Regensburg 2025 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 4: Topological Insulators

TT 4.8: Talk

Monday, March 17, 2025, 11:30–11:45, H33

Genuine topological Anderson insulator from impurity induced chirality reversal — •Avedis Neehus, Frank Pollmann, and Johannes Knolle — Technical University of Munich, TUM School of Natural Sciences, Physics Department, 85748 Garching, Germany

We investigate a model of Dirac fermions with topological mass impurities which open a global topological gap even in the dilute limit. Surprisingly, we find that the chirality of this mass term, i.e., the sign of the Chern number, can be reversed by tuning the magnitude of the single-impurity scattering. Consequently, the disorder induces a phase disconnected from the clean topological phase, i.e., a genuine topological Anderson insulator. In seeming contradiction to the expectation that mass disorder is an irrelevant perturbation to the Dirac semimetal, the tri-critical point separating these two Chern insulating phases and a thermal metal phase is located at zero impurity density and connected to the appearance of a zero energy bound state in the continuum corresponding to a divergent topological mass impurity. Our conclusions based on the T-matrix expansion are substantiated by large scale Chebyshev-Polynomial-Green-Function numerics. We discuss possible experimental platforms.

Keywords: Disorder; Topology; Transport; Chebychev