High-temperature ideal Weyl semimetal phase and Chern insulator phase in ferromagnetic BaEuNiOsO6 and its (111) (BaEuNiOsO6)/(BaTiO3)10 superlattice

Weyl semimetals (WSMs) have recently stimulated intensive interest because they exhibit fascinating physical properties and also promise exciting technological applications. So far, however, the few confirmed magnetic WSMs generally a large number of points either located away from Fermi level $({E}_{F})$ or shrouded by nontopological surface pockets. Based on first-principles density functional theory calculations, we establish cubic double perovskite ${\mathrm{BaEuNiOsO}}_{6}$ to be high Curie temperature $({T}_{c})$ ferromagnetic (FM) WSM with magnetization along [111] direction, just two pairs at ${E}_{F}$ ${T}_{c}=325$ K. The strong FM is attributed Ni $3d$-Eu $4f$-Os $5d$ coupling induced substitution half Ba atoms Eu in ${\mathrm{Ba}}_{2}{\mathrm{NiOsO}}_{6}$. Moreover, momentum separation one point pair large, thus giving rise not only long (001) arc but anomalous Hall conductivity. Intriguingly, as unique result bulk being WSM, (111) monolayer (ML) superlattice $({\mathrm{BaEuNiOsO}}_{6})/{({\mathrm{BaTiO}}_{3})}_{10}$ found high-temperature (${T}_{c}=210$ K) Chern insulator band gap $\ensuremath{\sim}90$ meV. Therefore, will provide superior material platform for exploring fundamental physics fermions, its ML superlattices offer topological studying exotic quantum phenomena such effect.