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arXiv · 2006.07339

Spin Excitations and Spin Wave Gap in the Ferromagnetic Weyl Semimetal Co$_3$Sn$_2$S$_2$

Chang Liu·Jianlei Shen·Jiacheng Gao·Changjiang Yi·Di Liu·Tao Xie·Lin Yang·Sergey Danilkin·Guochu Deng·Wenhong Wang·Shiliang Li·Youguo Shi·Hongming Weng·Enke Liu·Huiqian Luo
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Abstract

We report a comprehensive neutron scattering study on the spin excitations in the magnetic Weyl semimetal Co$_3$Sn$_2$S$_2$ with quasi-two-dimensional structure. Both in-plane and out-of-plane dispersions of the spin waves are revealed in the ferromagnetic state, similarly dispersive but damped spin excitations persist into the paramagnetic state. The effective exchange interactions have been estimated by a semi-classical Heisenberg model to consistently reproduce the experimental $T_C$ and spin stiffness. However, a full spin wave gap below $E_g=2.3$ meV is observed at $T=4$ K, much larger than the estimated magnetic anisotropy energy ($\sim0.6$ meV), while its temperature dependence indicates a significant contribution from the Weyl fermions. These results suggest that Co$_3$Sn$_2$S$_2$ is a three-dimensional correlated system with large spin stiffness, and the low-energy spin dynamics could interplay with the topological electron states.

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Chang Liu, Jianlei Shen, Jiacheng Gao, Changjiang Yi, Di Liu, Tao Xie, Lin Yang, Sergey Danilkin, Guochu Deng, Wenhong Wang, Shiliang Li, Youguo Shi, Hongming Weng, Enke Liu, Huiqian Luo. 2020-06-12. Spin Excitations and Spin Wave Gap in the Ferromagnetic Weyl Semimetal Co$_3$Sn$_2$S$_2$. https://doi.org/10.1007/s11433-020-1597-6

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