Evidence for a two-band behavior of MgB2 from point-contact and tunneling spectroscopy

The break-junction tunneling has been systematically investigated in MgB2. Two types of the break-junction contacts have been exploited on the same samples, which demonstrated tunnel contact like (SIS) and point contact like (SnS) behavior. Both of them have shown the existence of the two distinct energy gaps. We have also observed peculiarities on the I(V)characteristics related to Leggett's collective mode assisted tunneling (C) 2003 Elsevier Ltd. All rights reserved.