Bound states in the continuum of three-leg ladder topoelectrical circuits

Bound States in the Continuum (BICs) represent a distinct category of localized states with eigenvalue embeddings within extended states, maintaining strong localization and a high Q factor without hybridization. In this study, we introduce a topological inductor–capacitor circuit constructed using a three-leg ladder lattice model and provide experimental evidence of the existence of the BICs. Furthermore, we confirm that the properties of the system's BICs are derived from the separated subspace Hamiltonian and can be adjusted by manipulating the parameters of the subspace. We investigated the impact of non-Hermitian perturbations on BICs by introducing small resistances, and the results demonstrate that BICs exhibit resistance to non-Hermitian perturbations. Our work validates the potential of topological circuits for realizing BICs, and we anticipate its extension to higher-dimensional and higher-frequency circuits, enabling applications in sensors, filters, and radio frequency devices.