The roles of potential symmetry in transport properties of superconducting quantum point contacts

Abstract

We present a theoretical transport analysis for a hybrid quantum point contact which consists of a quantum dot connected to two superconducting reservoir electrodes. The analysis focuses on the effects of symmetry of the potential drops across the device on the transport properties of the system. Common beliefs normally presume the potential drops to be trivial for such systems, henceforth the analysis is often based on perfect symmetry assumption. In contrary, we predicted that the details of potential drops have very significant effects in the current-voltage (I-V) characteristics of the system. This is because slight perturbations on the symmetry of potential drops can dramatically alter the transport characteristics, both in linear and non-linear regimes. Particularly when the coupling strengths between the quantum dot and the leads are weak, the system exhibits ultra-high sensitivity with respect to potential symmetry variations, and this phenomenon turns out to be robust regardless of the coupling strength asymmetry. Copyright © 2010 American Scientific Publishers.