Shot noise in a superconducting hybrid molecular device

We derive a general expression for the current noise for an 'N-QD-S' system by using the non-equilibrium Green's function approach. We apply our formula to investigate the shot noise of a finite carbon nanotube sandwiched by a normal metal electrode and a superconducting electrode. By adjusting the gate voltage, the transparency of the system can be changed substantially and the Fano factor can be tuned from zero to nearly one. For asymmetric coupling, the Fano factor with a small gate voltage versus the bias voltage gives an anomalous peak around zero bias voltage.