Enhanced sensitivity in nonlinear parity-time symmetric silicon micromechanical resonators

Silicon resonant sensors are essential to a wide range of applications that involve the detection of pressure, acceleration, and magnetic fields. In general, they operate by monitoring a shift in the resonant frequency of silicon micromechanical resonators when subjected to perturbations due to the aforementioned parameters. This frequency shift manifests as a linear dependence on the perturbation. The demand for ever more precise silicon resonant sensors has catalyzed research endeavors aimed at boosting their sensitivity beyond geometrical constraints, including attempts to utilize synchronization phenomenon in coupled silicon resonators. Here we establish and experimentally demonstrate a method using non-Hermitian singularities, or exceptional points, to amplify sensitivity. This method reveals that the frequency shift in nonlinear parity-time symmetric silicon micromechanical resonators exhibits a cubic root singularity of perturbations. In the small perturbation limits, we observe an increase in sensitivity by several orders of magnitude when compared to traditional configurations. Our findings pave the way towards the next generation of ultrasensitive silicon resonant sensors.