Exotic Magnetotransport in Simple Magnetic Weyl Semimetal Films

Magnetic Weyl semimetals host singularities called Weyl points in their band structures, and exotic magnetotransport phenomena involving the Weyl points have been intensively studied. Magnetic Weyl semimetals discovered so far may be classified into two major groups. The first group includes Mn₃Sn, Co₃Sn₂S₂, and Co₂MnGa, which have 3d transition metal elements as magnetic elements and are characterized by high magnetic transition temperatures. On the other hand, these materials have high carrier density and complex band structures hosting Weyl points. The second group includes EuCd₂Sb₂ and GdPtBi, which have 4f rare earth elements as magnetic elements. Their magnetic transition temperatures are low, and it is necessary to apply a magnetic field for inducing the ferromagnetic Weyl phase. In these materials, their carrier density is low, and Weyl points occupy a large area compared to the Fermi surface. It is thus expected that exotic magnetotransport can be controlled and enhanced using thin-film techniques.
Based on our knowledge about film growth of II-V compounds such as Cd₃As₂ [1,2] and its combination to Eu magnetic elements [3-5], we have succeeded for the first time in fabricating single-crystalline EuCd₂Sb₂ thin films by molecular beam epitaxy [6]. While these films exhibit the same antiferromagnetic and field-induced ferromagnetic phases as EuCd₂Sb₂ bulks, they show a very large anomalous Hall effect compared to the bulks. We have systematically controlled the carrier density with electrostatic gating and have found that the anomalous Hall effect exhibits a sharp peak structure as function of carrier density. As also demonstrated by first-principles calculation, the intrinsic anomalous Hall conductivity is maximized reflecting the presence of Weyl points.
I will also present results about EuCd₂As₂, another Weyl semimetal candidate, and extensively discuss exotic magnetotransport phenomena appearing in simple magnetic Weyl semimetal films.

References
[1] Y. Nakazawa et al., APL Mater. 7, 071109 (2019)
[2] Y. Nakazawa et al., Phys. Rev. B 103, 045109 (2021)
[3] M. Ohno et al., APL Mater. 9, 051107 (2021)
[4] M. Uchida et al., Sci. Adv. 7, eabl5381 (2021)
[5] M. Ohno et al., Phys. Rev. B 103, 165144 (2021)
[6] M. Ohno et al., Phys. Rev. B 105, L201101 (2022)