Exceptional points induced by unidirectional coupling in electronic circuits

Exceptional points in non-Hermitian systems have attracted considerable attention due to their novel applications in several fields such as optics, electronics, and mechanics. Typically, exceptional points are constructed through gain and loss modulation or dissipative coupling within the framework of parity-time symmetry or anti-parity-time symmetry. Recent demonstration of unidirectional coupling in optical resonators to create exceptional points has offered an alternative approach. This study extends this concept to electronic circuits, examining exceptional points that emerge in unidirectionally coupled LC circuits. We show that this circuit undergoes resonance frequency splitting that exhibits either linear or square-root scaling with the strength of the applied perturbation. We further explore the circuit’s scattering properties when connected to an input-output channel and demonstrate both theoretically and experimentally the splitting of transmission dips or peaks when a perturbation is applied—highlighting the potential for building sensors with enhanced sensitivity. This work not only deepens the understanding of exceptional points in electronic circuits but also encourages the exploration and application of non-Hermiticity in electronics. Exceptional points can be realized via engineering gain and loss or unidirectional coupling, as demonstrated in optical platforms. Here, the authors report an EP in unidirectionally coupled LC circuits and demonstrate a square-root scaling of frequency splitting with perturbation.