Intraband vs. interband scattering rate effects in neutron irradiated MgB₂

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: 10 January 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, , 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, 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 (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.