Multiple magnon modes in the Co${}_3$Sn${}_2$S${}_2$ Weyl semimetal candidate

Abstract

We experimentally investigate electron transport in kagome-lattice ferromagnet Co${}_3$Sn${}_2$S${}_2$, which is regarded as a time-reversal symmetry broken Weyl semimetal candidate. We demonstrate $dV/dI(I)$ curves with pronounced asymmetric $dV/dI$ spikes, similar to those attributed to current-induced spin-wave excitations in ferromagnetic multilayers. In contrast to multilayers, we observe several $dV/dI$ spikes' sequences at low, $\approx$10${}^4$ A/cm${}^2$, current densities for a thick single-crystal Co${}_3$Sn${}_2$S${}_2$ flake in the regime of fully spin-polarized bulk. The spikes at low current densities can be attributed to novel magnon branches in magnetic Weyl semimetals, which are predicted due to the coupling between two magnetic moments mediated by Weyl fermions. Presence of spin-transfer effects at low current densities in Co${}_3$Sn${}_2$S${}_2$ makes the material attractive for applications in spintronics.

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