Laser field alignment of organic molecules on semiconductor surfaces: toward ultrafast molecular switches.

An ultrafast, nanoscale molecular switch is proposed, based on extension of the concept of nonadiabatic alignment to surface-adsorbed molecules. The switch consists of a conjugated organic molecule adsorbed onto a semiconducting surface and placed near a scanning tunneling microscope tip. A low-frequency, polarized laser field is used to switch the system by orienting the molecule with the field polarization axis, enabling conductance through the junction. Enhancement and spatial localization of the incident field by the metallic tip allow operation at low intensities. The principles of nonadiabatic alignment lead to switch on and off time scales far below rotational time scales.