A Combined Mechanism Mediated by Lochons and Phonons for Cuprate Superconductors

Abstract

We present a brief review of the combined pairing mechanism mediated by phonons and lochons (local charged bosons) for the high temperature superconducting materials (mainly cuprates). The phonon contribution (λ p ) being weak, the lochon part (λl) dominates to give higher critical temperatures (T c ). The combined mechanism along with the variation of λl with carrier concentration (x c ) gives the right variation of T c and the oxygen isotope exponent on doping. The superconducting gap Δ(0) at T = 0, its ratio with T c , the condensation energy, gap anisotropy, pseudogap, etc. are also discussed. With reasonable agreement with available experimental data, the combined mechanism emerges as a strong contender for an acceptable model for oxide superconducting materials.