High-T C superconductivity in Cs3C60 compounds governed by local Cs-C60 Coulomb interactions

Document Type

Article

Publication Date

3-2-2017

Abstract

Unique among alkali-doped A 3C60 fullerene compounds, the A15 and fcc forms of Cs3C60 exhibit superconducting states varying under hydrostatic pressure with highest transition temperatures at = 38.3 and 35.2 K, respectively. Herein it is argued that these two compounds under pressure represent the optimal materials of the A 3C60 family, and that the C60-associated superconductivity is mediated through Coulombic interactions with charges on the alkalis. A derivation of the interlayer Coulombic pairing model of high-T C superconductivity employing non-planar geometry is introduced, generalizing the picture of two interacting layers to an interaction between charge reservoirs located on the C60 and alkali ions. The optimal transition temperature follows the algebraic expression, T C0 = (12.474 nm2 K)/ℓζ, where ℓ relates to the mean spacing between interacting surface charges on the C60 and ζ is the average radial distance between the C60 surface and the neighboring Cs ions. Values of T C0 for the measured cation stoichiometries of Cs3-xC60 with x ≈ 0 are found to be 38.19 and 36.88 K for the A15 and fcc forms, respectively, with the dichotomy in transition temperature reflecting the larger ζ and structural disorder in the fcc form. In the A15 form, modeled interacting charges and Coulomb potential e2/ζ are shown to agree quantitatively with findings from nuclear-spin relaxation and mid-infrared optical conductivity. In the fcc form, suppression of TCMeas below T C0 is ascribed to native structural disorder. Phononic effects in conjunction with Coulombic pairing are discussed.

Identifier

85014967729 (Scopus)

Publication Title

Journal of Physics Condensed Matter

External Full Text Location

https://doi.org/10.1088/1361-648X/aa5dbd

e-ISSN

1361648X

ISSN

09538984

PubMed ID

28151430

Issue

14

Volume

29

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