Suppression of the charge-density-wave state in Sr_14Cu_24O_41 by calcium doping

TL;DR

This study investigates how calcium doping suppresses the charge-density-wave state in Sr_14Cu_24O_41, revealing the mechanisms behind the phase transition and implications for potential superconductivity.

Contribution

It provides detailed experimental evidence on how calcium doping affects the CDW phase and its transition temperature in Sr_14Cu_24O_41, highlighting the role of electronic structure changes.

Findings

Calcium doping reduces the CDW transition temperature from 210 K to 10 K.

The CDW gap decreases from 130 meV to 3 meV with doping.

Suppression of CDW suggests potential for two-dimensional superconductivity under pressure.

Abstract

The charge response in the spin chain/ladder compound Sr_14-xCa_xCu_24O_41 is characterized by DC resistivity, low-frequency dielectric spectroscopy and optical spectroscopy. We identify a phase transition below which a charge-density wave (CDW) develops in the ladder arrays. Calcium doping suppresses this phase with the transition temperature decreasing from 210 K for x=0 to 10 K for x=9, and the CDW gap from 130 meV down to 3 meV, respectively. This suppression is due to the worsened nesting originating from the increase of the inter-ladder tight-binding hopping integrals, as well as from disorder introduced at the Sr sites. These results altogether speak in favor of two-dimensional superconductivity under pressure.