Multiple magnon modes in a magnetic Weyl semimetal (Vol. 51, No. 1)

dV/dI spikes’ positions, which demonstrate several magnon branches with the linear field dependence.

An area of interest in condensed matter physics is topological Weyl semimetals (WSMs). There are only a few candidates of magnetically ordered materials for the realisation of WSMs, like the kagome-lattice ferromagnet Co3Sn2S2.

Novel magnon branches are predicted in magnetic Weyl semimetals, which can be understood as a result of the coupling between two magnetic moments mediated by Weyl fermions. Here, we experimentally investigate electron transport in the kagome-lattice ferromagnet Co3Sn2S2, which is regarded as a time-reversal symmetry broken Weyl semimetal candidate. We demonstrate dV/I(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, ≈104 A/cm2 , current densities for a thick single-crystal Co3Sn2S2 flake in the regime of fully spin-polarised 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. The presence of spin-transfer effects at low current densities in Co3Sn2S2 makes the material attractive for applications in spintronics.

O. O. Shvetsov et al, Multiple magnon modes in the Co3Sn2S2Weyl semimetal candidate, EPL 127, 57002 (2019)