Upper limit for the T c's of the “new” high T c superconductors

Abstract

Expressions for the transition temperatures of multilayer superconductors such as the recently discovered high T c bismuth and thallium superconductors are obtained within the framework of a Ginzburg-Landau approach. Using the values of the T c's of the one-and two-layer superconductors, the T c's of the compounds having higher number of layers are calculated. The predicted value for the three-layer thallium superconductor is in agreement with the observed T c. It is seen that there is an upper limit to the T c's which can be achieved by inserting additional CuO/Ca double layers into each superconducting series.