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arXiv · 1412.8538

π-Plasmon Dispersion in Free-Standing Graphene by Momentum-Resolved Electron Energy-Loss Spectroscopy

S. C. Liou·C. -S. Shie·C. H. Chen·R. Breitwieser·W. W. Pai·G. Y. Guo·M. -W. Chu
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Abstract

The π-plasmon dispersion in graphene was scrutinized by momentum(q)-resolved electron energy-loss spectroscopy with an improved q resolution and found to display the square root of q dispersion characteristic of the collective excitation of two-dimensional electron systems, in contrast with previous experimental and theoretical studies which reported a linear q dispersion. Our theoretical elaborations on the q-dependent spectra affirm this square root of q relation and further unveil an in-plane electronic anisotropy. The physical property of the π plasmon is thoroughly compared to that of the two-dimensional plasmon due to carriers of the Dirac fermions. A clear distinction between the π plasmon and the two-dimensional Dirac plasmon was demonstrated, clarifying the common notion on correlating the linearly-dispersed Dirac cones to the linear dispersion of the π plasmon previously reported.

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S. C. Liou, C. -S. Shie, C. H. Chen, R. Breitwieser, W. W. Pai, G. Y. Guo, M. -W. Chu. 2014-12-30. π-Plasmon Dispersion in Free-Standing Graphene by Momentum-Resolved Electron Energy-Loss Spectroscopy. https://doi.org/10.1017/s1431927614010678

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