Realizations of Su-Schrieffer-Heeger (SSH) edge states in two-dimensional hydrocarbon systems

The Su-Schrieffer-Heeger (SSH) model of one-dimensional (1D) diatomic and four-atom chains, exhibit a topological phase transition characterized by the Zak phase. However, a challenge arises from the inherent difficulty of maintaining strong structural stability in real 1D nanostructures. Here, we show how to realize periodic 1D chains, reminiscent of the SSH model, in a two-dimensional (2D) system. These chains form a quasi-1D chain topological insulator (CTI) where the interchain coupling can be neglected. Based on first-principles calculations, we proposed that such CTIs can be realized in dumbbell (DB) C40H14 and DB C40H12 monolayers. The monolayers are CTIs, with a type of weak topological state, and the topological phase transition can be achieved by unit cell transformation or the application of 2D strain. Furthermore, increasing the number of DB C10H4 rings can enlarge the distance between the chains, corresponding to line defects within the monolayer, providing a possible strategy for experimental synthesis.