Creating Weyl Nodes and Tuning Their Energy by Magnetization Rotation in a Metallic Ferromagnet*

Weyl nodes are robust topological features of the electronic structure that can occur at any momentum and energies. To observe the large anomalous effects Weyl nodes need to be close to or at the Fermi-level. However, most materials Weyl nodes are observed slightly away from the Fermi-level.
Here we propose a novel strategy to tune the Weyl node energy close to or even precisely at the Fermi energy that relies on the interplay between the magnetism and the energy dispersion in the time-reversal symmetry breaking Weyl semimetals.
We show that magnetization effect is strong enough to create new Weyl nodes close to the Fermi surface and, vice versa annihilate other Weyl pairs.
We focus on Co3Sn2S2, a ferromagnet recently found to be a Weyl semimetal and to display a large anomalous Hall effect. Performing ab initio density-functional calculations we show that canting the magnetization away from the easy axis leads to large displacements of the Weyl points in energy and in momentum space such that, at different orientations, Weyl fermions can be placed exactly at the Fermi surface.