The electron-phonon interaction in single crystals was investigated by point-contact spectroscopy. For the first time the electron coupling with E2g phonon modes was resolved in the point-contact spectra. The correlation between intensity of the extremely broad E2g modes in the point-contact spectra and value of the superconducting gap was established. The observations favored current theoretical models for electron-phonon mediated superconductivity in MgB2, and they matched the harmonic phonon model better.

Search for E(2g) Phonon Modes in MgB2 Single Crystals by Point-Contact Spectroscopy. Y.G.Naidyuk, I.K.Yanson, O.E.Kvitnitskaya, S.Lee, S.Tajima: Physical Review Letters, 2003, 90[19], 197001 (3pp)