than CuIII (d8)] leading to high mobility hole conduction; and (iii) strong ferromagnetic coupling between oxygen pπ holes and adjacent CuII (d9) electrons. The ferromagnetic coupling of the conduction electrons with copper d spins induces the attractive interaction responsible for the superconductivity, leading to triplet-coupled pairs called "tripgems." The disordered Heisenberg lattice of antiferromagnetically coupled copper d spins serves a role analogous to the phonons in a conventional system. This leads to a maximum transition temperature of about 200 K. For La1.85Sr0.15Cu 1O4, the energy gap is in excellent agreement with experiment. For Y1Ba2Cu3O7, we find that both the CuO sheets and the CuO chains can contribute to the supercurrent.