We report measurements of phonon dispersion in CaC6 using inelastic x-ray and neutron scattering. We find good overall agreement, particularly in the 50 meV energy region, between experimental data and first-principles density-functional-theory calculations. However, on the longitudinal dispersion along the (111) axis of the rhombohedral representation, we find an unexpected anticrossing with an additional longitudinal mode, at about 11 meV. At a comparable energy, we observe also unexpected intensity on the in-plane direction. These results resolve the previous incorrect assignment of a longitudinal phonon mode to a transverse mode in the same energy range. By calculating the electron susceptibility from first principles we show that this longitudinal excitation is unlikely to be due to a plasmon and consequently can probably be due to defects or vacancies present in the sample. © 2010 The American Physical Society.

Phonon dispersion and low-energy anomaly in CaC6 from inelastic neutron and x-ray scattering experiments / D'Astuto, M.; Calandra, M.; Bendiab, N.; Loupias, G.; Mauri, F.; Zhou, S.; Graf, J.; Lanzara, A.; Emery, N.; Herold, C.; Lagrange, P.; Petitgrand, D.; Hoesch, M.. - In: PHYSICAL REVIEW. B, CONDENSED MATTER AND MATERIALS PHYSICS. - ISSN 1098-0121. - 81:10(2010). [10.1103/PhysRevB.81.104519]

Phonon dispersion and low-energy anomaly in CaC6 from inelastic neutron and x-ray scattering experiments

Calandra M.;
2010-01-01

Abstract

We report measurements of phonon dispersion in CaC6 using inelastic x-ray and neutron scattering. We find good overall agreement, particularly in the 50 meV energy region, between experimental data and first-principles density-functional-theory calculations. However, on the longitudinal dispersion along the (111) axis of the rhombohedral representation, we find an unexpected anticrossing with an additional longitudinal mode, at about 11 meV. At a comparable energy, we observe also unexpected intensity on the in-plane direction. These results resolve the previous incorrect assignment of a longitudinal phonon mode to a transverse mode in the same energy range. By calculating the electron susceptibility from first principles we show that this longitudinal excitation is unlikely to be due to a plasmon and consequently can probably be due to defects or vacancies present in the sample. © 2010 The American Physical Society.
2010
10
D'Astuto, M.; Calandra, M.; Bendiab, N.; Loupias, G.; Mauri, F.; Zhou, S.; Graf, J.; Lanzara, A.; Emery, N.; Herold, C.; Lagrange, P.; Petitgrand, D.; Hoesch, M.
Phonon dispersion and low-energy anomaly in CaC6 from inelastic neutron and x-ray scattering experiments / D'Astuto, M.; Calandra, M.; Bendiab, N.; Loupias, G.; Mauri, F.; Zhou, S.; Graf, J.; Lanzara, A.; Emery, N.; Herold, C.; Lagrange, P.; Petitgrand, D.; Hoesch, M.. - In: PHYSICAL REVIEW. B, CONDENSED MATTER AND MATERIALS PHYSICS. - ISSN 1098-0121. - 81:10(2010). [10.1103/PhysRevB.81.104519]
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11572/261784
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