In-Plane and Out-of-Plane Charge Dynamics of High-$T_c$ Cuprates

TL;DR

This paper develops a theoretical model for the dielectric response of layered high-temperature cuprates, linking plasma frequencies to experimental optical data and exploring anisotropic charge dynamics and coherence issues.

Contribution

It introduces a new theoretical expression for the dielectric function of layered cuprates, connecting plasma frequencies to optical measurements and analyzing anisotropic charge transport effects.

Findings

Plasma frequencies at zero wavevector match experimental optical data.

Strong anisotropy affects charge transport and coherence across layers.

The model accounts for the layered structure and strong correlations in cuprates.

Abstract

We propose a theoretical expression for the $k$- and $\omega$-dependent dielectric function of a stack of two-dimensional layers coupled along the direction perpendicular to the layers, and discuss some of its properties. We argue that the plasma frequencies at $k=0$ should correspond to those which are experimentally obtained from optical measurements on {\em e.g.} La$_{1-x}$Sr$_{x}$CuO$_4$ via the $f$-sum rule analysis, regardless of the fact that such systems are strongly correlated. We discuss some of the ramifications due to strong anisotropy of the charge transport in these systems, and the lack of coherence for the transport in the direction perpendicular to the layers.