Metallic behaviour of carrier-polarized C${}_{60}$ molecular layers: Experiment and Theory

Abstract

Although C${}_{60}$ is a molecular crystal with a bandgap E${}_g$ of ~2.5 eV, we show that E${}_g$ is strongly affected by injected charge. In sharp contrast to the Coulomb blockade typical of quantum dots, E${}_g$ is {\it reduced} by the Coulomb effects. The conductance of a thin C${}_{60}$ layer sandwiched between metal (Al, Ag, Au, Mg and Pt) contacts is investigated. Excellent Ohmic conductance is observed for Al electrodes protected with ultra-thin LiF layers. First-principles calculations, Hubbard models etc., show that the energy gap of C${}_{60}$ is dramatically reduced when electrons hop from C${}_{60}^{-}$ to C${}_{60}$.

4 PRL style pages, 2 figures. email: [email protected]