Charging of Majorana edge modes caused by interaction: Exact results

The ground-state behavior of a spinless fermion chain with pairing (the Kitaev chain) and an interaction between fermions at neighboring sites is studied for free open boundaries. Using the exact quantum solution, it has been shown that there can exist boundary bound states for many values of the interaction. The interaction produces charging of the vacua of the model and charging of the boundary bound states. The theory also describes the behavior of an XYZ spin-1/2 chain with free open edges.