We demonstrate the quantum transport evidence of the Weyl fermions in an epitaxial SrRuO3 film with the best crystalline quality ever reported. We grew 63-nm thick SrRuO3 films by our recently developed machine-learning-assisted molecular beam epitaxy. The residual resistivity ratio [ρ(300 K)/ρ(T→0 K)] of the film reached the world’s best value of 84, enabling direct observations of quantum transport evidence of Weyl fermions. Our results establish SrRuO3 as a magnetic Weyl semimetal.

K. Takiguchi, Y. K. Wakabayashi* (co-first), et al.
Nature Communications 11, 4969 (2020).