Abstract
The paper analyzes the influence of the hole density, the out-of-plane or in-plane disorder, and the isotopic oxygen mass on the zero temperature energy gap (2Δ(0))Y1-xCaxBa2Cu1-yZny3O7-δ(YCBCZO) andLa1.96-xSrxHo0.04CuO4(LSHCO) superconductors. It has been found that the energy gap is visibly correlated with the value of the pseudogap temperature (T⋆). On the other hand, no correlation between 2Δ(0) and the critical temperature (TC) has been found. The above results mean that the value of the dimensionless ratio2Δ0/kBTCcan vary very strongly together with the chemical composition, while the parameter2Δ(0)/kBT⋆does not change significantly. In the paper, the analytical formula which binds the zero temperature energy gap and the pseudogap temperature has been also presented.
Highlights
The thermodynamics of the high-temperature superconducting state in cuprates differs significantly from the thermodynamics predicted in the framework of the classical BCS theory [4,5,6,7]
In addition to the too high value of the critical temperature, the most important difference seems to be in the existence of the second characteristic temperature, which is called the pseudogap temperature (T⋆)
It is believed that the critical temperature in cuprates sets the maximum value of T, at which disappears the coherence of the superconducting state, while T⋆ determines the temperature, in which the energy gap (2Δ) ceases to exist at the Fermi level [8]
Summary
The thermodynamics of the high-temperature superconducting state in cuprates differs significantly from the thermodynamics predicted in the framework of the classical BCS theory [4,5,6,7]. We have determined a full dependence of the order parameter on temperature for the YCBCZO and LSHCO superconductors.
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