Thickness-dependent quantum transport of Weyl fermions in ultrahigh-quality SrRuO₃ films

Emergence of the magnetic Weyl semimetal state has recently been reported in ultrahigh-quality SrRuO₃ thin films [1,2], providing a new platform for exploring novel physics related to a pair of Weyl nodes in epitaxial heterostructures. However, there is a dearth of knowledge on the thickness dependence of the quantum transport properties peculiar to the magnetic Weyl semimetal state in it, and hence, we investigated magnetotransport properties of SrRuO₃ with various thicknesses (t = 1–60 nm). Signatures of Weyl fermions—unsaturated linear positive magnetoresistance accompanied with a quantum oscillation having a non-trivial Berry phase—were observed for t ≥ 10 nm. The residual resistivity increases with decreasing film thickness, indicating more disorder near the interface. This thickness-dependent scattering affects magnetic properties as well. The Curie temperature decreases and the coercive field increases with decreasing thickness. These results provide a guideline for designing SrRuO₃-based functional heterostructures in which Weyl fermions play an essential role.
[1] K. Takiguchi, Y. K. Wakabayashi et al., Nat. Commun. 11, 4969 (2020).
[2] Y. K. Wakabayashi et al., APL Mater. 7, 101114 (2019).