In strong-coupling superconductors with a short electron mean free path the self-energy effects in the superconducting order parameter play a major role in the phonon manifestation of the point-contact spectra at the above-gap energies. We derive asymptotic expressions for the nonlinear conductivity of tunnel, ballistic, and diffusive point contacts in the case eV>>Delta, and show that these expressions not only qualitatively, but also semiquantitatively correspond to the measurements of the phonon structure in the point-contact spectra for the pi band of MgB2 thin films.
|Journal||Physical Review B (Condensed Matter and Materials Physics)|
|Publication status||Published - 2004|
Yanson, I. K., Beloborod'ko, S. I., Naidyuk, Y. G., Dolgov, O. V., & Golubov, A. A. (2004). Phonon self-energy effects in the superconducting energy gap of MgB2 point-contact spectra. Physical Review B (Condensed Matter and Materials Physics), 69(10), 100501-. https://doi.org/10.1103/PhysRevB.69.100501