Author(s)

G. P. Malik^1,2

¹School of Environmental Sciences, Jawaharlal Nehru University, New Delhi, India.
²Present Address: B-208 Sushant Lok 1, Gurgaon 122009, Haryana, India.

Guided by the belief that Fermi energy E_F (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 (T_cs) of both elemental and composite SCs. The μ-dependent interaction parameters consistent with the values of Δs and T_cs of any of these SCs were shown to lead to expressions for the effective mass of electrons (m^*) and their number density (n_s), critical velocity (v₀), and the critical current density j₀ at T = 0 in terms of the following five parameters: Debye temperature, E_F, 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 Ba_0.6K_0.4Fe₂As₂ (BaAs). Some of the main attributes of this SC are: it is characterized by -wave superconductivity and multiple gaps between 0 - 12 meV; its T_c ~ 37 K, but the maximum T_c of SCs in its class can exceed 50 K; E_F/kT_c = 4.4 (k = Boltzmann constant), and its T_c 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^*, n_s, v_o, and coherence length. Finally, we also deal with the issue of the stage BaAs occupies in the BCS-Bose-Einstein Condensation crossover.

Iron-Based Superconductors, Multiple Gaps, Tcs, and Other Properties of Ba_0.6K_0.4Fe₂As₂, GBCSEs, Fermi energy, BCS-BEC Crossover

Malik, G. (2017) On the s^±-Wave Superconductivity in the Iron-Based Superconductors: A Perspective Based on a Detailed Study of Ba_0.6K_0.4Fe₂As₂ via the Generalized-Bardeen-Cooper-Schrieffer Equations Incorporating Fermi Energy. Open Journal of Composite Materials, 7, 130-145. doi: 10.4236/ojcm.2017.73008.