Realization of merged topological bound states in the continuum in electric circuits

Abstract Topological bound states in the continuum (TBICs) have attracted the attention of researchers due to its characteristics that combine those of BIC and topological states. In this letter, we investigate a mirror-stacked bilayer doubled chain coupled SSH model. Specifically, by adjusting the interlayer coupling, the eigenstates of the single layer counterpart shift without hybridization, resulting in two intriguing phenomena: the merged TBICs (MTBICs) as well as the coexistence of TBIC and in-gap topological states. Through the circuit model, we experimentally observed the above-mentioned two phenomena, meanwhile found that MTBIC has enhanced localization and improved robustness than conventional BIC. Our work demonstrates the potential of topological circuits in realizing BICs. Furthermore, it offers insights that could inform future research endeavors and device design in the field of BIC.