Eliashberg Spectral Functions for Some High-Tc Superconductors

We used a simplified but more realistic form of a model spectral functions for some high-Tc superconductors (e.g., LSCO, YBCO, BSCCO), avoiding the elaborate process of solving the Eliashberg equations numerically. The resulting spectral functions, constructed using the phonon density of states (PDOS), obtained from INS experiments with the easy use of available expressions, reproduce the observed critical temperature, gap ratio, and several other parameters. Tc is found to have a stronger increase with the electron–phonon coupling constant λ compared to those obtained from several equations, constructed from numerical solution of the Eliashberg equations for lower λ values. The obtained functions show widely spreading spectra that inhibit lattice instability by yielding not too large values of λ (< 2.95).