Bound state in the continuum in topological inductor-capacitor circuit

Bound states in the continuum (BICs) have received increasing attention from researchers because of their potential applications in photonic crystal fibers, as well as in lasing, sensing, and surface acoustic wave devices. BICs have been experimentally observed in acoustic resonators, photonic crystal slabs, and optical waveguides. Herein, we constructed a topological inductor-capacitor (LC) circuit to observe BICs; the circuit consists of two identical LC Su-Schrieffer-Heeger chains coupled using a middle chain with capacitors. In addition, a BIC in a non-Hermitian system was also experimentally observed by adding different resistances to the original LC circuit. Our experimental and simulation results thus prove that an electrical circuit could be used as a platform to realize BIC. Furthermore, we believe that such a circuit can be extended to two- and three-dimensional models and higher frequencies, making it suitable for electrical device applications, such as antennae, filters, and radio frequency devices.