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 π-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 up to 100%.