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arXiv 2205.07367cond-mat.mtrl-sci
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拓扑绝缘体-反铁磁双层结构中的表面等离子体-声子-磁振子极化激元

Surface plasmon-phonon-magnon polariton in a topological insulator-antiferromagnetic bilayer structure

D. Quang To, Zhengtianye Wang, Yongchen Liu, Weipeng Wu, M. Benjamin Jungfleisch, John Q. Xiao, Joshua M. O. Zide, Stephanie Law, Matthew F. Doty

摘要:

我们提出了一个强大的技术计算研究表面极化激元模式的混合材料。我们使用一个半经典的模型,使我们能够理解背后的物理混合系统的集体激发之间的相互作用,并制定了散射和转移矩阵的方法,施加适当的边界条件来解决麦克斯韦方程组,并推导出一个一般方程描述的表面极化激元在异质结构组成的N个组成材料。我们将这种方法应用于由拓扑绝缘体(TI)和反铁磁材料(AFM)组成的测试结构,研究由此产生的表面狄拉克等离子体-声子-磁振子极化激元(DPPMP)。我们发现,两个组分的激发之间的相互作用导致的杂化模式的形成和避免交叉点的出现在DPPMP的色散关系。对于Bi 2Se 3 TI材料的特定情况,当增加TI薄膜的厚度时,具有低于2 THz的低频的极化激元分支发生红移,这导致TI层的厚度上界,其将允许强耦合的可观察的特征和杂化状态的出现。我们还发现,TI和AFM之间的耦合的强度,这是参数化的两个极化激元分支之间的避免交叉分裂的幅度在磁振子共振频率,依赖于磁偶极子的大小和线的宽度的AFM材料,以及在TI的狄拉克等离子体的费米能。最后,我们预测,材料具有极高的质量,即低散射损耗率,是必不可少的,以实现实验观察到的TI和AFM之间的强耦合。

英文摘要:

We present a robust technique for computationally studying surface polariton modes in hybrid materials. We use a semi-classical model that allows us to understand the physics behind the interactions between collective excitations of the hybrid system and develop a scattering and transfer matrix method that imposes the proper boundary conditions to solve Maxwell equations and derive a general equation describing the surface polariton in a heterostructure consisting of N constituent materials. We apply this method to a test structure composed of a topological insulator (TI) and an antiferromagnetic material (AFM) to study the resulting surface Dirac plasmon-phonon-magnon polariton (DPPMP). We find that interactions between the excitations of the two constituents result in the formation of hybridized modes and the emergence of avoided-crossing points in the dispersion relations for the DPPMP. For the specific case of a Bi2Se3 TI material, the polariton branch with low frequency below 2 THz redshifts upon increasing the thickness of TI thin film, which leads to an upper bound on the thickness of the TI layer that will allow an observable signature of strong coupling and the emergence of hybridized states. We also find that the strength of the coupling between the TI and the AFM, which is parameterized by the amplitude of the avoided-crossing splitting between the two polariton branches at the magnon resonance frequency, depends on the magnitude of the magnetic dipole and the line width of the magnon in the AFM material as well as on the Fermi energy of Dirac plasmon in the TI. Finally, we predict that materials with extremely high quality, i.e. low scattering loss rate, are essential to achieve an experimentally-observable strong coupling between a TI and AFM.

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