Buckled honeycomb antimony: Higher order topological insulator and its relation to the Kekulé lattice
Santosh Kumar Radha, Walter R. L. Lambrecht
Abstract
Higher order topological tnsulators are $d$-spatial dimensional systems featuring topologically protected gapless states at their $(d\ensuremath{-}n)$-dimensional boundaries. With the help of ab initio calculations and tight-binding models along with symmetry considerations, we show that monolayer buckled honeycomb structures of group-V elements (Sb, As), which have already been synthesized, belong in this category and have a spinless charge fractionalization of $\frac{e}{2}$ at the corner states as well as weak topological edge states, protected by the ${S}_{6}$ symmetry operation, which classify this system as a quadrupole topological insulator. The robustness of these edge and corner states to perturbations is explicitly demonstrated.