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Transport properties of asymmetric parallel quantum dot system coupled to superconducting leads due to Andreev reflections have been studied in Coulomb blockade regime by using Non-Equilibrium Green Function technique. Andreev Transmission Probability and Josephson supercurrent (I-V characteristics) by virtue of resonant Cooper pair tunneling, a manifestation of Josephson effect, have been calculated. Superconducting order parameter, a key parameter in hybrid superconductor - quantum dot devices, regulates the Josephson Cooper pair tunneling and Fano resonance by virtue of quantum interference phenomena in asymmetric parallel quantum dot system. It has been found that superconducting order parameter first enhances and then suppresses the Cooper pair tunneling while Fano resonance gets completely suppressed. Complete disappearance of Fano effect signifies the dominance of superconducting order parameter over Fano effect in asymmetric parallel quantum dot system coupled to conventional superconducting leads. [ABSTRACT FROM AUTHOR]

We performed first principle study of electronic and optical properties of triangular silicene nano flakes passivated with H, F and Cl atoms. A large variation of charge density in Halogen passivations results into decrease of HOMO-LUMO gap from 1.02 eV to ∼0.80 eV. Also the red shift of structure peaks in imaginary dielectric function compared to hydrogen passivated flake, which represents electronic transitions, were observed for halogen passivations. Peaks in EEL functions representing plasmons were also red shifted for halogen passivations. Therefore, passivation by different atoms indicates tuning of electronic and optical properties of quantum dots for opto-electronic devices. [ABSTRACT FROM AUTHOR]