AC and DC Conductivity Anisotropies in Lightly Doped La(2-x)Sr(x)CuO(4)

TL;DR

This study investigates the anisotropic AC and DC conductivities in lightly doped La(2-x)Sr(x)CuO(4), attributing the effects to impurity states caused by doped holes trapped by Sr ions, revealing distinct absorption energies and directional hopping channels.

Contribution

It provides a detailed explanation of conductivity anisotropies based on impurity states and orthorhombic symmetry breaking, with quantitative analysis of the observed phenomena.

Findings

Two distinct infrared absorption energies due to impurity states.

Quantitative match between hopping channels and conductivity anisotropies.

Identification of impurity-induced localized states affecting transport.

Abstract

The AC and DC conductivity anisotropies in the low temperature orthorhombic phase of lightly doped La(2-x)Sr(x)CuO(4) are ascribed to the rotational symmetry broken, localized impurity states resulting from the trapping of doped holes by Sr ions. The two lowest-energy p-wave-like states are split by orthorhombicity and partially filled with holes. This leaves a unique imprint in AC conductivity, which shows two distinct infrared continuum absorption energies. Furthermore, the existence of two independent channels for hopping conductivity, associated to the two orthorhombic directions, explains quantitatively the observed low temperature anisotropies in DC conductivity.