Cooperative Jahn-Teller effect in a 2D mesoscopic Cn -60 system with D 5D symmetry adsorbed on buffer layers using Ising EFT model

M. Abou Ghantous, E. A. Moujaes, J. L. Dunn, A. Khater

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    Abstract

    Fullerene molecules adsorbed on surfaces often show macroscopic average distortions. As charged ions Cn -60 are known to be Jahn-Teller (JT) active, it is suggested that these distortions could be a manifestation of cooperative JT effects (CJTE) due to interactions between neighbouring fullerene ions. In order to understand the distortion properties it is necessary to take correlations between different distortions into account. However, this can't easily be done in the mean field approximation usually used to describe the CJTE. We therefore propose an alternative procedure to describe 2D mesoscopic islands of C60 ions in which a pseudo vector spin S is evoked to represent degenerate JT-distorted states when the quadratic JT coupling is considered. This approach is analogous to methods used for 2D magnetic systems. We then use the differential operator technique in effective field theory within the Ising approach. We include the effects of weak surface interactions and dynamic motion between equivalent distortions via terms equivalent to anisotropy and a transverse field in magnetism respectively. For distortions to D5d symmetry, we determine single site correlations as a function of temperature, the macroscopic average distortion describing a structural phase transition, and the isothermal response function. Phase diagrams are presented for relevant cases of the system parameters.

    Original languageEnglish
    Article number178
    JournalEuropean Physical Journal B
    Volume85
    Issue number6
    DOIs
    Publication statusPublished - 1 Jun 2012

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    ASJC Scopus subject areas

    • Electronic, Optical and Magnetic Materials
    • Condensed Matter Physics

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