Superconductivity in the Tl-Ca-Ba-Cu-O System: synthesis, characterization and mechanism

Abstract

Synthesis and characterization of some of the members of the Tl-Ca-Ba-Cu-O system are presented. T_c in both the TlCa_n-1Ba₂Cu_nO_2n+3 and Tl₂Ca_n-1Ba₂Cu_nO_2n+4 series increase with the number of Cu-O layers, n; T_c in the latter series with two Tl-O layers are generally higher than in the former with a single Tl-O layer. Tl in the cuprates is in the 3+ state while Cu is in the 1+ and 2+ states, showing the importance of oxygen holes. The concentration of these holes seems to increase with the number of Tl-O layers.