2002/09/30 by H. Schmidt, J. F. Zasadzinski, K. E. Gray +1
Materials Science · Physics and Astronomy · #Band gap #Break junction #Condensed matter physics #Conductance #Coupling (piping) #Critical current #Iron-based superconductors research #Magnesium diboride #Materials science #Physics #Physics of Superconductivity and Magnetism #Quantum mechanics #Quantum tunnelling #Quasiparticle #Scattering #Spectral line #Superconductivity #Superconductivity in MgB2 and Alloys #cond-mat.supr-con
paper · pdf · doi:10.1016/s0921-4534(02)02317-1
published as Physica C 385 (2003) 221-232 · 9 pages, 10 pictures, accepted for publication in a special issue of Physica C on MgB2, minor changes
arxiv created 2002/11/04 · openalex publication_date 2003/01/21 · arxiv updated 2009/11/30 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
Tunneling data on magnesium diboride, MgB2, are reviewed with a particular focus on superconductor-insulator-superconductor (SIS) junctions formed by a break-junction method. The collective tunneling literature reveals two distinct energy scales, a large gap, DeltaL~7.2 meV, close to the expected BCS value, and a small gap, DeltaS~2.4 meV. The SIS break junctions show clearly that the small gap closes near the bulk critical temperature, Tc=39 K. The SIS spectra allow proximity effects to be ruled out as the cause for the small gap and therefore make a strong case that MgB2 is a coupled, two-band superconductor. While the break junctions sometimes reveal parallel contributions to the conductance from both bands, it is more often found that DeltaS dominates the spectra. In these cases, a subtle feature is observed near DeltaS+DeltaL that is reminiscent of strong-coupling effects. This feature is consistent with quasiparticle scattering contributions to the interband coupling which provides an important insight into the nature of two-band superconductivity in MgB2.