Nonlinear Magnon Polaritons

We experimentally and theoretically demonstrate that nonlinear spin-wave interactions suppress the hybrid magnon-photon quasiparticle or "magnon polariton" in microwave spectra of a yttrium iron garnet film detected by an on-chip split-ring resonator. We observe a strong coupling between the Kittel and microwave cavity modes in terms of an avoided crossing as a function of magnetic fields at low microwave input powers, but a complete closing of the gap at high powers. The experimental results are well explained by a theoretical model including the three-magnon decay of the Kittel magnon into spin waves. The gap closure originates from the saturation of the ferromagnetic resonance above the Suhl instability threshold by a coherent backreaction from the spin waves.

我们通过实验和理论证明，非线性自旋波相互作用抑制了由片上开口环谐振器检测的钇铁石榴石薄膜微波光谱中的混合磁振子 - 光子准粒子或“磁振子极化激元”。我们在低微波输入功率下，根据作为磁场函数的避免交叉观察到基特尔模式和微波腔模式之间的强耦合，但在高功率下能隙完全闭合。包含基特尔磁振子到自旋波的三磁振子衰变的理论模型很好地解释了实验结果。能隙闭合源于自旋波的相干反作用使苏尔不稳定性阈值以上的铁磁共振达到饱和。