OXYGEN DEFICIENCY DEPENDENCE OF TRANSITION-TEMPERATURE IN (SM,ER)BA2CU3O7-DELTA SUPERCONDUCTORS

We have investigated the effects of oxygen deficiency (delta) on the t ransition temperature (T-c) of (Sm, Er)Ba2Cu3O7-delta superconductors by incorporating the effects of the two dimensional (2D) acoustic phon ons and plasmons in the framework of strong coupling theory. The propo sed approach for yttrium cuprates properly takes care of the double Cu O2 plane in a unit cell and has been found earlier to be successful in describing the pairing mechanism as well as the variation of T-c with delta in YBa2Cu3O7-delta system. The coupling strength (lambda), the screening parameter (mu) and the two dimensional acoustic phonon (pla smon) energy h omega(-)(omega(+)) as a function of oxygen deficiency i s worked out. Finally, the transition temperature is evaluated and is found to be consistent with the earlier experimental data on yttrium c uprates. Thus, coupled phonon-plasmon mechanism is adequate to underst and the nature of pairing mechanism and oxygen deficiency dependence o f transition temperature in 90 K (Sm,Er)Ba2Cu3O7-delta superconductors .