Effect of thermal phonons and two-dimensional acoustic plasmons on superconductivity in YBa 2CuO 7

Abstract

The superconducting transition temperature, T c, has been studied using the strongly coupled theory of superconductors in high- T c YBa 2Cu 3O 7 in the presence of realistic physical parameters, thermal phonons and two-dimensional acoustic plasmons. The calculated value of T c, using a realistic phonon distribution function, the electron-electron Coulomb interaction and the Stoner factor, comes out to be ≈ 65 K. When the finite temperature effect is taken into account through the modification of the temperature dependence of the electron-phonon mass enhancement factor, the value of T c increases significantly by ≈ 18 K to ≈ 83 K. Finally, when the two-dimensional acoustic plasmons are considered, a further increase of ≈ 17 K results, making the calculated T c ≈ 102 K, which is in reasonable agreement with the experimental results. The superconductivity in YBa 2Cu 3O 7 is, thus, marked by strong coupling effects, electron-phonon interaction, the finite temperature effect and electron-plasmon interaction, which contribute significantly towards its high T c.