TITLE:
On the s±-Wave Superconductivity in the Iron-Based Superconductors: A Perspective Based on a Detailed Study of Ba0.6K0.4Fe2As2 via the Generalized-Bardeen-Cooper-Schrieffer Equations Incorporating Fermi Energy
AUTHORS:
G. P. Malik
KEYWORDS:
Iron-Based Superconductors, Multiple Gaps, Tcs, and Other Properties of Ba0.6K0.4Fe2As2, GBCSEs, Fermi energy, BCS-BEC Crossover
JOURNAL NAME:
Open Journal of Composite Materials,
Vol.7 No.3,
July
7,
2017
ABSTRACT: Guided by the belief that Fermi energy EF (equivalently,
chemical potential μ) plays a pivotalrole in determining the
properties of superconductors (SCs), we have recently derived μ-incorporated
Generalized-Bardeen-Cooper-Schriefferequations (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,
andcoherence length. Finally, we also deal with the issue of the stage BaAs
occupies in the BCS-Bose-Einstein Condensation crossover.