Magnetic transitions and superconductivity in the t-J model

Abstract

With the use of the spin-wave and Born approximations the energy spectrum of the two-dimensional t-J model is self-consistently calculated in the range of hole concentrations, 0⩽x≲0.3. The anomalous magnon Green's functions, which arise due to the hole-magnon interaction, are taken into consideration. They lead to a sharp transition from short-range antiferromagnetic order to a completely disordered paramagnetic state at x≈0.19, in addition to the transition from long-range to short-range antiferromagnetic order at x≈0.02–0.04. In the region of hole concentrations 0.04≲x≲0.19 the obtained shape of the Fermi surface, the hole dispersion near the Fermi level, and the density of states on it are in satisfactory agreement with experiment in La2−xSrxCuO4 and Bi2212. The Eliashberg formalism is used for calculating Tc. The hole-magnon interaction is found to be unable alone to give rise to superconductivity. By adding a moderate interaction with apex oxygen vibrations high Tc's are obtained for even-frequency dx2−y2 pairing in the range 0.04≲x≲0.19. For larger hole concentrations the odd-frequency s-wave solution becomes the leading one which can lead to s-wave superconductivity in the overdoped regime with the participation of a hole-phonon interaction of the respective symmetry.

Source-reported materials — not catalogue approval

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