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Optical properties of the alkali-metal-doped superconducting fullerenes: K3C60 and Rb3C60

L. Degiorgi, E. J. Nicol, O. Klein, G. Grüner, P. Wachter, S.-M. Huang, J. Wiley, R. B. Kaner

DOI 10.1103/PhysRevB.49.7012 · Physical Review B

T1

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Abstract

We have measured the optical reflectivity over a broad spectral range of single-phase K3C60 and Rb3C60 compounds, and have evaluated the optical conductivity both below and above the superconducting transition temperature. We identify various features in the excitation spectrum of the normal state: a Drude contribution at low frequency, a midinfrared absorption, and several interband transitions. In the superconducting state our results are in full agreement with a BCS singlet ground state, with the measured gap values consistent with the weak-coupling limit. We also evaluate several intrinsic parameters characterizing both the normal and superconducting state, such as the plasma frequency, the relaxation scattering rate, and the mean free path, besides the superconducting gaps and the penetration depth. We compare these quantities with similar ones from other experiments and find satisfactory agreement. Moreover, we present our calculation of the electrodynamic response above and below Tc with the standard Eliashberg electron-phonon theory of superconductivity, which strongly supports a pairing mechanism mediated by high-frequency intramolecular phonon modes.

Source-reported materials — not catalogue approval

FormulaReported Tc (K)Pressure (GPa)Type
K3C60

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19Pressure not reportedunknown
Rb3C60

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Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.

29Pressure not reportedunknown
K3C60

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Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.

19.8Pressure not reportedonset

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