Topological Electronic States of 2D HexNet

Recently, the two-dimensional (2D) hexagonal network (HexNet) structures have been synthesized based on the hydrogen-bonded buckybowled sheet. The remarkable feature of 2D HexNet system has a double-decker structure, where two lattice networks are mutually woven. In this paper, we shall focus on exploring the electronic and topological properties of the 2D HexNet system. In the conventional HexNet system, each molecule forms hydrogen bonds with six neighboring molecules, allowing for an approximation of 2D HexNet as a double-decker 2D tight-binding network with six coordination (HexNet-6). This configuration fi guration exhibits characteristics of a nodal line semimetal, explained by parity analysis in momentum space. In contrast, the HexNet with a three-coordinate structure (HexNet-3), presents six Dirac points and a nontrivial Zak phase of pi , leading to the emergence of topological edge states, shedding light on its unique electronic behavior.