Bi-Stable States in Highly Conductive Pyrazine Molacular Junction

Bi-stable molecular junctions are recently deserving attention for their potential in molecular electronics applications. In the present work, we investigate the bi-stable conductance of highly conductive single-molecule pyrazine/Pt junctions. Break-junction measurements show two distinct conductance states of 1.0 G$_{\mathrm{0}}$ and 0.3 G$_{\mathrm{0}}$, G$_{\mathrm{0}}$ being the quantum of conductance. First-principles calculations reveal that the two states could be assigned to different geometrical configurations of pyrazine exhibiting larger and lower coupling with the electrodes, respectively. Inelastic tunneling electron spectroscopy measurements and theoretical analysis of the system vibrations are able to further characterize the configuration dependent conductance of such junctions. We demonstrate that the controlled torsion of the molecule is capable to switch between the two conducting regimes. This process triggered only by mechanical manipulation of the junction is reversible.