Quantum Spin Hall effect on planar Archimedean lattices

Abstract: Archimedean lattices constitute a unique family of two-dimensional tilings formed from regular polygons arranged with uniform vertex configurations. While the kagome lattice has been extensively studied and the snub square lattice has served as a quasicrystal approximant, the broader family remains comparatively unexplored in the context of electronic and topological properties. In this work, we present a systematic tight-binding study of all eight pure Archimedean lattices, incorporating both $s$ and $p$ orbitals. We analyze their band structures, investigate topological edge states arising from unconventional nanoribbon geometries, and evaluate $\mathbb{Z}_2$ invariants as well as intrinsic spin Hall conductivities using the Kubo formalism. Our results reveal that several Archimedean lattices, such as the truncated hexagonal and truncated trihexagonal lattices, host nearly dispersionless flat bands extending across the Brillouin zone, which remain robust even in the presence of next-nearest-neighbor hopping and strong spin-orbit coupling. In particular, the truncated trihexagonal lattice supports topologically protected, highly spin-polarized edge states across multiple ribbon geometries. These states are stable against defects and spin-flip scattering, and they give rise to sizable spin Hall currents.