Nonlinearities are inherent to the dynamics of two-dimensional materials. Phenomena-like intermodal coupling already arise at amplitudes of only a few nanometers, and a range of unexplored effects still awaits to be harnessed. Here, we demonstrate a route for generating mechanical frequency combs in graphene resonators undergoing symmetry-breaking forces. We use electrostatic force to break the membrane’s out-of-plane symmetry and tune its resonance frequency toward a one-to-two internal resonance, thus achieving strong coupling between two of its mechanical modes. When increasing the drive level, we observe splitting of the fundamental resonance peak, followed by the emergence of a frequency comb regime. We attribute the observed physics to a nonsymmetric restoring potential and show that the frequency comb regime is mediated by Neimark bifurcation of the periodic solution. These results demonstrate that mechanical frequency combs and chaotic dynamics in 2D material resonators can emerge near internal resonances due to symmetry-breaking.

中文翻译：

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石墨烯谐振器中的对称断裂诱导频率梳

非线性是二维材料动力学所固有的。类似现象的联运耦合已经出现在只有几纳米的幅度上，并且一系列未探索的效应仍有待利用。在这里，我们展示了在承受对称破坏力的石墨烯谐振器中产生机械频率梳的途径。我们使用静电力打破膜的平面外对称性，并将其共振频率调整为一对二的内部共振，从而实现其两种机械模式之间的强耦合。当增加驱动电平时，我们观察到基本共振峰的分裂，然后出现频率梳状态。我们将观察到的物理归因于非对称恢复势，并表明频率梳状态是由周期解的内马克分岔介导的。这些结果表明，由于对称性破坏，二维材料谐振器中的机械频率梳和混沌动力学可以出现在内部谐振附近。