  We report a confocal Raman study on edges of single layer graphene. It is
found that edge orientations could be identified by G mode besides D mode. We
observe that G mode at edges of single layer graphene exhibits polar behaviors
and different edges like zigzag- or armchair-dominated responses differently to
the polarization of the incident laser. Moreover, G mode shows stiffening at
zigzag-dominated edges, while it is softened at armchair- dominated ones. Our
observations are in good agreement with recent theory (K. Sasaki, et al., J.
Phys. Soc. Jpn. 79, 044603) and could be well explained by the unique
properties of pseudospin at graphene edges, which lead to asymmetry of Raman
active modes and non-adiabatic processes (Kohn Anomaly) at different types of
edges. This work could be useful for further study on the properties of
graphene edge and development of graphene-based devices.
