Dependence of the gap ratio on the fermi level shift in a van hove superconductor

Abstract

The dependence of the zero temperature gap to the critical temperature for s- and d-wave superconductors on the Fermi level shift (δ) from the Van Hove singularity is studied within the BCS theory. Exact numerical calculations for the s and d gap ratios are carried out and approximate analytic expressions for the ratio are given. We find that the maximum gap ratio occurs at δ = 0 and it decreases slowly with increasing δ, and that this behavior is symmetric with respect to δ. ©2000 Plenum Publishing Corporation.