Two-dimensional type-II Dirac fermions in a LaAlO3/LaNiO3/LaAlO3 quantum well

Abstract

The type-II Dirac fermions that are characterized by a tilted Dirac cone and anisotropic magneto-transport properties have been recently proposed theoretically and confirmed experimentally. Here, we predict the emergence of two-dimensional type-II Dirac fermions in LaAlO3/LaNiO3/LaAlO3 quantum-well structures. Using first-principles calculations and model analysis, we show that the Dirac points are formed at the crossing between the dx2-y2 and dz2 bands protected by the mirror symmetry. The energy position of the Dirac points can be tuned to appear at the Fermi energy by changing the quantum-well width. For the quantum-well structure with a two-unit cell thick LaNiO3 layer, we predict the coexistence of the type-II Dirac points and the Dirac nodal line. The results are analyzed and interpreted using a tight-binding model and symmetry arguments. Our findings offer a practical way to realize the 2D type-II Dirac fermions in oxide heterostructures.