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arXiv 2203.02567cond-mat.str-elcond-mat.mtrl-sci
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层状蜂窝铁磁体CrI $_3$中的交换作用和自旋动力学

Exchange interactions and spin dynamics in the layered honeycomb ferromagnet CrI$_3$

Subhadeep Bandyopadhyay, Finn Lasse Buessen, Ritwik Das, Franz G. Utermohlen, Nandini Trivedi, Arun Paramekanti, Indra Dasgupta

摘要:

我们推导了菱形CrI $_3$的微观自旋哈密顿量,采用广泛的第一性原理密度泛函理论(DFT)计算,其中包括自旋轨道耦合和Hubbard U。我们的计算表明,占主导地位的最近邻铁磁海森堡交换较弱的进一步邻居海森堡条款。此外,我们还发现了一个Dzyaloshinskiii-Moriya相互作用,它主要驱动狄拉克点处自旋波谱中的拓扑间隙,并揭示了S=3/2 Cr矩之间不可忽略的反铁磁Kitaev耦合。面外磁矩由弱对称键依赖项和局部单离子各向异性稳定。使用线性自旋波理论,我们发现我们的交换参数是在合理的非弹性中子散射(INS)实验吻合。采用经典的蒙特卡罗模拟,我们研究了磁相变温度$T_c$和它的演变与施加面内磁场。我们进一步演示了如何未来的高分辨率INS实验的磁振子分散的单晶在平面内的磁场可用于定量提取的反铁磁Kitaev交换耦合的强度。

英文摘要:

We derive the microscopic spin Hamiltonian for rhombohedral CrI$_3$ using extensive first-principles density functional theory (DFT) calculations which incorporate spin-orbit coupling and Hubbard U. Our calculations indicate a dominant nearest-neighbor ferromagnetic Heisenberg exchange with weaker further-neighbor Heisenberg terms. In addition, we find a Dzyaloshinskii-Moriya interaction which primarily drives a topological gap in the spin-wave spectrum at the Dirac point, and uncover a non-negligible antiferromagnetic Kitaev coupling between the S=3/2 Cr moments. The out-of-plane magnetic moment is stabilized by weak symmetric bond-dependent terms and a local single-ion anisotropy. Using linear spin wave theory, we find that our exchange parameters are in reasonably good agreement with inelastic neutron scattering (INS) experiments. Employing classical Monte Carlo simulations, we study the magnetic phase transition temperature $T_c$ and its evolution with an applied in-plane magnetic field. We further demonstrate how future high-resolution INS experiments on the magnon dispersion of single crystals in an in-plane magnetic field may be used to quantitatively extract the strength of the antiferromagnetic Kitaev exchange coupling.

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