Stability and electronic structure studies of LaAlO₃/SrTiO₃ (110) heterostructures

The first-principles calculations are employed to investigate the stability, magnetic, and electrical properties of the oxide heterostructure of LaAlO₃/SrTiO₃ (110). By comparing their interface energies, it is obtained that the buckled interface is more stable than the abrupt interface. This result is consistent with experimental observation. At the interface of LaAlO₃/SrTiO₃ (110) heterostructure, the Ti-O octahedron distortions cause the Ti t_{m 2g} orbitals to split into the two-fold degenerate d_xz/d_yz and nondegenerate d_xy orbitals. The former has higher energy than the latter. The partly filled two-fold degenerate t_2g orbitals are the origin of two-dimensional electron gas, which is confined at the interface. Lattice mismatch between LaAlO₃ and SrTiO₃ leads to ferroelectric-like lattice distortions at the interface, and this is the origin of spin-splitting of Ti 3d electrons. Hence the magnetism appears at the interface of LaAlO₃/SrTiO₃ (110).