Heterocontact Effects in Point Contact Electron-Phonon Spectroscopy of the Alkali Metals.

For a small contact between two different materials a heterocontact, we derive the free electron expression for the electron-phonon spectral function determined from the measured I-V characteristic. The heterocontact spectral function differs strikingly from the homocontact spectral function in that it excludes scattering through angles less than a minimum angle in the larger bandwidth material. We calculate realistic heterocontact spectra for pairs of alkali metals. If in a given pair of alkalis the smaller bandwidth material is replaced by one with a still smaller bandwidth, the size of the signal from the larger bandwidth material decreases sometimes dramatically, and the part of the spectrum due to scattering by 2k sub F phonons is relatively enhanced. Author