Abstract
We address the Tc (s) and multiple gaps of La2CuO4 (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 YBa2Cu3O6.6 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-Tc ratio (2Δ0/kBTc), 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 × 1021 - 5.6 × 1021 cm-3, and values of 0.27 - 0.29 and 1.12 for the gap-to-Tc ratios of the smaller gaps.
Highlights
It is well known that La2CuO4 (LCO) is an insulator
On doing so we find that it is characterized by layers [11] of LaO, OLa, and CuO2. This implies that if La is the lower of the two bobs of the double pendulum in the layers that comprise one of the sub-lattices, it is the upper bob in the layers of the other sub-lattice. This feature brings into play two Debye temperatures, in the application of Two-Phonon Exchange Mechanism (TPEM) to LCO as for any of the other HTSCs, but only one interaction parameter because it is the same species of ions in both the sub-lattices that causes pairing
By including μ in GBCSEs as applicable to LCO, appealing to an idea inspired by the work of Tacon et al [9] and using as input any of the observed values of the gap-to-Tc ratio for 36 ≤ Tc ≤ 40 K, we have been led to solutions for μ and λ that are “sensible”
Summary
It is well known that La2CuO4 (LCO) is an insulator. It becomes superconducting when suitably doped,. The work reported here is motivated by the need to: a) Bring the understanding of LCO in the framework of GBCSEs at par with that of all the other HTSCs noted above This is done where for any Tc in the range 37 - 40 K, it is shown, in accord with experiment, that 2∆20/kBTc = 4.3, where kB is the Boltzmann constant, and b) Explain experimental values for the gap-to-Tc ratio other than 4.3, i.e., 7.1, ≈8 and 9.3, attention to which was drawn by Bednorz and Müller [6] in their Nobel lecture. The final section is devoted to a discussion of our findings
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
