Considering Born–Mayer–Huggins potential as a most suitable potential to study the dynamical properties of high-temperature superconductors (HTS), the many-body quantum dynamics to obtain phonon Green’s functions has been developed via a Hamiltonian that incorporates the contributions of harmonic electron and phonon fields, phonon field anharmonicities, defects and electron–phonon interactions without considering BCS structure. This enables one to develop the quasiparticle renormalized frequency dispersion in the representative high-temperature cuprate superconductor YBa2Cu3O[Formula: see text]. The superconducting gap shows substantial changes with increased doping. The in-plane gap study revealed a [Formula: see text]-shape gap with a nodal point along [Formula: see text] direction for optimum doping ([Formula: see text] = 0.16) and the nodal point vanished in underdoped and overdoped regimes. The d[Formula: see text] pairing symmetry is observed at optimum doping with the presence of s or d[Formula: see text] components ([Formula: see text] 3%) in underdoped and overdoped regimes.
Accurate theoretical fits to laser-excited photoemission spectra in the normal phase of high-temperature superconductors
