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EPL, 77 (2007) 57005
DOI: 10.1209/0295-5075/77/57005

Intraband vs. interband scattering rate effects in neutron irradiated MgB2

M. Putti1, P. Brotto1, M. Monni1, E. Galleani d'Agliano1, A. Sanna2 and S. Massidda2

1  CNR-INFM-LAMIA and Dipartimento di Fisica, Università di Genova - Via Dodecaneso 33, 16146 Genova, Italy
2  CNR-INFM-SLACS and Dipartimento di Fisica, Università di Cagliari, Cittadella Universitaria, I-09124 Monserrato (CA), Italy


received 27 November 2006; accepted in final form 10 January 2007; published March 2007
published online 20 February 2007

Abstract
One of the most important predictions of the two-gap theory of superconductivity concerns the role of interband scattering (IBS) by impurities. IBS is expected to decrease the critical temperature, $T_{{\rm c}}$, of MgB2 to a saturation value of about 20 K, where the two gaps merge to a single one. These predictions have been partially contradicted by experiments. In fact, $T_{{\rm c}}$ does not saturate in irradiated samples, but decreases linearly with residual resistivity and the merging of the gaps has been observed at a much lower $T_{{\rm c}}$ (11 K). In this paper we argue that, while at low level of disorder IBS is the leading mechanism that suppresses superconductivity, at higher disorder the experimental results can only be understood if the smearing of the density of states due to intraband electron lifetime effects is considered.

PACS
74.70.Ad - Metals; alloys and binary compounds (including A15, MgB2, etc.).
61.80.Hg - Neutron radiation effects.
74.62.Dh - Effects of crystal defects, doping and substitution.

© Europhysics Letters Association 2007