Phys. Rev. B 71, 214502 (2005) [7 pages]Effect of disorder in MgB2 thin filmsReceived 30 July 2004; revised 24 January 2005; published 2 June 2005 We report on scanning tunneling spectroscopy studies of magnesium diboride (MgB2) thin films grown by different techniques. The films have critical temperatures ranging between 28 and 41 K with very different upper critical fields. We find that the superconducting gap associated with the σ band decreases almost linearly with decreasing critical temperature while the gap associated with the π band is only very weakly affected in the range of critical temperatures above 30 K. In the sample with the lowest critical temperature (28 K) we observe a small increase of the π gap that can only be explained in terms of an increase in the interband scattering. The tunneling data was analyzed in the framework of the two-band model. The magnetic-field-dependent tunneling spectra and the upper critical field measurements of these disordered samples can be consistently explained in terms of an increase of disorder that mostly affects the π band in samples with reduced critical temperatures. © 2005 The American Physical Society URL:
http://link.aps.org/doi/10.1103/PhysRevB.71.214502
DOI:
10.1103/PhysRevB.71.214502
PACS:
74.70.Ad, 74.50.+r, 74.25.Jb, 68.37.Ef
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