We observed distinct interlayer shear mode Raman spectra for trilayer graphene with ABA and ABC stacking order. There are two rigid-plane shear-mode phonon branches in trilayer graphene. We found that ABA trilayers exhibit pronounced Raman response from the high-frequency shear branch, without any noticeable response from the low-frequency branch. In contrast, ABC trilayers exhibit no response from the high-frequency shear branch, but significant Raman response from the low-frequency branch. Such complementary behaviors of Raman shear modes can be explained by the distinct symmetry of the two trilayer allotropes. The strong stacking-order dependence was not found in the layer-breathing modes, and thus represents a unique characteristic of the shear modes.
@article{arxiv.1405.7343,
title = {Stacking-dependent shear modes in trilayer graphene},
author = {Chun Hung Lui and Zhipeng Ye and Courtney Keiser and Eduardo B. Barros and Rui He},
journal= {arXiv preprint arXiv:1405.7343},
year = {2015}
}