Gap measurements in MgB2 break-junction and point-contact heterostructures: test of the two-band models

We present a series of results concerning the determination of the gap(s) in MgB2 by means of break-junction and point-contact measurements. We were able to observe the small 3D gap predicted by the two-band models for MgB2 in the clean limit as well as the gap in dirty limit. We were also able to follow the temperature evolution of the latter, from 4.2 K up to a reduced critical temperature. We show that all our results can be explained in the framework of the two-band model provided that the existence of a damaged surface in dirty limit proximized by the clean bulk as well as the occurrence of parallel contacts are admitted.