A New Method of Probing the Phonon Mechanism in Superconductors including MgB$_{2}$

摘要

Weak localization has a strong influence on both the normal andsuperconducting properties of metals. In particular, since weak localizationleads to the decoupling of electrons and phonons, the temperature dependence ofresistance (i.e., $\lambda_{tr}$) is decreasing with increasing disorder, asmanifested by Mooij's empirical rule. In addition, Testardi's universalcorrelation of $T_{c}$ (i.e., $\lambda$) and the resistance ratio (i.e.,$\lambda_{tr}$) follows. This understanding provides a new means to probe thephonon mechanism in superconductors including MgB$_{2}$. The merits of thismethod are its applicability to any superconductors and its reliability becausethe McMillan's electron-phonon coupling constant $\lambda$ and $\lambda_{tr}$change in a broad range, from finite values to zero, due to weak localization.Karkin et al's preliminary data of irradiated MgB$_{2}$ show the Testardicorrelation, indicating that the dominant pairing mechanism in MgB$_{2}$ is thephonon-mediated interaction.