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.