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HL: Fachverband Halbleiterphysik

HL 46: Poster 2

HL 46.3: Poster

Donnerstag, 29. März 2007, 15:00–17:30, Poster A

Infrared spectroscopy on rotor-stator compounds C₆₀-C₈H₈ and C₇₀-C₈H₈ under pressure — •K. Thirunavukkuarasu¹, C.A. Kuntscher¹, Gy. Bényei², I. Jalsovszky², G. Klupp³, K. Kamarás³, É Kováts³, and S. Pekker³ — ¹Experimentalphysik II, Universität Augsburg, D-86159 Augsburg, Germany — ²Department of Organic Chemistry, Eötvös Loránd University, P.O.Box 32, Budapest, Hungary H 1518 — ³Research Institute for Solid State Physics and Optics, Hungarian Academy of Sciences, P.O.Box 49, Budapest, Hungary H 1525

The fullerene-cubane molecular crystals C₆₀-C₈H₈ and C₇₀-C₈H₈ are the first members of the rotor-stator crystal family [1]. Static C₈H₈ molecules occupy the octahedral voids of the fullerene fcc structure and act as bearings for the rotating fullerene molecules. On cooling, C₆₀-C₈H₈ undergoes an orientational ordering phase transition at 140 K, while C₇₀-C₈H₈ undergoes transitions at around 390 K and 150 K. Under pressure C₆₀-C₈H₈ shows orientational ordering at 0.8 GPa [2]. We performed further pressure-dependent transmittance measurements on both C₆₀-C₈H₈ and C₇₀-C₈H₈ molecular crystals over a broad frequency range (FIR-VIS), for pressures up to 10 GPa. The pressure-induced changes in the vibrational modes of the fullerene and cubane molecules and the shift of the band gap are reported.

Supported by the DFG.

[1] S. Pekker et al., Nature Materials 4, 764 (2005).

[2] C. A. Kuntscher et al., Phys. Stat. Sol. (b) 243, 2981 (2006).