Role of Phonons in Superconductivity

Though the phonon mediated electron-electron interaction has been widely accepted as the cause of superconductivity, yet some doubts have been raised on the basis of the fact that many properties of superconductors are explained by employing a single Einstein frequency without taking a proper account of phonons in the superconductor. In order to check the role of phonons in superconductivity, we involve the whole of the phonon spectra for obtaining superconducting state parameters of seven superconductors, namely Mg, Zn, Be, Cd, A1, T1 and Pb in anisotropic as well as in isotropic phonon models. It has been observed that the electronphonon coupling strengthλ and the transition temperatureT c exhibit strong directional dependence and are sensitive to the phonons, reaffirming that the phonon mechanism is responsible for superconductivity. The computed values of isotope effect exponentα and the interaction strengthN0V also show similar trend, supporting the phonon mechanism.