The spin-orbit interaction enhanced terahertz absorption in graphene around the K point

We present a quantitative analysis on the effect of the spin-orbit interaction in the optical absorption of pi-electrons in graphene. It has been shown that the optical absorption amplitude of graphene around the K point in the Brillouin zone has a node in the two-dimensional Brillouin zone of honeycomb lattice. We calculated the k-dependent absorption matrix by taking into account the finite spin-orbit interaction in graphene. It was found that the spin-orbit interaction lifts the nodes in the absorption matrix. Furthermore, in the terahertz frequency regime, the spin-orbit interaction can significantly enhance the optical absorption in graphene, by LIP to 100%. Crown Copyright (C) 2008 Published by Elsevier Ltd. All rights reserved.