Challenging the nature of low-energy plasmon excitations in CaC6 using electron energy-loss spectroscopy

Autor(en)

Friedrich Roth, Andreas König, Christian Kramberger, Thomas Pichler, Bernd Büchner, Martin Knupfer

Abstrakt

The nature of low-energy plasmon excitations plays an important role in understanding the low-energy electronic properties and coupling mechanism of different superconducting compounds such as CaC6. Recent ab initio studies predict a charge carrier intraband plasmon in keeping with a low-energy acoustic plasmon. Here, we have studied the low-energy electronic excitations of CaC6 using high-resolution electron energy-loss spectroscopy in transmission at low temperatures. The analysis of the core level excitations leads to the conclusion that hybridization between graphite and calcium states plays an essential role in this graphite-intercalated compound. Regarding the low-energy plasmon excitation, we observe the formation of an intraband (charge carrier) plasmon with a negative dispersion at about 3.5 eV in sound agreement with the theory. Finally, a weak excitation around 1.2 eV with an almost linear dispersion relation can be observed as predicted for an acoustic plasmon that may mediate the superconducting coupling in CaC6. However its optical limit at ~1 eV challenges the theoretical predictions and safely rules out an electronic superconducting coupling mechanism in CaC6.

Organisation(en)

Elektronische Materialeigenschaften

Externe Organisation(en)

Leibniz-Institut für Festkörper- und Werkstoffforschung Dresden

Journal

Europhysics Letters

Band

102

Anzahl der Seiten

6

ISSN

0295-5075

DOI

https://doi.org/10.1209/0295-5075/102/17001

Publikationsdatum

04-2013

Peer-reviewed

Ja

ÖFOS 2012

103020 Oberflächenphysik, 103009 Festkörperphysik, 103018 Materialphysik

Schlagwörter

Link zum Portal

https://ucrisportal.univie.ac.at/de/publications/08a6c781-884f-4e13-8a82-e9f6f193cdc6