Conductivity And Paraconductivity In (Bi,Pb)2sr2can-1cunox Whiskers

We have measured the resiStiVitY Of (Bi,Pb)2Sr2Can-1CunOx single-crystal whiskers in the a and c directions. Our results indicate that the whiskers may be either 2:2:1:2 (n = 1) or 2:2:2:3 (n = 2) or have both phases present. Well above T(c), the resistivity in the a direction decreases linearly with temperature. We also studied the paraconductivity due to thermal fluctuations above T(c). The paraconductivity in the a direction shows quasi-one-dimensional behavior for temperatures close to T(c). This quasi-one-dimensional behavior may be due to a percolative conduction path. For the c direction, the resistivity is best fit by rho(c) = Ae(-Eg/kT), where T is the temperature. However, as T approaches T(c) from above, rho(c) increases much faster than a thermally activated law, perhaps because of the fluctuations.