Electromechanical coupling effect in the detection of nanomechanical motion

The electromechanical coupling in the nanomechanical detection experiment is important as people forever pursue the higher sensitivity. In this work, we have studied theoretically the electromechanical coupling effect on the sensitivity of nanomechanical motion with the mixing current detection method under monostable and bistable regime, respectively. To obtain the sensitivity, the response function, the shot noise and the backaction noise with the coupling in the nanomechanical system consists of the oscillator coupled to a quantum dot are present. It is found that for the monostable state, the higher coupling means higher sensitivity. Both the contributions of shot noise and the backaction noise to the sensitivity are the decreasing function of the coupling. Once the system enters the bistability regime, the telegraph noise dominates instead of the resonance frequency noise, that due to the electron hopping in the bistable regime contributes more noise for the detection, its value is 3 orders of magnitude larger than the contribution of shot noise. As a result, one could find that there is a optimal value of the coupling corresponding to the phase transition point where the sensitivity is the best. Our results provide the pioneer and useful approach for the detection experiment. Graphic abstract