STUDY OF JOSEPHSON-QUASI-PARTICLE CYCLES IN SUPERCONDUCTING SINGLE-ELECTRON TRANSISTORS

We have investigated the charge transport through superconducting single-electron transistors. With a sample which has large charging energy E(c) > Delta, where Delta is a superconducting energy gap of the electrodes, we studied the positions of the so-called Josephson-quasiparticle (JQP) peaks. We demonstrate that the JQP cycles coexist with the normal quasiparticle current even at the bias voltages above the Coulomb blockade threshold. Bias voltage conditions for observing these peaks are also classified for various parameter regions.