Resonant tunneling through discrete electronic levels of a C₆₀ molecule in the presence of charging effects

We have conducted tunneling spectroscopy studies for isolated C₆₀ molecules in the double barrier tunnel junction configuration. The tunneling current-voltage (I - V) and dI/dV vs. V spectra of these molecules exhibit rich structures resulting from both resonant tunneling through the discrete levels and single electron charging effects. In particular, we observe degeneracy lifting within the molecular orbitals, probably due to the Jahn-Teller effect and local electric fields. Theoretical fits, performed using the "orthodox" model for single-electron tunneling modified to account for the discrete level spectrum of C₆₀, agree well with our data.