Controlling edge states in the Kane-Mele model via edge chirality

We investigate the dependence of band dispersion of the quantum spin Hall effect (QSHE) edge states in the Kane-Mele model on crystallographic orientation of the edges. Band structures of the one-dimensional honeycomb lattice ribbons show the presence of the QSHE edge states at all orientations of the edges given sufficiently strong spin-orbit interactions. We find that the Fermi velocities of the QSHE edge-state bands increase monotonically when the edge orientation changes from zigzag (chirality angle theta = 0 degrees) to armchair (theta = 30 degrees). We propose a simple analytical model to explain the numerical results. (C) 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim