Dark discrete breather modes in a monoaxial chiral helimagnet with easy-plane anisotropy
Dark discrete breather modes in a monoaxial chiral helimagnet with easy-plane anisotropy
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DOI：
10.1103/physrevb.104.214420
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发表时间：
2021-12
影响因子：
3.7
通讯作者：
I. G. Bostrem;E. Ekomasov;J. Kishine;A. Ovchinnikov;V. Sinitsyn
中科院分区：
文献类型：
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作者：
I. G. Bostrem;E. Ekomasov;J. Kishine;A. Ovchinnikov;V. Sinitsyn
非线性和离散性是各种介质中出现离散呼吸子激励的两个关键因素。我们认为，这些要求得到满足，在强制铁磁相的单轴手性helimagnet CrNb$_3$S$_6$由于特定的域结构的化合物。固定的，时间周期的呼吸模式出现的离散呼吸晶格解决方案，其周期与系统的大小不匹配。由于CrNb$_3$S$_6$固有的易平面单离子各向异性，这些模式是暗型的，其频率位于线性自旋波带内，靠近其底部边缘。它们代表椭圆余弦磁化状态，类似于众所周知的孤子晶格基态，具有不同但数量有限的嵌入式$2\pi$-扭结。这些黑暗的呼吸模式的线性稳定性进行了验证，通过Floquet分析。它们的能量受呼吸晶格周期和振幅两个参数控制，福尔斯随扭结数的增加而线性下降。这些结果为基于手征螺旋磁网络的自旋电子谐振器的设计开辟了一条新的途径。
Nonlinearity and discreteness are two pivotal factors for an emergence of discrete breather excitations in various media. We argue that these requirements are met in the forced ferromagnetic phase of the monoaxial chiral helimagnet CrNb$_3$S$_6$ due to specific domain structure of the compound. The stationary, time-periodic breather modes appear as the discrete breather lattice solutions whose period mismatches with a system size. Thanks to easy-plane single-ion anisotropy intrinsic to CrNb$_3$S$_6$, these modes are of the dark type with frequencies lying within the linear spin-wave band, close to its bottom edge. They represent cnoidal states of magnetization, similar to the well-known soliton lattice ground state, with differing but limited number of embedded $2\pi$-kinks. Linear stability of these dark breather modes is verified by means of the Floquet analysis. Their energy controlled by two parameters, namely the breather lattice period and amplitude, falls off linearly with a growth of the kink number. These results may pave a new path to design spintronic resonators on the base of chiral helimagnets.