Majorana modes and complex band structure of quantum wires

We describe Majorana edge states of a semi-infinite wire using the complex band structure approach. In this method the edge state at a given energy is built as a superposition of evanescent waves. It is shown that the superposition can not always satisfy the required boundary condition, thus restricting the existence of edge modes. We discuss purely 1D and 2D systems, focusing in the latter case on the effect of the Rashba mixing term.