TRANSPORT-PROPERTIES OF OXYGEN-DEFICIENT YBA2CU3O7-X THIN-FILMS

We report on measurements of the in-plane resistivity rho and Hall coefficient R(H)(B \\ c) of various oxygen-deficient epitaxial films of YBa2Cu3O7-x in the normal state. The superconducting transition temperatures T(c) of the samples vary from 14 to 90 K. Both the resistivity and the Hall coefficient exhibit a strong dependence on the oxygen content and the temperature. As x increases, T(c) decreases continuously, while rho and R(H) gradually increase in magnitude. Furthermore, also the characteristic linear dependences of rho proportional-to T and R(H) is-proportional-to T-1 of the highly doped compounds changes to a nonlinear behavior for the samples with T(c) lower than 60 K. The unusual doping and temperature dependence of R(H) will be compared to the predictions of our calculations, based on a two-dimensional tight-binding model using the relaxation-time approximation. The model considers also the next-nearest-neighbor hopping, which strongly influences the predicted Hall coefficient. Additionally, the cotangent of the Hall angle cot(THETA(H)) is discussed in the framework of the two-dimensional Luttinger liquid theory.