Vibronic states in the conductance of single C60 and C70 molecules by STM

COLL 401

Ning Liu1, Nilay A. Pradhan1, and Wilson Ho2. (1) Department of Physics and Astronomy, University of California, Irvine, University of California, Irvine, 4129 Frederick Reines Hall, Irvine, CA 92697-4575, (2) Department of Physics and Chemistry, University of California, Irvine, Irvine, CA 92697
Vibronic states are observed in single C60 and C70 molecules by a scanning tunneling microscope. When single C60 and C70 molecules are adsorbed on a thin layer of Al2O3 grown on NiAl(110) substrate, fine featuers are displayed in the dI/dV spectra, which appear as a series of equally spaced peaks in d2I/dV2 spectra. Vibronic progressions with different spacings can be observed in the same molecule. These vibronic peaks correspond to the intramolecular Hg vibrational modes, which are believed to contribute to the electron pairing mechanism in superconductivity. Vibronic states are not resolved in molecules adsorbed on the bare NiAl(110) surface.