Existence Of Metallic Phase Research Articles

ELECTRICAL TRANSPORT PROPERTIES OF C60 SINGLE CRYSTALS DOPED WITH ALKALI METALS

Electronic structures of various kinds of alkali metal (Na, K, Rb or Cs)-doped C 60 solids are studied by electrical resistivity and thermoelectric power measurements by using C 60 single crystals prepared from a CS 2 solution as a starting material. For K-or Rb-doped C 60, metallic conducting behaviors in the normal conducting state and relatively sharp superconducting transitions are observed by the electrical resistivity measurements. Nearly linear-temperature dependences with the negative sign are observed in the thermoelectric power measurements at the normal conducting states for K-or Rb-doped C 60. From electron diffusion term of the thermoelectric power, the values of Fermi energy and the density of states at the Fermi energy are estimated by assuming the three-dimensional free electron model, which are in substantial agreement with the results of other experiments and calculations. "Metal–semiconductor transition" is observed in both the electrical resistivity and the thermoelectric power measurements for Na-doped C 60. Existence of metallic phase is confirmed by the thermoelectric power measurement in Cs-doped C 60.