Anisotropic magnetoresistance and magnetic field-tunable Weyl nodes in Weyl metal SrRuO₃ thin films

Weyl semimetals are a unique class of topological materials, possessing Fermi-arc surface states and exhibiting the chiral anomaly effect. The chiral anomaly effect refers to a non-equilibrium charge transfer within a Weyl-node pair of opposite chirality under the condition of aligned electric and magnetic fields, leading to non-conserved chiral charges and thus enhanced electrical conductivity. In experiments, such an enhanced conductivity due to the chiral anomaly manifests as a negative longitudinal magnetoresistance (MR) when the external field H is applied along the bias current direction I. In this work, we present rigorous φ- and α-dependent magnetotransport measurements to investigate such a negative longitudinal MR due to chiral anomaly in a sunbeam-shaped device fabricated from an untwinned Weyl metal SrRuO₃ (SRO) thin film. Here, φ(α) represents the angle between I and the in-plane H(SRO monoclinic [001]_o). Unusual φ dependences of in-plane MR and Hall effects were uncovered at low temperatures, accompanied by the emergence of the fourfold symmetric component in the in-plane MR. These results indicate that the chiral anomaly effect and resistivity anisotropy in SRO play important roles. In particular, the dramatic variation of Weyl nodes near the Fermi level through magnetic field manipulation of the magnetization orientation, as revealed by band structure calculations, is consistent with the observed in-plane MR and Hall effect.