Point-contact spectroscopy of MgB2
Résumé
Point-contact spectroscopy measurements on magnesium diboride reveal the existence of two superconducting energy gaps closing at the same transition temperature in line with the multi-band model of superconductivity. The sizes of the two gaps (Dp ¼ 2:8 meV and Dr ¼ 6:5-7 meV) are respectively smaller and larger than the expected weak coupling value of the one-gap superconductor. The smaller gap is rapidly filled by a small magnetic field of about 1-2 T much lower than the real upper critical field Hc2. The larger gap is closed at the anisotropic Hc2. Above the gap energies reproducible non-linearities are observed at the characteristic phonon energies of MgB2.