|Title||Elaboration of the alpha-model derived from the BCS theory of superconductivity|
|Publication Type||Journal Article|
|Year of Publication||2013|
|Type of Article||Article|
s constant and T-c is the superconducting transition temperature. On the other hand, to calculate the electronic free energy, entropy, heat capacity and thermodynamic critical field versus T, the alpha-model takes alpha to be an adjustable parameter. Here we write the BCS equations and limiting behaviors for the superconducting state thermodynamic properties explicitly in terms of alpha, as needed for calculations within the alpha-model, and present plots of the results versus T and alpha that are compared with the respective BCS predictions. Mechanisms such as gap anisotropy and strong coupling that can cause deviations of the thermodynamics from the BCS predictions, especially the heat capacity jump at T-c, are considered. Extensions of the alpha-model that have appeared in the literature, such as the two-band model, are also discussed. Tables of values of Delta(T)/Delta(0), the normalized London parameter Lambda(T)/Lambda(0) and lambda(L)(T)/lambda(L)(0) calculated from the BCS theory using alpha = alpha(BCS) are provided, which are the same in the alpha-model by assumption. Tables of values of the entropy, heat capacity and thermodynamic critical field versus T for seven values of alpha, including alpha(BCS), are also presented.
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