Observation of exceptional points and realization of high sensitivity sensing in electric circuits

We explore the parity-time (PT)-symmetry breaking transition in a dimer circuit composed of two RLC resonators that are weakly coupled via an inductor. The energy behavior of this dimer circuit is reflected in the splitting or degeneracy of the systems eigenfrequencies as the gain–loss strength varies. Its dynamical properties can be described by a non-Hermitian Hamiltonian. The eigenfrequency spectrum of the system is divided by two critical points into three distinct regions: the symmetric region, the oscillatory growth region, and the fully exponential growth region. Building upon previous work on implementing the exceptional point (EP) in circuit systems, our study focuses on further exploring the variation patterns of circuit eigenfrequencies near the EP under weak coupling conditions. In addition, we construct a corresponding Dirac point (DP) circuit system for comparison. By leveraging the unique physical properties near both the EP and the DP, we further propose potential practical applications. Using perturbation theory and system simulations, we demonstrate that the square-root eigenfrequency splitting near the EP significantly enhances the sensitivity to small external perturbations, compared to the linear splitting behavior near the DP. This study presents promising prospects for next-generation sensing technologies.