Point-contact spectroscopy in copper: temperature measurements. Dependence of point-contact spectra on contact parameters

Measurements of the temperature dependence of the point-contact resistance R(T) are used to determine the effective contact size d and the mean free path li of an electron in the neighborhood of the contact. The dependence of the parameters of point-contact spectra on li and d is studied. The experimental results are compared with the predictions of a theoretical model for reabsorption of nonequilibrium phonons. This allows the temperature of the nonequilibrium phonons to be estimated (near the L peak the temperature is about 70–80 °K). The observed dependence R(T) ∼T4 for 20 < T <40°K is explained by single-phonon Umklapp processes, which make the greatest contribution to the point-contact spectrum of copper.

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