Decoupling electron correlation and band topology in a Hund's metal via (111) strain engineering

Conventional (001) compressive strain typically exacerbates octahedral buckling, driving Hund's metals like SrRuO3 into strongly correlated regimes. Here, we circumvent this via (111)-oriented SrRuO3 epitaxial films. Unlike conventional Poisson expansion, the compressed (111) lattice clamps the out-of-plane parameter and suppresses the intrinsic c+ octahedral rotation. The anomalous unbuckling straightens Ru-O-Ru bonds and dilutes effective Hund–Hubbard correlations. O K-edge x-ray absorption spectroscopy confirms this dilution, revealing a direct spectral weight transfer from incoherent multiplet states to the coherent quasiparticle pole. Macroscopically, the Fermi liquid coherence temperature is enhanced to 40 K under −1.8% strain. Furthermore, magnetotransport is consistent with the preservation of the intrinsic momentum-space Berry curvature and ferromagnetic ground state. Ultimately, this (111) geometric unbuckling provides a quantitative pathway to decouple electron correlation and band topology in complex oxides.