Strong negative nonlinear friction from induced two-phonon processes in vibrational systems
Strong negative nonlinear friction from induced two-phonon processes in vibrational systems
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DOI：
10.1038/s41467-018-05246-w
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发表时间：
2018-08-13
影响因子：
16.6
通讯作者：
Chan, H. B.
中科院分区：
文献类型：
--
作者：
Dong, X.;Dykman, M. I.;Chan, H. B.
从激光器到时钟再到生物系统的系统中的自持振动通常与线性摩擦系数有关，线性摩擦系数将摩擦力与速度联系起来，变为负值。振动振幅的失控是由正的非线性摩擦，迅速增加的振幅。在这里，我们使用调制的机电谐振器表明，非线性摩擦可以被制成负的，并足够强，以克服在大的振动振幅的正线性摩擦。该实验涉及应用驱动器，同时激发两个声子的研究模式和一个声子的一个更快的衰减高频模式。研究了具有负非线性摩擦的振子动力学的一般特征。值得注意的是，在这种情况下，振荡器的自持振动需要激活。此外，当施加共振力时，可以出现大振幅强迫振动的分支，其与普通小振幅响应的分支隔离。
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. 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 require activation 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.