Highly anisotropic anomaly in the dispersion of the copper-oxygen bond-bending phonon in superconducting YBa2Cu3O7 from inelastic neutron scattering

TL;DR

This study uses inelastic neutron scattering to investigate the anisotropic behavior of a specific phonon in YBa2Cu3O7, revealing an anomaly that suggests electron-phonon interactions linked to charge-density modulations rather than d-wave superconductivity.

Contribution

It provides new experimental evidence on phonon anisotropy and its implications for electron-phonon interactions in cuprate superconductors.

Findings

Pronounced phonon softening at q = (0, 0.3) below 105 K

No anomaly observed at q = (0.3, 0)

Anisotropic electron-phonon interaction linked to charge-density modulation

Abstract

Motivated by predictions of a substantial contribution of the "buckling" vibration of the CuO2 layers to d-wave superconductivity in the cuprates, we have performed an inelastic neutron scattering study of this phonon in an array of untwinned crystals of YBa2Cu3O7. The data reveal a pronounced softening of the phonon at the in-plane wave vector q = (0, 0.3) upon cooling below ~ 105 K, but no corresponding anomaly at q = (0.3, 0). Based on the observed in-plane anisotropy, we argue that the electron-phonon interaction responsible for this anomaly supports an electronic instability associated with a uniaxial charge-density modulation and does not mediate d-wave superconductivity.