The smallest molecular switch.

Ab initio total energy calculations reveal benzene-dithiolate molecules on a gold surface, contacted by a monatomic gold STM tip to have two classes of low-energy conformations with differing symmetries. Lateral motion of the tip or excitation of the molecule cause it to change from one conformation class to the other and to switch between a strongly and a weakly conducting state. Thus, surprisingly, despite their apparent simplicity, these Au/BDT/Au nanowires are shown to be electrically bistable switches, the smallest two-terminal molecular switches to date.