  The onset of the topological phase transition in a two-dimensional model for
a Chern Insulator, namely the Qi-Wu-Zhang(QWZ) model, is illustrated, with
particular emphasis on the appearance of chiral edge-modes. The edge-modes are
studied by analysing the dynamics of the edge-states in an equivalent model for
a one-dimensional charge pump, using a technique known as dimensional
extension. A further real-space analysis allows us to explain the onset of the
topological phase transition in terms of time-reversal symmetry breaking and to
quantitatively study the localisation of the edge-modes.
