Theory for Magnetic Anisotropy of Field-Induced Insulator-to-Metal Transition in Cubic Kondo Insulator YbB12

摘要: Magnetization and energy gap of Kondo insulator YbB_{12} are calculated theoretically based on the previously proposed tight-binding model composed Yb 5d$\epsilon$ 4f $\Gamma_8$ orbitals. It is found that magnetization curves almost isotropic, naturally expected from cubic symmetry, but gap-closing field has an anisotropy: closes faster for in (100) direction than (110) (111) directions, accord with experiments. This qualitatively understood by considering maximal eigenvalues total angular momentum operators projected each magnetic field. But numerical calculation band yields better agreement experiment.