High-temperature superconductivity and band antiferromagnetism

Abstract

We analyze the competition between high-temperature superconductivity (SC) and antiferromagnetism (AF) using the extended Hubbard model containing following matrix elements in the Hamiltonian: Hund's on-site field F H, single-site Coulomb repulsion U = ( i , i | 1 / r | i , i ) , two-site charge–charge, exchange, pair exchange and assisted hopping interactions V = ( i , j | 1 / r | i , j ) , J = ( i , j | 1 / r | j , i ) , J ′ = ( i , i | 1 / r | j , j ) , Δ t = ( i , i | 1 / r | j , i ) . In our model, we introduce the possibility of AF ordering by dividing the crystal lattice into two interpenetrating sub-lattices α , β . We use Hartree–Fock (H–F) approximation for all interactions except the strong on-site Coulomb repulsion. The self-energies Σ γ σ ( ε ) ( γ = α , β ) are calculated within the coherent potential approximation (CPA). To obtain the SC transition temperature T C and the Néel's temperature T N we solve the coupled equations of motion for the Green's functions. We present numerical results. They show that the AF at half-filling destroys the superconductivity of the s 0-wave symmetry. Increase of the Coulomb repulsion in the CPA causes increasing dumping of s 0-wave SC, shifts it away from the half-filling point, enhances SC temperature for sub-lattice magnetic moments; 0< m<0.28 μ B.