Applied-field effects on molecular switches

Electron transmission through an electrified composite metal-doped polymer-metal system is investigated by means of the Lippmann-Schwinger equation. The electric field, applied via the metal leads, acts across the polymer chain containing the single-impurity atom, which behaves as a molecular switch. The Stark-ladder effect in the doped polymer is described by utilizing the recursive-Green-function (RGF) approach, where repeated use of the Dyson equation gives rise to a continued-fraction form of the RGF, which can be expressed analytically as a ratio of Bessel functions. Molecular switch control of the transmission is achieved by adjusting the parameters characterizing the impurity. The influence of the applied field on the transmission process is discussed.