Carrier-Concentration-Dependent Superconductivity in SnTe and GeTe

A theoretical calculation is given of the dependence of the superconducting transition temperature on carrier concentration for the many-valley semiconductors SnTe and GeTe. The model used includes an accurate description of all intravalley processes; however, intravalley interactions alone are inadequate to explain the superconductivity of these materials. This contradicts the results of a recent model calculation of Hulm et al. which involved only intravalley interactions. Intervalley phonon-induced interactions are found to be the dominant mechanism. Good agreement with the available data over the entire range of carrier concentration is found by adjusting a single parameter, the intervalley deformation potential.