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Fluctuation induced switching in nonequilibrium micromechanical oscillators


Under sufficiently large periodic drive, our micromechanical oscillators develop multistability and exhibit hysteresis in their frequency response. The presence of fluctuations enable the system to occasionally overcome the activation barrier and switch between the coexisting states. Unlike systems in thermal equilbrium, these oscillators are driven far from equilibrium and cannot be characterized by free energy. They possess certain properties that have no analog in equilbrium systems.

We have observed a number of generic features for switching. For instance, we measured two different scaling of the activation barrier close to the bifurcation points. When the oscillator is resonantly driven into bistability, the activation barrier varies with frequency detuning with critical exponent of 3/2, consistent with predicted universal scaling relationships for saddle node bifurcations. When the oscillator is driven into parametric resonance, the critical exponent becomes 2 as a different kind of bifurcation is involved.

We also explore critical kinetic phenomena that occur when the occupations of the two states are comparable. Within the narrow range of device parameters, the fluctuation spectrum exhibits a narrow peak. We have also demonstrated that the presence of noise leads to strong enhancements of the mixing of frequencies.

Publications:

Paths for fluctuation induced switching, H. B. Chan, M. I. Dykman and C. Stambaugh, Physical Review Letters 100, 130602 (2008).

Activation barrier scaling and crossover for noise-induced switching micromechanical parametric oscillators, H. B. Chan and C. Stambaugh, Physical Review Letters 99, 060601 (2007).

Supernarrow spectral peaks near a kinetic phase transition in a driven, nonlinear micromechanical oscillator, C. Stambaugh and H. B. Chan, Physical Review Letters 97, 110602 (2006).

Fluctuation-enhanced frequency mixing in a nonlinear micromechanical oscillator, H. B. Chan and C. Stambaugh, Physical Review B 73, 224301 (2006).

Noise activated switching in a driven, nonlinear micromechanical oscillator, C. Stambaugh and H. B. Chan, Physical Review B 73, 172302 (2006).

 

This work is supported by NSF DMR-0645448.

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