Combined effect of charge carriers and crystal structure on high-Tc superconductivity in codoped Y1-xCaxBa2-yLayCu3Oz.

• The combinative energy between the perovskite block and the rock-salt block in the codoped Y1-xCaxBa2-yLayCu3Oz system is calculated according to the "block model". • A new parameter γ describing the combined effects of the combinative energy (lattice degree of freedom) and the charge carrier density (charge degree of freedom) is defined. • The tendency of γ changing with doping is well consistent with that of the superconducting transition temperature (Tc) over the whole doping range, suggesting the important roles of both the lattice and charge degrees of freedom in influencing the unconventional superconductivity. Polycrystalline samples of Y 1- x Ca x Ba 2- y La y Cu 3 O z cuprate superconductors with both x and y ranging from 0 to 0.5 were investigated. The combinative energy between the perovskite block and the rock-salt block in this codoped system was calculated according to a previously proposed "block model". By defining a new parameter γ describing the combined effects of the combinative energy (lattice degree of freedom) and the charge carrier density (charge degree of freedom), it is revealed that the tendency of γ changing with doping is well consistent with that of the superconducting transition temperature (T c) over the whole doping range, suggesting the important roles of both the lattice and charge degrees of freedom in influencing the unconventional superconductivity. [ABSTRACT FROM AUTHOR]