Physics – Condensed Matter – Materials Science
Scientific paper
2007-03-05
Physical Review B vol. 75 (2007)
Physics
Condensed Matter
Materials Science
11 pages, 10 figures
Scientific paper
10.1103/PhysRevB.75.174508
We study anharmonic effects in MgB2 by comparing Inelastic X-ray and Ramanscattering together with ab-initio calculations. Using high statistics and high q resolution measurements we show that the E2g mode linewidth is independent of temperature along Gamma-A. We show, contrary to previous claims, that the Raman-peak energy decreases as a function of increasing temperature, a behaviour inconsistent with all the anharmonic ab-initio calculations of the E2g mode at Gamma available in literature. These findings and the excellent agreement between the X-ray measured and ab-initio calculated phonon spectra suggest that anharmonicity is not the main mechanism determining the temperature behaviour of the Raman-peak energy. The Raman E2g peak position and linewidth can be explained by large dynamical effects in the phonon self-energy. In light of the present findings, the commonly accepted explanation of the reduced isotope effect in terms of anharmonic effects needs to be reconsidered.
Bossak Alexei A.
Calandra Matteo
d'Astuto Matteo
Karpinski Janusz
Krisch Michael
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