A Study of Superconducting La₂CuO₄ via Generalized BCS Equations Incorporating Chemical Potential

Abstract

We address the T c ( s ) and multiple gaps of La 2 CuO 4 (LCO) via generalized BCS equations incorporating chemical potential. Appealing to the structure of the unit cell of LCO, which comprises sub- lattices with LaO and OLa layers and brings into play two Debye temperatures, the concept of itinerancy of electrons, and an insight provided by Tacon et al.’s recent experimental work concerned with YBa 2 Cu 3 O 6.6 which reveals that very large electron-phonon coupling can occur in a very narrow region of phonon wavelengths, we are enabled to account for all values of its gap-to- T c ratio (2Δ 0 /k B T c ), i.e., 4.3, 7.1, ≈8 and 9.3, which were reported by Bednorz and Müller in their Nobel lecture. Our study predicts carrier concentrations corresponding to these gap values to lie in the range 1.3 × 10 21 - 5.6 × 10 21 cm -3 , and values of 0.27 - 0.29 and 1.12 for the gap-to- T c ratios of the smaller gaps.