Optimal control of shot noise and Fano factor by external fields

A method is devised to control the current, shot noise and Fano factor in a molecular junction using external fields. The tunneling of electrons through a molecular junction weakly coupled to two leads in the presence of a time-dependent external field is studied using a quantum master equation approach. By combining optimal control theory and assuming a predefined time-dependent current pattern, an external field can be determined which does generate a current pattern close to the requested one. With this approach the current flow pattern in time can be chosen in an almost arbitrary fashion. The same technique can be applied to control the shot noise. For minimizing the current, the corresponding shot noise decreases but does not vanish. By minimizing the shot noise, the corresponding current also approaches zero for the present model of spinless electrons. Within certain limits the proposed strategy even works well for the control of the Fano factor. Copyright EDP Sciences, SIF, Springer-Verlag Berlin Heidelberg 2010

AC shot noise through a vibrating quantum dot

In this paper we investigate the joint effects of the electron-phonon interaction and an external alternating (ac) gate voltage on the spectral density of shot noise through a vibrating quantum dot system, by applying the Lang-Firsov canonical transformation and the Keldysh nonequilibrium Green's function (NGF) technique. We find that the effects of the electron-phonon and electron-photon interaction on the differential shot noise are different. The main resonant peak of the differential shot noise is decreased only when a time-dependent gate voltage is imposed on quantum dot. With the ac field amplitude increasing, the main resonant peak of the differential shot noise decreases. The Fano factor of the system, which exhibits the deviation of shot noise from the Schottky formula, is also studied. Super-Poissonian shot noise appears due to the photon absorption (emission) processes in the low bias voltage region

Photon-assisted shot noise due to the charging effect in a quantum dot device

85.35.-p Nanoelectronic devices, 73.23.-b Electronic transport in mesoscopic systems, 72.10.Bg General formulation of transport theory, 73.21.La Quantum dots,