Unusual metallic in-plane and non-metallic c-axis charge transports in underdoped cuprates

Abstract

We develop the theory of the metallic in-plane and non-metallic c-axis conductivities in the underdoped cuprates within the large (bi) polaron model and the precursor pairing model by considering a two-component charge carrier picture and the carrier-acoustic phonon scattering. The metallic transports of large polarons above the pairing pseudogap temperature T ∗ and polaron Cooper pairs below T ∗ in the CuO 2 layers of the cuprates are studied by using the appropriate Boltzmann equations in the relaxation time approximation and the extended BCS-like pairing model. We show that the in-plane resistivity in underdoped cuprates follows a T-linear law above T ∗ and deviates from the T-linear behavior below T ∗due to the precursor BCS-like pairing of large polarons. We argue that the non-metallic c-axis transport in these systems is caused by the dissociation of localized large bipolarons into two polarons and the motion of nondegenerate polarons scattered at acoustic phonons. The resistivity anisotropy is determined and compared with experimental results.