Strong negative nonlinear friction from induced two-phonon processes in vibrational systems

TL;DR

This paper demonstrates that negative nonlinear friction, induced via two-phonon processes in a modulated electromechanical resonator, can lead to self-sustained vibrations and isolated vibrational branches, with potential sensing applications.

Contribution

It introduces a method to achieve negative nonlinear friction through two-phonon processes, enabling control over vibrational states in resonators.

Findings

Negative nonlinear friction can overcome positive linear friction at large amplitudes.

Self-sustained vibrations are activated by negative nonlinear friction.

Isolated vibrational branches emerge under resonant forcing.

Abstract

Self-sustained vibrations in systems ranging from lasers to clocks to biological systems are often associated with the coefficient of linear friction, which relates the friction force to the velocity, becoming negative [1,2]. The runaway of the vibration amplitude is prevented by positive nonlinear friction that increases rapidly with the amplitude. Here we use a modulated electromechanical resonator to show that nonlinear friction can be made negative and sufficiently strong to overcome positive linear friction at large vibration amplitudes. The experiment involves applying a drive that simultaneously excites two phonons of the studied mode and a phonon of a faster decaying high-frequency mode. We study generic features of the oscillator dynamics with negative nonlinear friction. Remarkably, self-sustained vibrations of the oscillator need to be activated in this case. When, in addition, a resonant force is applied, a branch of large-amplitude forced vibrations can emerge, isolated from the branch of the ordinary small-amplitude response. Isolated branches of self-sustained and forced vibrations are advantageous for applications in sensing and control.