Topological Hofstadter insulators in a two-dimensional quasicrystal

We investigate the properties of a two-dimensional quasicrystal in the presence of a uniform magnetic field. In this configuration, the density of states (DOS) displays a Hofstadter-butterfly-like structure when it is represented as a function of the magnetic flux per tile. We show that the low-DOS regions of the energy spectrum are associated with chiral edge states, in direct analogy with the Chern insulators realized with periodic lattices. We establish the topological nature of the edge states by computing the topological Chern number associated with the bulk of the quasicrystal. This topological characterization of the nonperiodic lattice is achieved through a local (real-space) topological marker. This work opens a route for the exploration of topological-insulating materials in a wide range of nonperiodic lattice systems, including photonic crystals and cold atoms in optical lattices.