Weyl nodal-line surface half-metal in CaFeO3

Manipulating the spin degrees of freedom of electrons affords an excellent platform for exploring novel quantum states in condensed-matter physics and material science. Based on first-principles calculations and analysis of crystal symmetries, we propose a fully spin-polarized composite semimetal state, which is combined with the 1D nodal lines and 2D nodal surfaces, in the half-metal material CaFeO3. In the nodal line-surface half-metal, the Baguenaudier-like nodal lines feature six rings linked together, which are protected by the three independent symmetry operations: PT, My, and Mz. Near the Fermi level, 2D nodal surfaces with fully spin-polarized are guaranteed by the joint operation TS2i in the ki(i=x,y,z)=π plane. Furthermore, high-quality CaFeO3 harbors ultraclean energy dispersion, which is rather robust against strong hydrostatic compressional strain and correlation effect. The realization of the Weyl nodal line-surface half-metal presents great potential for spintronics applications with high-speed and low-power consumption.