C-axis Transport in Bilayer Cuprates and Relation to Pseudogap

TL;DR

This paper investigates how interband transitions influence c-axis transport properties in bilayer cuprates, revealing how the pseudogap and interlayer coupling affect conductivity and resistivity behaviors.

Contribution

It provides a theoretical analysis of c-axis transport considering interband effects and relates these to the pseudogap phenomenon in bilayer cuprates.

Findings

Small interlayer hopping causes resistivity upturns and pseudogap features.

Increasing interlayer hopping leads to more conventional conductivity responses.

Analytical results include the optical conductivity sum rule for bilayer systems.

Abstract

We consider the effect of interband transitions on the c-axis conductivity, DC resistivity, and thermal conductivity in a plane-chain bilayer model of a cuprate. The relation between the c-axis resistivity and thermal conductivity is governed by the Wiedemann-Franz law. When the perpendicular hopping matrix element between chain and plane ($t_\perp$) is small, the c-axis DC resistivity shows a characteristic upturn as the temperature is lowered and the infrared conductivity develops a pseudogap. As $t_\perp$ is increased, intraband transitions start to dominate and a more conventional response is obtained. Analytical results for a simple plane-plane bilayer are also given, including the frequency sum rule of the optical conductivity.