Structure-driven phase transitions in paracrystalline topological insulators

We study phase transitions driven by structural disorder in noncrystalline topological insulators. We introduce a procedural generation algorithm, the Perlin noise, typically used in computer graphics, to incorporate disorder to a two-dimensional lattice, allowing for a continuous interpolation between a pristine and a random lattice system, going through all different intermediate structural regimes, such as the paracrystalline and amorphous phases. We define a two-band model, including intraorbital and interorbital mixings, on the structures generated by the algorithm and we find a sequence of structure-driven topological phase transitions characterized by changes in the topological Bott index at which the insulating gap dynamically closes while evolving from the Bragg planes of the Brillouin zone towards the center. We interpret our results within the framework of Hosemann's paracrystal theory, in which distortion is included in the lattice structure factor and renormalizes the band-splitting parameter.