Hybrid-order topology of weak topological insulators

@article{Kooi2020HybridorderTO,
  title={Hybrid-order topology of weak topological insulators},
  author={Sander H. Kooi and Guido van Miert and Carmine Ortix},
  journal={Physical Review B},
  year={2020},
  volume={102},
  pages={041122}
}
We consider weak topological insulators with a twofold rotation symmetry around the dark direction, and show that these systems can be endowed with the topological crystalline structure of a higher-order topological insulator protected by rotation symmetry. These hybrid-order weak topological insulators display surface Dirac cones on all surfaces. Translational symmetry breaking perturbations gap the Dirac cones on the side surfaces leaving anomalous helical hinge modes behind. We also prove… 
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