Role of on-site Coulomb interactions in the half-metallic Weyl ferromagnet candidate thin-film CoFeSi

Sumida, Kazuki   ; Fujita, Yuichi*; Zhou, W.*; Masuda, Keisuke*; Kawasaki, Ikuto  ; Fujimori, Shinichi   ; Kimura, Akio*; Sakuraba, Yuya*

We investigated the element-specific electronic structure of a half-metallic Weyl ferromagnet candidate CoFeSi film by utilizing soft-X-ray resonant photoelectron spectroscopy and first-principles calculations with/without considering on-site Coulomb interaction. Fe 2-3 resonant photoelectron experiment revealed that the Fe 3 states exist around 2 and 4 eV below the Fermi energy. Our calculations, based on the generalized gradient approximation without considering Coulomb interaction at the Fe site, successfully reproduced the experimentally observed Fe 3 partial density of states. Our findings shed light on the highly controversial correlation effect of CoFeSi, offering valuable insights into its half-metallicity and Weyl semi-metallicity.