Abstract
Mn3Sn has recently attracted considerable attention as a magnetic Weyl semimetal exhibiting concomitant transport anomalies at room temperature. The topology of the electronic bands, their relation to the magnetic ground state and their nonzero Berry curvature lie at the heart of the problem. The examination of the full magnetic Hamiltonian reveals otherwise hidden aspects of these unusual physical properties. Here, we report the full spin wave spectra of Mn3Sn measured over a wide momentum—energy range by the inelastic neutron scattering technique. Using a linear spin wave theory, we determine a suitable magnetic Hamiltonian which not only explains the experimental results but also stabilizes the low-temperature helical phase, consistent with our DFT calculations. The effect of this helical ordering on topological band structures is further examined using a tight binding method, which confirms the elimination of Weyl points in the helical phase. Our work provides a rare example of the intimate coupling between the electronic and spin degrees of freedom for a magnetic Weyl semimetal system.
Highlights
It is an intriguing question of how certain electronic band structures give rise to nontrivial topological properties
Because our inelastic neutron scattering experiment was done at 5 K, extra effects from the low-temperature phase must be considered rather than just using the room temperature phase
We can safely ignore the contribution by τ1 for our spin waves calculations, since the diffraction peak of τ1 is much weaker than the other one.[26]
Summary
It is an intriguing question of how certain electronic band structures give rise to nontrivial topological properties. Systems with Weyl points exhibit a nontrivial Berry’s phase, which can be characterized by measuring transport anomalies such as the anomalous Hall effect. Mn3Sn, a non-collinear metallic antiferromagnet whose magnetic ions sit on a kagome lattice, has recently drawn growing interest for its rather remarkable transport anomalies. Density functional calculations examining the Weyl points[2,3] and transport measurements[4,5,6,7,8] of Mn3Sn show that this antiferromagnetic metal exhibits significant transport anomalies at room temperature. It was suggested that it may have spin polarized current, which would make it an interesting candidate for spintronics applications.[10]
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