Point-contact spectroscopy of tantalum, molybdenum, and tungsten

TL;DR

This study uses point-contact spectroscopy to analyze electron-phonon interactions in tantalum, molybdenum, and tungsten, comparing experimental spectra with theoretical models and discussing discrepancies in observed intensities and coupling constants.

Contribution

It provides experimental spectra of electron-phonon interactions in Ta, Mo, and W and compares them with theoretical models, highlighting discrepancies especially for tungsten.

Findings

Close agreement for Ta and Mo spectra with models

Discrepancy in W spectra showing blurred peaks

Measured electron-phonon coupling constants are lower than expected

Abstract

Electron-phonon interaction in superconducting transition metals (Ta, Mo, W) is investigated by the method of point-contact spectroscopy. The spectra obtained are compared with model densities of the phonon states $F(\omega)$ computed from experiments on neutron scattering, and with the tunnel electron-phonon interaction function $g(\omega)$ for Ta. Close agreement between the appropriate spectra is obtained for Ta and Mo, while a significant discrepancy is observed for W, which is the appearance of a blurred maximum instead of the two expected separated peaks on the point-contact spectra. The absolute intensities of a number of point-contact spectra $G(eV)$ and electron-phonon coupling constants $\lambda$ are calculated. For all three metals the values obtained turned out to be considerably below those expected. The possible reasons for this disagreement are discussed.