Spin Excitations and Spin Wave Gap in the Ferromagnetic Weyl Semimetal Co3Sn2S2
Abstract
We report a comprehensive neutron scattering study on the spin excitations in the magnetic Weyl semimetal Co3Sn2S2 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 TC and spin stiffness. However, a full spin wave gap below Eg=2.3 meV is observed at T=4 K, much larger than the estimated magnetic anisotropy energy (0.6 meV), while its temperature dependence indicates a significant contribution from the Weyl fermions. These results suggest that Co3Sn2S2 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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