Abrupt Change in Dark Conductivity on C60 Polycrystalline Films at the Rotational Order/Disorder Transition

概要

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The temperature dependence of dark conductivity of C60 fullerites in the form of polycrystalline films sandwiched between metal electrodes is systematically studied. At the rotational order/disorder phase transition temperature $T_{\text{c}}$ of about 256 K, an abrupt change in dark conductivity of 4–5 orders of magnitude within a narrow temperature range of less than 2 K is observed. The conductivity for this sample decreases as the temperature crosses $T_{\text{c}}$ from fcc phase to sc phase. From the Arrhenius plot of dark conductivity, the activation energies are estimated to be $53\pm 4$ meV for the fcc phase and $111\pm 6$ meV for the sc phase. To explain these experimental findings, the electric transport through parallel, extremely pure, and homogeneous C60 monocrystals between two metal contacts is postulated and described, and a model based on the local lattice potential induced by rotational order of C60 molecules is proposed.
INSTITUTE OF PURE AND APPLIED PHYSICSの論文
2002-10-15