Bulk charge density wave and electron-phonon coupling in superconducting copper oxychlorides

TL;DR

This study reveals bulk charge density waves in copper oxychloride superconductors using resonant inelastic X-ray scattering, highlighting electron-phonon interactions and phonon anomalies linked to charge excitations.

Contribution

It demonstrates the presence of bulk charge density waves in copper oxychlorides and explores their interaction with lattice vibrations using advanced X-ray scattering techniques.

Findings

Charge density waves are present in copper oxychlorides.

Electron-phonon coupling shows anomalies at the CDW wave-vector.

Dispersive charge excitations interact with Cu-O bond-stretching phonons.

Abstract

Bulk charge density waves are now reported in nearly all high-temperature superconducting cuprates, with the noticeable exception of one particular family: the copper oxychlorides. Here, we used resonant inelastic X-ray scattering to reveal a bulk charge density waves in these materials. Combining resonant inelastic X-ray scattering with non-resonant inelastic X-ray scattering, we investigate the interplay between the lattice excitations and the charge density wave, and evidence the phonon anomalies of the Cu-O bond-stretching mode at the charge density wave wave-vector. We propose that such electron-phonon anomalies occur in the presence of dispersive charge excitations emanating from the charge density wave and interacting with the Cu-O bond-stretching phonon. Our results pave the way for future studies, combining both bulk and surface probes, to investigate the static and dynamical properties of the charge density wave in the copper oxychloride family.