BCS-universal ratios within the Van Hove scenario

Abstract

The central result of BSC theory is the Universal Ratios which do not depend on physical parameters of the particular superconductor under study. Several attempts have been made to introduce the Van Hove Scenario within BCS theory. We present here a formulation that allow us to obtain Universal Ratios independent of any parameters and therefore a precise definition of “deviation from BCS theory”. This concept is at the basis of several applications of BCS theory in characterizing conventional superconductors and should be useful as a reference value for high- T c superconductivity new theories.