Density of states and phonon spectrum of superconducting thallium by electron tunnelling

Publisher Website
Google Scholar
Abstract
We discuss the application of electron tunnelling to the study of super conductors and describe the results of tunnelling experiments involving superconducting thallium. We show that by measuring the first and second derivatives of the tunnel junction characteristics it is possible to determine the superconducting density-of-states variation in thallium and to draw some conclusions about the shape of its phonon spectrum. The principle peaks in the phonon spectrum (corresponding to the transverse and longitudinal modes) are found to occur at 40 mev and 945 mev, respectively. The end of the phonon spectrum appears to be located at 106 mev and evidence for this and other critical points is presented in this paper. The average value of the full gap for thallium was found to be 2Δ(0)Tl = (0.74±0.02) mev (i.e. 2Δ(0)Tl = (3.55±0.1) kTc) although considerable anisotropy of the gap was observed. Values of 2Δ(Tl) ranging from 059 mev to at least 097 mev, and possibly 129 mev, were measured.

This publication has 16 references indexed in Scilit: