Abstract
Guided by the belief that Fermi energy EF (equivalently, chemical potential μ) plays a pivotal role in determining the properties of superconductors (SCs), we have recently derived μ-incorporated Generalized-Bardeen-Cooper-Schrieffer equations (GBCSEs) for the gaps (Δs) and critical temperatures (Tcs) of both elemental and composite SCs. The μ-dependent interaction parameters consistent with the values of Δs and Tcs of any of these SCs were shown to lead to expressions for the effective mass of electrons (m*) and their number density (ns), critical velocity (v0), and the critical current density j0 at T = 0 in terms of the following five parameters: Debye temperature, EF, a dimensionless construct y, the specific heat constant, and the gram-atomic volume. We could then fix the value of μ in any SC by appealing to the experimental value of its j0 and calculate the other parameters. This approach was followed for a variety of SCs—elemental, MgB2 and cuprates and, with a more accurate equation to determine y, for Nitrogen Nitride (NbN). Employing the framework given for NbN, we present here a detailed study of Ba0.6K0.4Fe2As2 (BaAs). Some of the main attributes of this SC are: it is characterized by -wave superconductivity and multiple gaps between 0 - 12 meV; its Tc ~ 37 K, but the maximum Tc of SCs in its class can exceed 50 K; EF/kTc = 4.4 (k = Boltzmann constant), and its Tc plotted against a tuning variable has a dome-like structure. After drawing attention to the fact that the -wave is an inbuilt feature of GBCSEs, we give a quantitative account of its several other features, which include the values of m*, ns, vo, and coherence length. Finally, we also deal with the issue of the stage BaAs occupies in the BCS-Bose-Einstein Condensation crossover.
Highlights
Ever since their discovery in 2008 by Kamihara et al [1], the iron-based superconductors (FeSCs) characterized by multiple gaps (Δs) and high-Tcs have been avidly investigated both experimentally and theoretically
Guided by the belief that Fermi energy EF plays a pivotal role in determining the properties of superconductors (SCs), we have recently derived μ-incorporated Generalized-Bardeen-Cooper-Schrieffer equations (GBCSEs) for the gaps (Δs) and critical temperatures (Tcs) of both elemental and composite SCs
We propose in this note to show that many properties of FeSCs are explicable quantitatively via another approach which is based on a generalization of the one-band Bardeen-Cooper-Schrieffer equations (GBCSEs) in the meanfield approximation
Summary
Ever since their discovery in 2008 by Kamihara et al [1], the iron-based superconductors (FeSCs) characterized by multiple gaps (Δs) and high-Tcs have been avidly investigated both experimentally and theoretically. We propose in this note to show that many properties of FeSCs are explicable quantitatively via another approach which is based on a generalization of the one-band Bardeen-Cooper-Schrieffer equations (GBCSEs) in the meanfield approximation. Since such a proposal may prima facie seem as bizarre, there seems a need at the outset to make it physically plausible that the approach based on GBCSEs may, at least, play a valuable role in supplementing the conventional multi-band approach.
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