T W Heitmann et al 2004 Supercond. Sci. Technol. 17 237 doi:10.1088/0953-2048/17/2/001
T W Heitmann1,2, S D Bu3, D M Kim3, J H Choi3, J Giencke3, C B Eom1,2,3, K A Regan4, N Rogado4, M A Hayward4, T He4, J S Slusky4, P Khalifah4, M Haas4, R J Cava4, D C Larbalestier2,3 and M S Rzchowski1,2
Show affiliationsWe report scanning tunnelling spectroscopy (STS) measurements of the gap properties of both ceramic MgB2 and c-axis oriented epitaxial MgB2 thin films. Both show a temperature dependent zero bias conductance peak and evidence for two superconducting gaps. We report tunnelling spectroscopy of superconductor–insulator–superconductor (S-I-S) junctions formed in two ways in addition to normal metal–insulator–superconductor (N-I-S) junctions. We find a gap Δ = 2.2–2.8 meV, with spectral features and temperature dependence that are consistent between S-I-S junction types. In addition, we observe evidence of a second, larger gap, Δ = 7.2 meV, consistent with a proposed two-band model.
74.45.+c Proximity effects; Andreev effect; SN and SNS junctions
74.25.Fy Transport properties (electric and thermal conductivity, thermoelectric effects, etc.)
74.70.Ad Metals; alloys and binary compounds (including A15, MgB2, etc.)
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
Issue 2 (February 2004)
Received 5 September 2003, in final form 6 November 2003
Published 10 December 2003
T W Heitmann et al 2004 Supercond. Sci. Technol. 17 237
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