Detection of Acoustic Plasmons in Hole-Doped Lanthanum and Bismuth Cuprate Superconductors Using Resonant Inelastic X-Ray Scattering

TL;DR

This study uses resonant inelastic X-ray scattering to detect acoustic plasmons in hole-doped cuprate superconductors, revealing their association with oxygen sites and completing the understanding of charge excitations in these materials.

Contribution

First observation of acoustic plasmons in hole-doped cuprates using RIXS, highlighting their link to oxygen sites and expanding knowledge of charge dynamics.

Findings

Acoustic plasmons observed in hole-doped cuprates LSCO and Bi2201.

Acoustic plasmons predominantly associated with oxygen sites.

Completes the understanding of charge excitations in hole-doped cuprates.

Abstract

High Tc superconductors show a rich variety of phases associated with their charge degrees of freedom. Valence charges can give rise to charge ordering or acoustic plasmons in these layered cuprate superconductors. While charge ordering has been observed for both hole- and electron-doped cuprates, acoustic plasmons have only been found in electron-doped materials. Here, we use resonant inelastic X-ray scattering (RIXS) to observe the presence of acoustic plasmons in two families of hole-doped cuprate superconductors [La2-xSrxCuO4 (LSCO) and Bi2Sr1.6La0.4CuO6+d (Bi2201)], crucially completing the picture. Interestingly, in contrast to the quasi-static charge ordering which manifests at both Cu and O sites, the observed acoustic plasmons are predominantly associated with the O sites, revealing a unique dichotomy in the behaviour of valence charges in hole-doped cuprates.