Van Hove scenario for a high T<inf>c</inf>superconductor having a (s+d)-wave symmetry order parameter

Abstract

The effects of having a van Hove singularity in the density of states on a high temperature superconductors having an (s + d)-wave symmetry order parameter (OP) are studied. It is assumed that superconductivity is due to the exchange of spin fluctuations. It is found that the two (s-wave and d-wave) components of the OP are determined by a set of coupled equations. Close to Tc′these equations are linear in Δsand Δdwhile at T = 0 K, they form a set of non-linear equations in the two components of the OP. The equations for T close to Tcare solved analytically to yield an expression for the transition temperature Tc. The equations for T = 0 K are solved numerically for different values of ωb(the cutoff frequency of the magnetic excitation responsible for superconductivity in the system). The dependence of the ratio 2Δ(0)/kBTc(with Δ(0) = Δs(0)√(1 + R2) and R being the ratio of the two components of the OP at T = 0 K) on ωbis shown. © 2002 Published by Elsevier Science Ltd.