Quasiparticle mixing in Ba-K-Bi-O grain boundary junctions

A Ba/sub 1-x/K/sub x/BiO/sub 3/ (BKBO) grain boundary junction formed on a MgO bicrystal substrate showed a superconductor-insulator-superconductor (SIS) behavior with a sharp gap structure and a Josephson current. A 270 GHz millimeter wave mixing in a BKBO junction was performed by using the quasi optical technique. A log-periodic antenna, a hyperhemispherical MgO lens and a Teflon lens were used in order to improve coupling for millimeter wave. The IF outputs have some peaks depending on the photon assisted tunneling steps. This is the first time that quasi-particle mixing could be done in an oxide superconductor.