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Surface Hubbard U of alkali fullerides.

Macovez, R. and Hunt, M.R.C. and Goldoni, A. and Pedio, M. and Rudolf, P. (2011) 'Surface Hubbard U of alkali fullerides.', Journal of electron spectroscopy and related phenomena., 183 (1-3). pp. 94-100.


We report a combined photoemission spectroscopy (PES) and inverse photoemission spectroscopy (IPES) study of distilled, phase pure films of C60 and the monomeric fullerides Cs6C60, Cs4C60 and fcc RbC60. The separation between the highest energy PES and lowest energy IPES features, which is a measure of the barrier to hopping, is 1.45 eV in Cs4C60 and 0.7 eV in RbC60. This difference is large enough to explain, in a correlated electron picture, the reported differences in electronic mobility between the two stoichoimetries. From the PES-IPES energy separation, the value of the Hubbard U is estimated to be 1.5 eV in closed-shell C60 and Cs6C60, while in Cs4C60 and RbC60 such value is reduced to 1 and 0.7 eV, respectively. This trend can be only partially understood taking into account the different molecular polarizability and crystal structure of the various stoichiometries. The relatively low values found for open-shell compounds indicate that the bulk Hubbard U is smaller in open-shell fullerides than usually believed, which might help explain superconductivity and the observation of spin-singlets in odd-stoichiometry fullerides.

Item Type:Article
Keywords:Fullerenes, Fullerides, Hubbard U, Photoemission spectroscopy, Inverse photoemission spectroscopy.
Full text:(AM) Accepted Manuscript
Available under License - Creative Commons Attribution Non-commercial No Derivatives.
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Publisher statement:© 2010 This manuscript version is made available under the CC-BY-NC-ND 4.0 license
Date accepted:No date available
Date deposited:27 January 2016
Date of first online publication:January 2011
Date first made open access:No date available

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