Electrical transport property of polymerized KC60 and RbC60 Original Research Article

We have measured the temperature-dependent ac and dc resistivities of polymerized crystalline KC60 and RbC60 between room temperature and 4.2 K at atmospheric pressure, as well as the resistivity of polymerized RbC60 under 5 kbar. The first-order phase transition occurs around 100 K for RbC60 at clamping pressure of 5 kbar. The ac resistivity behaves as dc resistivity for KC60, both reveal a metal-like character at room temperature and a metal–semiconductor phase transition near 50 K. But the ac resistivity of RbC60 reveals a remarkably different feature from that of dc measurement, and shows a semiconducting behavior at atmospheric pressure and a frequency dependent resistivity peak at low temperature. The effects of the inherent capacitance resulting from the weakly coupled boundaries in a sample are studied. Possible mechanisms for these observations are discussed.