Current-induced rotations of molecular gears

International audienceDownsizing of devices opens the question of how to tune not only their electronic properties, but alsoof how to influence ‘mechanical’ degrees of freedom such as translational and rotational motions.Experimentally, this has been meanwhile demonstrated by manipulating individual molecules withe.g. current pulses from a Scanning Tunneling Microscope tip. Here, we propose a rotational versionof the well-known Anderson-Holstein model to address the coupling between collective rotationalvariables and the molecular electronic system with the goal of exploring conditions for unidirectionalrotation. Our approach is based on a quantum–classical description leading to effective Langevinequations for the mechanical degrees of freedom of the molecular rotor. By introducing a timedependentgate to mimic the influence of current pulses on the molecule, we show that unidirectionalrotations can be achieved by fine tuning the time-dependence of the gate as well as by changing therelative position of the potential energy surfaces involved in the rotational proces