Ferromagnetic Weyl semimetals and their electromagnetic response in RAlX materials class (R= Ce or Pr and X = Si or Ge)

Ferromagnetic Weyl semimetals (FMWSMs) are exotic topological materials in which nontrivial band topology and magnetism drive novel electromagnetic responses such as the anomalous Hall effect (AHE). Currently available FMWSMs are limited to materials that preserve the inversion symmetry and generate the Weyl nodes by breaking the time-reversal symmetry (TRS). Here we present RAlX materials (R= Ce, Pr; X = Si, Ge) as new FMWSMs where the Weyl nodes are stabilized by breaking the inversion symmetry and their separation is controlled by breaking TRS. They show an unconventional AHE that can be tuned continuously by controlling the dispersion of the Weyl nodes. Based on our systematic first-principles calculations and transport measurements, we show that PrAlGe_1-xSi_x (x = 0-1) is a type II FMWSM with an AHE that shows a transition from an intrinsic mechanism driven by the Berry curvature to an extrinsic scattering mechanism [1]. In contrast, CeAlSi is a noncollinear FMWSM with type I Weyl nodes [2]. It shows an AHE that appears (disappear) as the Fermi level is tuned to lie close to (away from) the Weyl nodes. Our study uncovers RAlX as a new, tunable FMWSM family hosting unconventional AHE.

1. H.-Y. Yang et al., APL Mater. 8, 011111 (2020).
2. H.-Y. Yang et al., arXiv: 2006.07943v2.