Unconventional Anomalous Hall Effect in a New Noncollinear Ferromagnetic Weyl Semimetal CeAlSi with Tunable Fermi Level*

Ferromagnetic Weyl semimetals (FM WSMs) have drawn significant attention since they feature an interesting combination of magnetism and band topology. As a result, FM WSMs can host unique electromagnetic responses by bringing the Fermi level close to the Weyl nodes. Here, based on transport and quantum oscillation experiments aided by first-principles calculations, we show that CeAlSi is a new noncollinear FM WSM in which the Fermi level can be tuned to lie as close as 1 meV to the Weyl nodes [1]. Importantly, we observe an unconventional anomalous Hall effect (AHE) that appears (disappears) as the Fermi level lies close to (away from) the Weyl nodes. The close link between the novel AHE and the proximity of Weyl nodes to the Fermi level establishes a new transport response that is induced by the Weyl nodes in CeAlSi. We will discuss the role of topological surface states living on the ferromagnetic domain walls in generating the unusual electromagnetic response in CeAlSi.

[1] H.-Y. Yang et al., arXiv: 2006.07943v2.