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Break-junction tunneling on MgB2

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, *DL ~ 7.2 meV, close to the expected BC...

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Bibliographic Details
Published in:Physica. C, Superconductivity Superconductivity, 2003-03, Vol.385 (1-2), p.221-232
Main Authors: Schmidt, H., Zasadzinski, J.F., Gray, K.E., Hinks, D.G.
Format: Article
Language:English
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Summary: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, *DL ~ 7.2 meV, close to the expected BCS value, and a small gap, *DS ~ 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 *DS dominates the spectra. In these cases, a subtle feature is observed near *DS + *DL that is reminiscent of strong-coupling effects. This feature is consistent with quasiparticle scattering contributions to the interband
ISSN:0921-4534
DOI:10.1016/S0921-4534(02)02317-1