Microcontact spectroscopy of tantalum, molybdenum, and tungsten

Electron–phonon interaction in superconducting transition metals (Ta, Mo, W) is investigated by the method of microcontact spectroscopy. The spectra obtained are compared with model densities of the phonon states F(ω) computed from experiments on neutron scattering, and with the tunnel Electron–phonon interaction function g(ω) 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 microcontact spectra. The absolute intensities of a number of microcontact spectra G(eV) and electron–phonon coupling constants λ 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.

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