Mesoscopic transport through a hybrid system with toroidal carbon nanotube coupled to normal and superconducting leads

Abstract

The coherent transport through toroidal carbon nanotubes (TCN) coupled with normal metal and superconductor is investigated by employing the nonequilibrium Green's function technique. TCN is threaded with a static magnetic flux φ which induces Aharonov–Bohm-like and Zeeman effects. The conductance and tunneling current are evaluated to show the resonant and oscillating behaviors associated with φ. The energy gaps Δ and E g of superconductor and TCN take effect in electron transport. The Andreev reflection produces novel tunneling behaviors, since it provides new channels for electron to tunnel. Due to the metal–semiconductor transition with respect to φ, the coherent transport intimately relies on the structure of TCN. The density of state (DOS) of superconductor has its contribution to the tunneling in whole energy region.