Two-phonon contributions to inelastic x-ray scattering spectra of MgB2

TL;DR

This paper identifies two-phonon contributions in inelastic x-ray scattering spectra of MgB2 at 300K, showing good agreement with harmonic calculations and highlighting their impact on phonon linewidths related to high-temperature superconductivity.

Contribution

It presents the first observation of peaks due to 2-phonon scattering in non-rare-gas solids, advancing understanding of phonon interactions in MgB2.

Findings

Two-phonon contributions match harmonic calculations

Impact on linewidth determination of E2g phonon mode

First observation of 2-phonon peaks in non-rare-gas solids

Abstract

Two-phonon contributions to meV-resolved inelastic x-ray scattering spectra of MgB2 at 300K are identified, in good agreement, in both intensity and energy, with a harmonic calculation using the force constant matrix from ab-inito LDA calculations. This contribution impacts the determination of the linewidth of the E2g phonon mode that is so important for the high Tc of this material. To the best of our knowledge, this is the first observation of peaks in measurements of phonon dispersion (q>0) due to 2-phonon scattering in a non-rare-gas solid.