Effects of phonons and antiferromagnetic spin fluctuations on the pairing and density of states in high-T c superconductors

Abstract

We solve the Eliashberg equations for a two-dimensional, tight-binding band and anisotropic interaction due to exchange of phonons and antiferromagnetic spin fluctuations. For small band fillings, a mixture of simple and extendeds-wave pairing is stable, while for band fillings closer to half-filling thed-wave pairing state becomes stable. The density of statesN(ω) becomes highly asymmetric in ω for smaller band fillings, which is an effect of particle-hole asymmetry. For thed-wave stateN(ω) is linear in ω for small ω and exhibits a logarithmic singularity at the gap amplitude. For the mixeds-wave stateN(ω) shows the BCS singularity at the gap edge. Antiferromagnetic spin fluctuations give rise to a pseudogap inN(ω) for the normal state.