Berlin 2024 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 74: Topological Insulators

TT 74.8: Talk

Thursday, March 21, 2024, 17:00–17:15, H 3005

Structure-driven phase transitions in paracrystalline topological insulators — Victor Regis¹, Victor Velasco², Marcello Silva Neto^2,3, and •Caio Lewenkopf⁴ — ¹Jožef Stefan Institute, Ljubljana, Slovenia — ²Instituto de Física, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil — ³Laboratório Nacional de Nanotecnologia - CNPEM, Campinas, Brazil — ⁴Instituto de Física, Universidade Federal Fluminense, Niterói, Brazil

We study phase transitions driven by structural disorder in noncrystalline topological insulators. We use a procedural generation algorithm, the Perlin noise, typically used in computer graphics, to introduce disorder in a two-dimensional lattice, allowing a continuous interpolation between a pristine and a random gas system, going through all different intermediate structural regimes, such as the paracrystalline and the amorphous phases. We apply a two-band model, including intraorbital and interorbital mixings, to 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, according to which distortion is included in the lattice structure factor and renormalizes the band-splitting parameter. Based on these results, we ultimately demonstrate the phenomenon of topological protection at its extreme.

Keywords: topological phase transition; disordered systems; amorphous systems