Theoretical Fermi-Surface Properties and Superconducting Parameters for K3C60

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Science  08 Nov 1991:
Vol. 254, Issue 5033, pp. 842-845
DOI: 10.1126/science.254.5033.842


Quantitative theories of superconductivity in alkali-doped C60 require an accurate and detailed description of the Fermi surface. First-principles calculations of Fermi-surface properties and electronic parameters for K3C60, the prototype fulleride-superconductor, are reported. The Fermi surface has two sheets; the first is free-electron-like, and the second is multiply-connected, forming two interlocked symmetry-equivalent pieces that never touch. The calculated (clean limit) London penetration depth is Λ = 1600 Å. Comparing the Fermi velocity with the experimental coherence length leads to a superconducting pairing strength λ ∼ 5, indicating very strong coupling. Partial nesting in the second Fermi-surface sheet may favor coupling to short-wavelength q,0,0 optic modes.