Electron-phonon interaction and modulation temperature spectroscopy in Cr point contacts

Nonlinearities of the current-voltage characteristics (IVC) of pressed point contacts of Cr are measured at T = 4.2 K and 77 K. For voltages corresponding to the phonon spectrum frequencies, the second derivatives of IVC’s display singularities associated with the electron-phonon interaction (EPI). The EPI spectral function, whose peak coincides with the most reliable functions of the phonon density of states and which is distinguished by an increase in the relative intensity of the low-frequency peak, is reconstructed. At low voltages, a region of decreasing differential resistance of contacts is observed and is apparently associated with the impurities introduced into the contacts at the time of their fabrication. The connection between the strong IVC nonlinearity observed for high voltages and the thermal violation of the antiferromagnetic order in the contact is based on a comparison of experimental data with the results of numerical computations of the second IVC derivative in the thermal limit.

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