Beyond the linear and Duffing regimes in nanomechanics: Circularly polarized mechanical resonances of nanocantilevers

We present here an experimental and theoretical study of the nonlinear coupling between the two polarizations of the mechanical resonances of singly clamped nanowires and nanotubes, leading to circularly polarized oscillations. This regime exists for high amplitudes and beyond the frequency range of the "classical" Duffing regime. Good quantitative agreement is found with a simple theoretical model based on the first nonlinear terms of the coupling. The assumptions used in the model are quite general and thus the circular movement is a universal response for nanocantilevers.