Andreev tunneling assisted suppression of Fano resonance in asymmetric parallel quantum dot system coupled to superconducting leads

摘要

Electronic transport through asymmetrically parallel coupled quantum dot system hybridized between conventional superconducting leads has been investigated theoretically in the Coulomb blockade regime by using Non-Equilibrium Green Function formalism. For resonant Cooper pair tunneling, the Andreev transmission probability and Josephson supercurrent (I - V characteristics) have been presented for each configuration of coupled quantum dot system and for transition of coupled quantum dot system from series to symmetric parallel configuration. Superconducting order parameter regulates the Josephson Cooper pair tunneling in such a way that it initially enhances and then suppresses the resonant Cooper pair tunneling when system is tuned from series to symmetric parallel configuration. Furthermore, it has been found that the Fano effect, reported in asymmetric parallel configuration of CQD system, gets completely suppressed by Andreev tunneling for a particular value of superconducting order parameter and lead-dot coupling strength.