A COMBINED MECHANISM MEDIATED BY LOCHONS AND PHONONS FOR CUPRATE SUPERCONDUCTORS

We present a brief review of the combined pairing mechanism mediated b y phonons and lochons (local charged bosons) for the high temperature superconducting materials (mainly cuprates). The phonon contribution ( lambda p) being weak, the lochon part (lambda(l)) dominates to give hi gher critical temperatures (T-c). The combined mechanism along with th e variation of lambda(l) with carrier concentration (x(c)) gives the r ight variation of T-c and the oxygen isotope exponent on doping. The s uperconducting gap Delta(0) at T = 0, its ratio with T-c, the condensa tion energy, gap anisotropy, pseudogap, etc. are also discussed. With reasonable agreement with available experimental data, the combined me chanism emerges as a strong contender for an acceptable model for oxid e superconducting materials.