### arXiv:2003.09936 [cond-mat.mes-hall]AbstractReferencesReviewsResources

#### Engineering Corner States from Two-Dimensional Topological Insulators

Yafei Ren, Zhenhua Qiao, Qian Niu

Published 2020-03-22Version 1

We theoretically demonstrate that the second-order topological insulator with robust corner states can be realized in two-dimensional $\mathbb{Z}_2$ topological insulators by applying an in-plane Zeeman field. Zeeman field breaks the time-reversal symmetry and thus destroys the $\mathbb{Z}_2$ topological phase. Nevertheless, it respects some crystalline symmetries and thus can protect the higher-order topological phase. By taking the Kane-Mele model as a concrete example, we find that spin-helical edge states along zigzag boundaries are gapped out by Zeeman field whereas in-gap corner state at the intersection between two zigzag edges arises, which is independent on the field orientation. We further show that the corner states are robust against the out-of-plane Zeeman field, staggered sublattice potentials, Rashba spin-orbit coupling, and the buckling of honeycomb lattices, making them experimentally feasible. Similar behaviors can also be found in the well-known Bernevig-Hughes-Zhang model.

**Categories:**cond-mat.mes-hall