Reaction between different structural blocks and its influence on superconductivity in Tl2Ba2Can-1CunO2n+3

The non-monotonic relationship of T, with the number of Cu-O planes (n) per unit cell for compounds of Tl2Ba2Can-1CUnO2n+3 (n=1, 2, 3, 4 and 5) is investigated from the reaction between different structural blocks. The unit cell of the Tl superconductors is treated as two blocks: the perovskite block where the Cu-O planes are located and the rock salt block, which is considered as a charge-reservoir. A model was used to calculate the combinative energy of the two blocks. It is found that the combinative energy between the two blocks is closely related to the value of T-c. The relation demonstrates an interesting way to understand the nonlinear change of T, with the number of Cu-O planes in the layered superconductors. This means that the interaction between the two blocks plays an important role in superconductivity. The results are somewhat different from that of another Tl-system superconductor, Tl2Ba2Can-1CunO2n+4, with 4 superconductive compounds.