Observation of Boundary‐Obstructed Topological Insulators in 2D Asymmetric Su–Schrieffer–Heeger Topological Electric Circuits

Topological insulators that support unique symmetry‐protected boundary states gain popularity in the field of electric circuit systems. Boundary‐obstructed topological (BOT) insulators, as a new class of topological insulators, do not utilize the closure of the bulk band during the topological phase transition, which displays as an obstruction of boundary states. In this work, the experimental realization of BOT insulators based on electric circuit systems are reported and it is further demonstrated experimentally that the corresponding hollow structure consisting of only edges and corners can offer corner states in the edge gap. In this research, a highly controllable platform is offered for investigating unique topological phenomena and the way is paved for observing boundary‐obstructed topology by electric circuit systems. The existence of boundary‐obstructed topology corner states in an electric circuit based on the asymmetric 2D Su‐Schrieffer‐Heeger model is demonstrated by numerical calculation and experimental realization. Furthermore, the existence of corner states in the corresponding hollow structure, which consists only of edges and corners, is also shown via the electric circuit.