Charge density waves in Sr_14-xCa_xCu_24O_41: electron correlations vs. structural effects

TL;DR

This study uses inelastic light scattering to investigate charge density wave formation in Sr_14-xCa_xCu_24O_41, revealing the influence of structural effects and electron correlations on charge dynamics in ladders and chains.

Contribution

It provides new insights into how structural incommensurability and Ca substitution affect charge density waves in the spin-chain and ladder system.

Findings

Depletion of electronic background indicates 2D charge density wave formation.

Charge dynamics are strongly influenced by structural incommensurability.

Ca substitution affects lattice modulations and charge modes.

Abstract

We report inelastic light scattering experiments in the spin-chain and ladder system Sr_14-xCa_xCu_24O_41. A depletion of an electronic background is observed for 0 < x < 5 at low temperatures and with light polarization both parallel to the leg and rung directions. This points to the formation of 2D charge density wave in the ladders. Furthermore, the Ca-substitution dependence of the 305- and 249-cm-1 modes, sensitive to the lattice modulations of the respective chain and ladder system, suggests that the charge dynamics in the ladders is strongly influenced by the structural incommensurability.