The role of intermediate layers in the C axis conductivity of layered superconductors

A simplified model of c axis transport in the high T-c superconductors is p resented. Expressions are found for the c axis optical conductivity, the d. c. resistivity, and the c axis penetration depth. Within the framework of t his model, the pseudogap in the optical conductivity arises naturally as a result of the layered band structure of the high T-c materials. We discuss the occurrence of the pseudogap in terms of three parameters: a bandgap Del ta(ps), a temperature dependent scattering rate Gamma(T), and the strength of the interlayer coupling t(perpendicular to). We are also able to find an alytic expressions for the d.c. conductivity and the low temperature penetr ation depth in terms of these three parameters. This work is an attempt to present a simple, unified picture of c axis properties in the high T-c cupr ates. (C) 1998 Elsevier Science Ltd. All rights reserved.