Finite-size energy gap in weak and strong topological insulators

@article{Imura2012FinitesizeEG,
  title={Finite-size energy gap in weak and strong topological insulators},
  author={Ken-Ichiro Imura and Mayuko Okamoto and Yukinori Yoshimura and Yositake Takane and Tomi Ohtsuki},
  journal={Physical Review B},
  year={2012},
  volume={86},
  pages={245436}
}
The non-trivialness of a topological insulator (TI) is characterized either by a bulk topological invariant or by the existence of a protected metallic surface state. Yet, in realistic samples of finite size this non-trivialness does not necessarily guarantee the gaplessness of the surface state. Depending on the geometry and on the topological indices, a finite-size energy gap of different nature can appear, and correspondingly, exhibits various scaling behaviors of the gap. The spin-to… 
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