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Ordered low-temperature structure in K4C60 detected by infrared spectroscopy

K. Kamaras·G. Klupp·D. B. Tanner·A. F. Hebard·N. M. Nemes·J. E. Fischer
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Abstract

Infrared spectra of a K4C60 single-phase thin film have been measured between room temperature and 20 K. At low temperatures, the two high-frequency T1u modes appear as triplets, indicating a static D2h crystal-field stabilized Jahn-Teller distortion of the (C60)4- anions. The T1u(4) mode changes into the known doublet above 250 K, a pattern which could have three origins: a dynamic Jahn-Teller effect, static disorder between "staggered" anions, or a phase transition from an orientationally-ordered phase to one where molecular motion is significant.

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K. Kamaras, G. Klupp, D. B. Tanner, A. F. Hebard, N. M. Nemes, J. E. Fischer. 2001-10-16. Ordered low-temperature structure in K4C60 detected by infrared spectroscopy. https://doi.org/10.1103/physrevb.65.052103

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