Manipulating electric current at the nanoscale is an important challenge: logic gates, computation and sensing are among areas of potential application. NU-MRSEC researchers proposed a nanoscale, ultrafast molecular switch controlled by the coherence properties of an optical pulse. Their work overcomes the hurdle that prevented realization of previous proposals. The switch consists of an organic molecule adsorbed onto a semiconducting surface and placed near a scanning tunneling microscope tip. A low-frequency, polarized laser field serves to swiftly orient the molecule through an effect known as non-adiabatic alignment, thus switching the current on. Plasmonic enhancement and spatial localization of the laser field by the tip allows operation at low intensity. The principles of nonadiabatic alignment lead to sub-ps switch-on and -off time scales. The calculation illustrates an on-off ratio above 2 orders of magnitude and an on-off time of 0.6 ps.
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