For both elemental and high- T c superconductors (SCs), we show that the empirical values of their T c , gaps (Δs) and coherence lengths ( ξ s)—which are among more than a dozen parameters that characterize an SC of each category—are explicable in a unified framework of chemical potential ( μ )-incorporated generalized BCS equations which provide an alternative to their explanation via the muti-band approach. Notable features of this study are: i) It sheds new light on the deviations of the gap-to- T c ratios of the elemental SCs from the universal value. ii) Among the SCs it deals with is Bi-2223 which has the remarkable property of being characterized by three gaps as reported by Ponomarev, et al. , (Pis’ma v ZhETF (JETP Lett.) 100,126 (2014)). iii) It employs a novel approach of simultaneously solving three or four equations which yield the value of the Fermi velocity and the values of μ and the interaction parameters in the pairing equation, both at T = T c and 0 K, corresponding to the T c s, Δs and ξ s of these SCs, The other 12 SCs dealt with here are Al, Sn, Nb, Cd, Pb, MgB 2 , YBCO, Bi-2212, Tl-2212, Tl-2223 and compressed H 3 S and LaH 10 .
KeywordsGeneralized BCS EquationsChemical PotentialCharacteristic Parameters of a Superconductor and Their Dependence on Chemical PotentialMultiple Debye Temperatures
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