Observation of an exceptional point with an LR-shunted resonator

Non-Hermitian physical systems have enriched wave control abilities and dynamics of wave matter, especially around exceptional points (EPs). In this work, we theoretically, numerically, and experimentally studied an LR-shunted mechanical resonator for the observation of the exceptional point. The shunted resonator was composed of a mechanical resonator with a bonded piezoelectric patch and an LR-shunted circuit. A theoretical model for the LR-shunted resonator was first developed, and the exceptional point was identified from this theoretical model via a parameter space study. It was found that by varying the shunting circuit parameters, i.e., inductance and resistance, such a simple design supports the non-Hermitian degeneracy, namely the exceptional point. At the vicinity of the EP, the LR-shunted mechanical resonator had a square-root dependence on the external perturbation related to the nominal resistance. Next, we designed and fabricated a shunted resonator to verify our design through numerical analysis and experimental measurements. Moreover, our proposed LR-shunted resonator provides the possibility to dynamically encircle an exceptional point due to external stimuli. Our approach sheds light on the designs of chiral effect systems and dynamically tailoring losses in elasticity, and it enables alternative solutions for nondestructive structural health monitoring with enhanced sensitivity.