Kohn Anomaly in MgB2 by Inelastic X-Ray Scattering
A. Q. R. Baron (1), H. Uchiyama (2), Y. Tanaka (3), S. Tsutsui (1), D., Ishikawa (3), S. Lee (2), R. Heid (4), K.-P. Bohnen (4), S. Tajima (2), T., Ishikawa (1, 3) ((1) SPring-8/JASRI, (2) Superconductivity Research, Laboratory, ISTEC, (3) SPring-8/RIKEN
TL;DR
This study uses inelastic x-ray scattering to investigate phonon behavior in MgB2, confirming theoretical predictions of phonon dispersion and linewidth, and revealing a previously unpredicted longitudinal mode near the E2g mode.
Contribution
It provides experimental validation of phonon dispersion and linewidth in MgB2, and reports a new longitudinal mode not predicted by existing theory.
Findings
Excellent agreement with theoretical phonon dispersion and linewidth.
Observation of softening and broadening of the E2g mode at the Kohn anomaly.
Detection of a longitudinal mode near the E2g mode not predicted by theory.
Abstract
We study phonons in MgB2 using inelastic x-ray scattering (1.6 and 6 meV resolution). Our measurements show excellent agreement with theory for the dispersion and line-width: we clearly observe the softening and broadening of the crucial E2g mode through the Kohn anomaly along GM. Low temperature measurements (just above and below Tc) show negligible changes for the momentum-transfers investigated, and no change in the E2g mode at A between room temperature and 16K. We report the presence of a longitudinal mode along GA near in energy to the E2g mode that is not predicted by theory.
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