Metal-to-insulator evolution in (NH3)xNaK2C60: an NMR study

M. Ricco; G. Fumera; T. Shiroka; O. Ligabue; C. Bucci; F. Bolzoni

doi:10.1103/PhysRevB.68.035102

Metal-to-insulator evolution in (NH3)xNaK2C60: an NMR study

Strongly Correlated Electrons 2009-11-10 v1 Superconductivity

Authors: M. Ricco , G. Fumera , T. Shiroka , O. Ligabue , C. Bucci , F. Bolzoni

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Abstract

A singular evolution toward an insulating phase, shown by 23Na and 13C NMR, has been observed in the superconducting fullerides (NH3)xNaK2C60 for x>1. Unlike most common cases, this insulating phase is non magnetic and 13C spin lattice relaxation shows the presence of a spin gap. These two features suggest that a charge disproportion from C60^(3-) to C60^(2-) and C60^(4-) can drive the system from the metallic to the insulating state. The restoring of the Na+ cation in the center of the octahedral interstice in the insulating phase, as indicated by 23Na and 2H lineshape analysis, confute the current belief that the cation off-centering is effective in quenching the superconductivity.

Keywords

metal-insulator transition fullerides NMR study spin gap charge disproportionation

Cite

@article{arxiv.cond-mat/0305166,
  title  = {Metal-to-insulator evolution in (NH3)xNaK2C60: an NMR study},
  author = {M. Ricco and G. Fumera and T. Shiroka and O. Ligabue and C. Bucci and F. Bolzoni},
  journal= {arXiv preprint arXiv:cond-mat/0305166},
  year   = {2009}
}

Comments

7 pages, 5 figures. To be published in Phys. Rev. B

Metal-to-insulator evolution in (NH3)xNaK2C60: an NMR study

Abstract

Keywords

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