Electron-phonon coupling in the conventional superconductor YNi$_2$B$_2$C at high phonon energies studied by time-of-flight neutron spectroscopy

TL;DR

This study uses advanced neutron scattering techniques to measure high-energy phonons in YNi₂B₂C, revealing detailed phonon dispersion and linewidths that align well with ab-initio calculations, enhancing understanding of electron-phonon interactions.

Contribution

First comprehensive experimental measurement of high-energy phonons in YNi₂B₂C using time-of-flight neutron spectroscopy, validating ab-initio calculations across the entire phonon spectrum.

Findings

High-energy phonons up to 159 meV characterized in YNi₂B₂C.

Experimental linewidths agree with theoretical predictions.

A₁g phonons have limited contribution to electron-phonon coupling.

Abstract

We report an inelastic neutron scattering investigation of phonons with energies up to 159 meV in the conventional superconductor YNi$_2$B$_2$C. Using the SWEEP mode, a newly developed time-of-flight technique involving the continuous rotation of a single crystal specimen, allowed us to measure a four dimensional volume in (Q,E) space and, thus, determine the dispersion surface and linewidths of the $A_{1g}$ (~ 102 meV) and $A_u$ (~ 159 meV) type phonon modes for the whole Brillouin zone. Despite of having linewidths of $\Gamma = 10 meV$, $A_{1g}$ modes do not strongly contribute to the total electron-phonon coupling constant $\lambda$. However, experimental linewidths show a remarkable agreement with ab-initio calculations over the complete phonon energy range demonstrating the accuracy of such calculations in a rare comparison to a comprehensive experimental data set.