论文标题
2D蜂窝晶格中的自旋波$ xxz $ -type van der waals antiferromagnet Cops $ _3 $
Spin-waves in 2D honeycomb lattice $XXZ$-type van der Waals antiferromagnet CoPS$_3$
论文作者
论文摘要
使用粉末非弹性中子散射测量了COPS中的磁激发$ _3 $，一种带有旋转$ s = 3/2 $的二维范德华（VDW）抗铁磁铁。观察到明显的分散旋转波，其较大的自旋间隙约为13 meV。使用$ XXZ $ -Type $ J_1-J_2-J_3 $ HEISENBERG HAMILTONIAN和单离子各向异性均采用$ XXZ $ -TYPE拟合了木否光谱，假设蜂窝层之间没有磁性交换。最佳拟合参数显示了铁电磁交换$ j_1 = -2.08 $ meV和$ j_2 = -0.26 $ meV，最接近和第二名的邻居以及与第三名的Easy-aver-avermagnest neark neven of第三名$ MEV的较大的反铁磁性交换$ j_3 = 4.21 $ MEV，具有强大的Easy-Axis ansisis Anisotropy $ k = -2.06 $ k = -2.06 = -2.06 = -MEV仅通过各向异性$ xxz $ type hamiltonian才能实现合适的拟合，其中，平面外部组件的交换交互小于平面上的交换，而平面成分的比例为$α= j_z/j_x/j_x = 0.6 $。此外，在30 meV左右的没有旋转轨道激子的缺失表明CO $^{2+} $ ions in Cops $ _3 $具有$ s = 3/2 $状态，而不是旋转轨道纠缠的$ J_ \ rm {eff} = 1/2 $地面状态。我们的结果直接表明，COPS $ _3 $是$ XXZ $型号的实验实现，其中honeycomb lattice in 2d VDW磁铁。
The magnetic excitations in CoPS$_3$, a two-dimensional van der Waals (vdW) antiferromagnet with spin $S=3/2$ on a honeycomb lattice, has been measured using powder inelastic neutron scattering. Clear dispersive spin waves are observed with a large spin gap of ~13 meV. The magnon spectra were fitted using an $XXZ$-type $J_1-J_2-J_3$ Heisenberg Hamiltonian with a single-ion anisotropy assuming no magnetic exchange between the honeycomb layers. The best-fit parameters show ferromagnetic exchange $J_1=-2.08$ meV and $J_2=-0.26$ meV for the nearest and second-nearest neighbors and a sizeable antiferromagnetic exchange $J_3=4.21$ meV for the third-nearest neighbor with the strong easy-axis anisotropy $K=-2.06$ meV. The suitable fitting could only be achieved by the anisotropic $XXZ$-type Hamiltonian, in which the exchange interaction for the out-of-plane component is smaller than that for the in-plane one by a ratio $α=J_z/J_x=0.6$. Moreover, the absence of spin-orbit exciton around 30 meV indicates that Co$^{2+}$ ions in CoPS$_3$ have a $S=3/2$ state rather than a spin-orbital entangled $J_\rm{eff}=1/2$ ground state. Our result directly shows that CoPS$_3$ is an experimental realization of the $XXZ$ model with a honeycomb lattice in 2D vdW magnets.
