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

A Ba1-xKxBiO3 (BKBO) grain boundary junction formed on a MgO bicrystal subs trate showed a superconductor-insulator-superconductor (SIS) behavior with a sharp gap structure and a Josephson current. A 270 GHz millimeter wave mi xing in a BKBO junction was performed by using the quasi optical technique. A log-periodic antenna, a hyperhemispherical MgO lens and a Tenon lens wer e used in order to improve coupling for millimeter wave. The IF outputs hav e some peaks depending on the photon assisted tunneling steps. This is the first time that quasiparticle mixing could be done in an oxide superconduct or.