Role of interband scattering in neutron irradiated MgB2 thin films by scanning tunneling spectroscopy measurements

A series of MgB2 thin films systematically disordered by neutron irradiation have been studied by scanning tunneling spectroscopy. The c-axis orientation of the films allowed a reliable determination of the local density of states of the pi band. With increasing disorder, the conductance peak moves towards higher voltages and becomes lower and broader, indicating a monotonic increase of the pi gap and of the broadening parameter. These results are discussed in the framework of two-band superconductivity.