The axion insulator is a higher-order topological insulator protected by inversion symmetry. We show that, under quenched disorder respecting inversion symmetry on average, the topology of the axion insulator stays robust, and an intermediate metallic phase in which states are delocalized is unavoidable at the transition from an axion insulator to a trivial insulator. We derive this conclusion from general arguments, from classical percolation theory, and from the numerical study of a 3D quantum network model simulating a disordered axion insulator through a layer construction. We find the localization length critical exponent near the delocalization transition to be ν = 1.42 ± 0.12. We further show that this delocalization transition is stable even to weak breaking of the average inversion symmetry, up to a critical strength. Finally, we also quantitatively map our quantum network model to an effective Hamiltonian and we find its low-energy k ∙ p expansion.
@article{osti_1852155,
author = {Song, Zhi-Da and Lian, Biao and Queiroz, Raquel and Ilan, Roni and Bernevig, B. Andrei and Stern, Ady},
title = {Delocalization Transition of a Disordered Axion Insulator},
annote = {The axion insulator is a higher-order topological insulator protected by inversion symmetry. We show that, under quenched disorder respecting inversion symmetry on average, the topology of the axion insulator stays robust, and an intermediate metallic phase in which states are delocalized is unavoidable at the transition from an axion insulator to a trivial insulator. We derive this conclusion from general arguments, from classical percolation theory, and from the numerical study of a 3D quantum network model simulating a disordered axion insulator through a layer construction. We find the localization length critical exponent near the delocalization transition to be ν = 1.42 ± 0.12. We further show that this delocalization transition is stable even to weak breaking of the average inversion symmetry, up to a critical strength. Finally, we also quantitatively map our quantum network model to an effective Hamiltonian and we find its low-energy k ∙ p expansion.},
doi = {10.1103/physrevlett.127.016602},
url = {https://www.osti.gov/biblio/1852155},
journal = {Physical Review Letters},
issn = {ISSN 0031-9007},
number = {1},
volume = {127},
place = {United States},
publisher = {American Physical Society (APS)},
year = {2021},
month = {06}}
USDOE Office of Science (SC); Schmidt Fund for Innovative Research; National Science Foundation (NSF); Gordon and Betty Moore Foundation; BSF Israel US Foundation; US Department of the Navy, Office of Naval Research (ONR)