Pairing mechanism and superconducting state parameters in YBa2Cu3O delta

The nature of pairing mechanism and the superconducting state of bi-layer o ptimised hole doped Yttrium based cuprates have been theoretically investig ated using the strong coupling theory. An interaction potential is set up w hich incorporates various interactions as hole-hole, hole-phonon and hole-p lasmon with proper layered structure of the system. For the admissible valu e of interlayer phonons the deduced value of coupling strength favours the strong coupling regime and screening parameter infers the effective screeni ng of holes as carriers. The transition temperature with the use of model c oupling parameters is estimated as T-c(Ph) = 73.45 K. Incorporating the 2-D acoustic plasmons the T,, enhances to 90 K, which is in the measured range . The approach is further applied Co evaluate the isotope exponent and the reduced total isotope exponent suggests a transition from phonon mediated s uperconductivity to dual phonon-electronic boson mechanism in high-T-c Yttr ium based systems. The energy gap ratio is substantially larger than BCS ra tio and infers that the strong coupling effects are important. The implicat ions of the cc-operative phonon-plasmon approach are discussed.