Superconductivity and Lattice Dynamics of White Tin

Abstract

We present the results of a tunneling investigation and the details of the electron-phonon interaction in superconducting tin. From an iterative solution of the Eliashberg gap equations, the phonon spectrum, weighted by the square of the electron-phonon coupling constant, is determined. Comparison of this result with neutron scattering data suggests that, as in Pb, off-symmetry directions must be considered carefully in any determination of the tin phonon spectrum. The resolution and reproducibility of the tunneling technique is discussed at some length; in particular, we show that the Coulomb pseudopotential ${\mu }^{*}$ is extremely sensitive to small experimental errors. We suggest that a value of ${\mu }^{*}$ near the theoretical value of 0.10 can be taken as an indication of acceptably accurate experimental measurements.