Linear and second order responses in topological semimetals

DIPC Seminars

Speaker: Yan Sun, Max Planck Institute for Chemical Physics of Solids
When: 2019/05/29
17:00
Place: Donostia International Physics Center
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Linear and second order responses in topological semimetals

We have found that the strong spin Hall effect in TaAs is mainly dominated from the Weyl points and nodal-line-like Fermi surface, which implies a strong interplay between the topological band structure and Berry curvature in topological semimetals. With this guiding principle, we have successfully understood the strong spin Hall effect in IrO2 and found the nodal line band structures in it. This principle was further verified by our developed database. Generalizing this principle to time reversal symmetry broken system, we have proposed strong anomalous Hall effect in magnetic Weyl semimetal Co3Sn2S2. Owing to the low charge carrier density and large Berry curvature from the nodal line band structure, the anomalous Hall conductivity and anomalous Hall angle experimentally reach up to 1130 S/cm and 20%, respectively. Further, the anomalous Hall effect can even exist with zero net moment in the absence of the symmetry operation that changes the sign of Berry curvature, and the anomalous Hall effect can be strongly enhanced by the special band structures of Weyl points and nodal lines. Following this guiding direction, we have predicted a strong anomalous Hall effect in the compensated ferrimagnetic Weyl semimetal Ti2MnAl and noncollinear antiferromagnetic Weyl metal Mn3Ge with vanishing net magnetic moments. Owing to time reversal symmetry, anomalous Hall effect is forbidden in the first order perturbation, but the higher order response can exist. We have studied the Berry curvature dipole induced non-linear anomalous Hall effect, which was experimentally observed very recently.