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Genuine Topological Anderson Insulator from Impurity Induced Chirality Reversal
Avedis Neehus1,2, Frank Pollmann1,2, Johannes Knolle1,2,3
1Technical University of Munich, Physics Department, TUM School of Natural Sciences, 85748 Garching, Germany.
Physical Review Letters
|October 5, 2025
Summary
We discovered that tuning mass impurities in Dirac fermions can reverse topological properties, creating a novel topological Anderson insulator phase. This phase is distinct from clean topological insulators and emerges from impurity resonances.
Area of Science:
- Condensed matter physics
- Topological materials
- Quantum phenomena
Background:
- Dirac fermions are fundamental particles in condensed matter physics.
- Topological insulators possess unique electronic properties due to their band structure.
- Mass impurities can significantly alter material properties.
Purpose of the Study:
- Investigate the impact of mass impurities on Dirac fermions.
- Explore the creation of topological gaps and phase transitions.
- Characterize a novel impurity-induced topological phase.
Main Methods:
- T-matrix expansion for theoretical analysis.
- Large-scale Chebyshev-polynomial Green's function numerics.
- Modeling Dirac fermions with mass impurities.
Main Results:
- Mass impurities open a global topological gap in Dirac fermions.
- Chirality (Chern number sign) is reversible by tuning impurity scattering.
- A genuine topological Anderson insulator phase is induced, disconnected from the clean limit.
- A tricritical point exists at zero impurity density, linked to a zero-energy bound state in the continuum.
Conclusions:
- Disorder-induced topological phases can be fundamentally different from clean systems.
- Mass disorder is not always an irrelevant perturbation for Dirac semimetals.
- The findings suggest new avenues for engineering topological materials and devices.
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