Study of the Josephson Current of ${\rm MgB}_{2}/{\rm Insulator/Pb}$ Tunnel Junctions

Abstract

We have fabricated MgB 2 Insulator Pb Josephson tunnel junctions on MgB 2 films deposited by hybrid physical-chemical vapor deposition using native oxide as the tunnel barrier. For the critical current of the junction onMgB 2 (0001) film, its temperature dependence follows the Ambegaokar-Baratoff relation and its magnetic field dependence exhibits a Fraunhofer pattern. From analysing the magnetic field dependence of the critical current of the junction on -axis tilted MgB 2 film, we find small contribution of the Josephson current from the -plane tunneling, which may suggest a phase difference between the order parameters of MgB 2 and bands.