Volume 102, Number 1, April 2013
|Number of page(s)||6|
|Section||Condensed Matter: Electronic Structure, Electrical, Magnetic and Optical Properties|
|Published online||08 April 2013|
Challenging the nature of low-energy plasmon excitations in CaC6 using electron energy-loss spectroscopy
1 IFW Dresden - P.O. Box 270116, D-01171 Dresden, Germany, EU
2 University of Vienna, Faculty of Physics - Strudlhofgasse 4, AT-1090, Vienna, Austria, EU
Received: 25 February 2013
Accepted: 19 March 2013
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 CaC. 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 CaC 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 CaC. However its optical limit at 1 eV challenges the theoretical predictions and safely rules out an electronic superconducting coupling mechanism in CaC
PACS: 79.20.Uv – Electron energy loss spectroscopy / Electron energy loss spectroscopy – / 71.20.Tx – / Fullerenes and related materials; intercalation compounds – / 81.05.uf – / Graphite –
© EPLA, 2013
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