• DOI:10.1103/PhysRevX.3.021018
• Corpus ID: 118603811

Topological kink states at a tilt boundary in gated multi-layer graphene

@article{Vaezi2013TopologicalKS,
  title={Topological kink states at a tilt boundary in gated multi-layer graphene},
  author={Abolhassan Vaezi and Yufeng Liang and D. H. Ngai and Li Yang and Eun-Ah Kim},
  journal={arXiv: Mesoscale and Nanoscale Physics},
  year={2013}
}

• A. Vaezi, Yufeng Liang, +2 authors Eun-Ah Kim
• Published 8 January 2013
• Physics
• arXiv: Mesoscale and Nanoscale Physics

The search for new realization of topologically protected edge states is an active area of research. We show that a tilt boundary in gated multi-layer graphene supports topologically protected gapless kink states, associated with quantum valley Hall insulator (QVH). We investigate such kink states from two perspectives: the microscopic perspective of a tight-binding model and an ab-initio calculation on bilayer, and the perspective of symmetry protected topological (SPT) states for general multi-layer. We show that a AB-BA bilayer tilt boundary supports gapless kink states that are undeterred by strain concentrated at the boundary. Further, we establish the kink states as concrete examples of edge states of {\it time-reversal symmetric} ${\mathbb Z}$-type SPT, protected by no valley mixing, electron number conservation, and time reversal $T$ symmetries. This allows us to discuss possible phase transitions upon symmetry changes from the SPT perspective. Recent experimental observations of a network of such tilt boundaries suggest that transport through these novel topological kink states might explain the long standing puzzle of sub-gap conductance. Further, recent observation of gap closing and re-opening in gated bi-layer might be the first example of a transition between two distinct SPT's: QVH and LAF.