Switchable zero-bias anomaly in individual C₆₀ molecules contacted with tunable aluminum electrodes

摘要

We report the observation of strong resonances at zero bias in the differential conductance through Al–C₆₀–Aludjunctions with tunable electrode distance, measured above T = 10 K. The conductance value at resonance rangesudfrom a few percent up to eighty percent of the quantum of conductance. The resonances may disappear or reoccurudcompletely and discontinuously upon very small changes of the electrode distance. However, once they areudformed they are very robust with respect to changes of the electrode distance. We discuss similarities and differencesudto the common theories of the Kondo screening of a spontaneous spin polarization of the C₆₀ molecule.udWe deduce Kondo temperatures in the range from 35 to 160 K and demonstrate that the temperature dependenceudis in agreement with the scaling behavior of the Kondo effect in the temperature range of our experiment.