Raman study of the two-dimensional polymers Na4C60 and tetragonal C60.
2002 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, Vol. 65, no 15, 155421- p.Article in journal (Refereed) Published
We present a Raman investigation of the monoclinic two-dimensionally polymerized phase Na4C60 and a comparison with the pure tetragonal C60 polymer and the doped K3C60 structure. The Raman spectrum of Na4C60 depends on the probing laser wavelength, and high wave-number modes are hard to observe with a low-energy laser excitation. The spectrum for Na4C60 is very rich with a pronounced splitting of the original Hg modes and a large number of new modes. Several modes at low wave numbers support the presence of intermolecular bonds and the line broadening observed for low-frequency Hg modes is typical for electron-phonon coupling in metallic fullerene systems. From the shift of the pentagonal pinch mode we deduce an unexpectedly low charge transfer of approximately three electrons per C60 molecule. The presence of a distinct mode around 980 cm-1 throws doubts on earlier assumptions that modes in this range are connected to vibrations in the intermolecular cyclobutane rings found in C60 polymers. No superconductivity is observed in Na4C60, although the electron-phonon interaction derived from the Raman spectrum is similar to that in K3C60.
Place, publisher, year, edition, pages
American Physical Society , 2002. Vol. 65, no 15, 155421- p.
Condensed Matter Physics
Research subject Physics
IdentifiersURN: urn:nbn:se:umu:diva-20568DOI: 10.1103/PhysRevB.65.155421OAI: oai:DiVA.org:umu-20568DiVA: diva2:208981
ProjectsFullerenes, C60, fullerides, alkali metal doped fullerenes, fullerene compounds, two-dimensional polymer, structure, Raman spectroscopy, charge transfer, electron-phonon interaction