Half-Metallic Semi-Dirac-Point Generated by Quantum Confinement in TiO2/VO2 Nanostructures

Multilayer VO2/TiO2 nanostructures (d(1)-d(0) interfaces with no polar discontinuity) are studied with first-principles density functional methods including structural relaxation. Quantum confinement of the half-metallic VO2 slab within insulating TiO2 produces an unexpected and unprecedented two-dimensional new state, with a (semi-Dirac) point Fermi surface: spinless charge carriers are effective-mass-like along one principal axis but are massless along the other. Effects of interface imperfection are addressed.