Chalker-Coddington network model as a Floquet topological insulator

We re-examine the Chalker-Coddington network model, which was originally introduced to model integer quantum Hall plateau transitions. We point out that the dynamics of this model actually describe a periodically-driven (Floquet) system whose bands have vanishing Chern number throughout the phase diagram. Instead, the topological phase of the network model arises from a non-trivial dynamical Floquet invariant, i.e. the network model describes transitions between trivial and chiral Floquet phases of a distinct topological class from the integer quantum Hall effect. In view of this observation, we re-evaluate the standard arguments given in the past that the quantum Hall plateau transition and the transition in the Chalker-Coddington network model belong to the same universality class.