Temperature and field dependence of the energy gap of MgB2/Pb planar junctions -: art. no. 184516

We have constructed MgB2/Pb planar junctions for both temperature and field dependence studies. Our results show that the small gap is a true bulk property of MgB2 superconductor, not due to surface effects. The temperature dependence of the energy gap manifests a nearly BCS-like behavior. Analysis of the effect of magnetic field on junctions suggests that the energy gap of MgB2 depends nonlinearly on the magnetic field. Moreover, MgB2 has an upper critical field of 15 T, in agreement with some reported H-c2 from transport measurements.