Spontaneous Exact Spin-Wave Fractals in Magnonic Crystals.
Spontaneous Exact Spin-Wave Fractals in Magnonic Crystals.
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DOI：
10.1103/physrevlett.121.107204
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发表时间：
2018-05
影响因子：
8.6
通讯作者：
D. Richardson;B. Kalinikos;L. Carr;Mingzhong Wu
中科院分区：
文献类型：
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作者：
D. Richardson;B. Kalinikos;L. Carr;Mingzhong Wu
首次观察到了依赖于强色散和非线性的非线性波的精确分形，这种波是在磁介质中自发产生的。实验利用微波在准一维磁振子晶体中激发自旋波。当输入微波功率（Pin）较低时，输出信号的功率频谱为单峰。当P_{in}增大到一定程度时，由于调制不稳定性产生新的边模，导致梳状频谱。随着P_{in}的进一步增加，频率梳中的每个峰都可以通过调制不稳定性演化成自己的更细的梳。随着P_{in}进一步增加，可以观察到另一组更精细的频率梳。这种频域分形表现为时域信号中的多层幅度调制。
Exact fractals of nonlinear waves that rely on strong dispersion and nonlinearity and arise spontaneously out of magnetic media were observed for the first time. The experiments make use of a microwave to excite a spin wave in a quasi-one-dimensional magnonic crystal. When the power of the input microwave (P_{in}) is low, the output signal has a power-frequency spectrum that consists of a single peak. When P_{in} is increased to a certain level, new side modes are generated through modulational instability, resulting in a comblike frequency spectrum. With a further increase in P_{in}, each peak in the frequency comb can evolve into its own finer comb through the modulational instability. As P_{in} is increased further, one can observe yet another set of finer frequency combs. Such a frequency-domain fractal manifests itself as multiple layers of amplitude modulation in the time-domain signal.