Normal state transport properties of single- and double-layered Bi 2Sr 2Ca n−1Cu nO y thin films and the pseudogap effect

Abstract

The temperature dependence of the in-plane resistivity ρ(T) of epitaxial c-axis oriented single-layered Bi 2Sr 1.6La 0.4CuO y and double-layered Bi 2Sr 2CaCu 2O y thin films was investigated for various oxygen contents. Each film of either phase was transformed, by successive annealing treatments, from a maximally overdoped state through its optimally doped state (T cmax=30 K and 80 K respectively) to a strongly underdoped non-superconducting state. For overdoped states, ρ(T) can be described by a phenomenological law of the form: a+bT m with 1≤m≤1.3. For both phases, in the underdoped region, we observe a downward deviation of the resistivity from the high-T linear behavior, attributed to pseudogap opening. The temperature T* where this downturn occurs increases sharply with decreasing doping. This dependence is displayed in the universal phase diagram (temperature vs doping) which is established for each phase. We also show that a unique curve can describe the effect of the pseudogap on the variation of resistivity with temperature for each phase. A comparison with the available theoretical descriptions of ρ(T) is made. The similarities and differences observed between single- and double-layered compound behavior are discussed.