Neutron Scattering and the B_{1g} Phonon in the Cuprates

TL;DR

This paper models the momentum-dependent lineshape of a specific phonon mode in cuprate superconductors using neutron scattering data, highlighting the importance of anisotropic electronic properties and electron-phonon interactions.

Contribution

It introduces a microscopic model linking phonon lineshape changes to local crystal field coupling and anisotropic electronic features in cuprates.

Findings

Phonon lineshift and broadening depend on transferred momentum.

Anisotropy in density of states and gap influences phonon behavior.

Electron-phonon coupling is crucial for explaining experimental results.

Abstract

The momentum dependent lineshape of the out-of-phase oxygen vibration as measured in recent neutron scattering measurements is investigated. Starting from a microscopic coupling of the phonon vibration to a local crystal field, the phonon lineshift and broadening is calculated as a function of transfered momentum in the superconducting state of YBa$_{2}$Cu$_{3}$O$_{7}$. It is shown that the anisotropy of the density of states, superconducting energy gap, and the electron-phonon coupling are all crucial in order to explain these experiments.