Tunneling characteristics in epitaxial MgB2 tunnel junctions with amorphous and epitaxial tunnel barriers

Abstract

Superconductor (S) tunneling in the novel two-band superconductor magnesium diboride (MgB2) has been investigated with a view exploring MgB 2 by using spin-polarized tunneling and developing MgB2 Josephson devices. Besides quasiparticle tunneling into MgB2, MgB2 / Insulator (I) / MgB2 Josephson junctions have been fabricated, all in situ, on Si single-crystal substrates. Two superconducting energy gaps have been determined unequivocally by planar S/I/S tunneling. Our results have shown the Josephson effect in all MgB2 epitaxial tunnel junctions.