Effect of pseudogap on the isotope exponent of high-Tc superconductors

Abstract

The purpose of this paper is to explain the unusual isotope coefficients of cuprates by considering the influence of a pseudogap and phononic and electronic interactions in weak-coupling limit. Exact analytic expressions of the isotope exponent (α) for the s- and d-wave pairing symmetry are derived. It is found that α can fit the experimental data well and that the presence of the pseudogap increases α in the low-Tc region, but has no effect in the high-Tc region.