Insights from magnetic Weyl semimetals: the Berry phase and beyond*

It is known that Bloch electrons pick up an anomalous velocity because of the Berry curvature in the magnetic material. Recent discovery of magnetic Weyl semimetals (WSMs) provides a novel, ideal platform to examine the Berry curvature-induced transport phenomena, such as the anomalous Hall effect (AHE) and the thermal version of AHE. We focus on the Wideman-Franz law that governs the fundamental correlation between the charge and heat transport. We reveal a novel mechanism [1] to violate the Wideman-Franz law at the finite temperature by the Berry curvature distribution rather than the inelastic scattering effect, which is distinct from the ordinary (longitudinal) transport. Beyond the linear-response phenomena like AHE, WSMs can generate giant nonlinear optical response (such as the DC photocurrent), which is commonly attributed to the Berry curvature too. As a WSM turns magnetic, however, we find a new class of photocurrent [2,3] by re-examining the nonlinear response theory. It is contributed by the diabatic effect, instead of the Berry phase. Because this is a leading-order phenomena, the induced photocurrent is expected to be much larger compared to the non-magnetic case.
[1] L. Xu et al. arXiv:1812.04339 (2018) [2] Y. Zhang et al. Nature Commun. 10, 3783 (2019). [3] T. Holder et al. in preparation.