Structurally Dependent Fano Resonances in the Infrared Spectra of   Phonons in Few-Layer Graphene
  The in-plane optical phonons around 200 meV in few-layer graphene are investigated utilizing infrared absorption spectroscopy. The phonon spectra exhibit unusual asymmetric features characteristic of Fano resonances, which depend critically on the layer thickness and stacking order of the sample. The phonon intensities in samples with rhombohedral (ABC) stacking are significantly higher than those with Bernal (AB) stacking. These observations reflect the strong coupling between phonons and interband electronic transitions in these systems and the distinctive variation in the joint density of electronic states in samples of differing thickness and stacking order. 
Zhiqiang Li, Chun Hung Lui, Emmanuele Cappelluti, Lara Benfatto, Kin   Fai Mak, G. Larry Carr, Jie Shan and Tony F. Heinz
cond-mat.mes-hall