High Sensitivity of Parity Time Symmetric Piezoelectric Resonator Systems at Exceptional Point

Piezoelectric resonance sensors, which measure the mass of absorbed materials by detecting the resonance frequency, have wide applications. In this paper, a parity time (PT) symmetric system is presented to improve the sensitivity of piezoelectric resonance sensor. The PT symmetric system exhibits an exceptional point (EP) as the eigenvalues change from complex to real, and the eigenvalues and corresponding eigenstates split up simultaneously. High sensitivity of frequency splitting to small perturbation at EP has important applications in resonance sensing systems. The EP is observed in the PT symmetric system of a piezoelectric resonator coupled with an LCR circuit in this work. With sufficiently small perturbation, the sensitivity of the PT system is ultra-enlarged compared with a traditional resonance sensor. Both theoretical analysis and experimental variation are performed with a humidity sensing system.