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Joel Moser - Institut Catal´a de Nanotecnologia, Bellaterra, Spain

Dissipative nonlinearity in graphene mechanical resonators


Dissipative nonlinearity in graphene mechanical resonators

 

Graphene is a very interesting system for studying resonant mechanical behavior. It is the thinnest solid object imaginable, and partly because of this, it displays unusual mechanical phenomena. Among these, strong nonlinearities are ubiquitous. In this talk, I’ll present one striking manifestation of such a nonlinearity revealed when a graphene oscillator is driven to resonance : experimentally, the mechanical quality factor Q varies with the motional amplitude. To be more specific, Q goes up as the oscillation amplitude goes down. In particular, in the limit of extremely weak oscillations and at temperatures obtained in a dilution refrigerator, Q in graphene reaches very high values. This is rather surprising in light of the fact that Q, which measures the rate of mechanical energy loss, is constant in standard oscillators no matter how hard you drive them. To discuss the anomalous dissipation in graphene resonators, it is helpful to consider an equation of motion that features both a linear dissipation term that solely depends on velocity, and a nonlinear dissipation term that depends on both velocity and oscillation amplitude. I’ll compare the experimental variation of Q vs. the drive amplitude with the prediction obtained by solving this equation of motion. Finally, I’ll show the surprising result that strong nonlinear dissipation precludes mechanical bistability at large drive amplitude, a regime where standard oscillators would normally jump between a high and a low oscillation amplitude state.

 

Electronic address : moser.joel@gmail.com