Suppressing the current through molecular wires: Comparison of two mechanisms

Abstract

The electron tunneling through a molecular junction weakly coupled to two leads is studied in the presence of a time-dependent external field. For this purpose, the wire is modeled in a tight-binding approach and a master equation approach is employed. Two different ways of suppressing the current through the wire are compared: coherent destruction of tunneling (CDT) and a laser field obtained by optimal control theory. The CDT localizes the electrons at the individual sites and it is effective if the amplitude of a high-frequency laser field fulfills a certain amplitude criterion. As the name of the phenomenon indicates, it is a coherent effect. In the alternative approach, the optimal control theory, a target current flow pattern is defined and the corresponding laser field is calculated. It is shown that the two mechanisms are influenced differently by introducing dephasing effects into the system. Furthermore, the currents flowing in, through and out of the wire are investigated in more detail to understand the physical processes behind the suppression of the net current. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.