Fermi‐Surface Modeling of Light‐Rare‐Earth Hexaborides with 2D‐ACAR Spectroscopy

Two dimensional angular correlation of the positron annihilation radiation (2D-ACAR) spectra are measured for $\mathrm{LaB}_6$ along high symmetry directions and compared with first principle calculations based on density functional theory (DFT). This allows modeling Fermi surface in terms ellipsoid electron pockets centered at $X$-points elongated $\Sigma$ axis (${\Gamma-M}$ direction). The obtained structure is agreement quantum oscillation measurements previous band calculations. For isostructural topologically not-trivial $\mathrm{SmB}_6$ similar ellipsoids connected through necks that have significantly smaller radii case $\mathrm{LaB}_6$. A theoretical analysis 2D-ACAR also performed $\mathrm{CeB}_6$ including on-site repulsion $U$ correction to local-density approximation (LDA+$U$) DFT. similarities Fermi-surface projections these two compounds allow infer both trivial correlated metals.