On the Properties of Elemental and High-<i>T</i><i><sub>c</sub></i> Superconductors in a Unified Framework I

For both elemental and high-Tc superconductors (SCs), we show that the empirical values of their Tc, gaps (Δs) and coherence lengths (ξs)—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-Tc 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 = Tc and 0 K, corresponding to the Tcs, Δs and ξs of these SCs, The other 12 SCs dealt with here are Al, Sn, Nb, Cd, Pb, MgB2, YBCO, Bi-2212, Tl-2212, Tl-2223 and compressed H3S and LaH10.