Theory of spin-orbit coupling at LaAlO3/SrTiO3 interfaces and SrTiO3 surfaces

A full theoretical understanding of the spin-orbit coupling (SOC) effects at LaAlO$_{3}$/SrTiO$_{3}$ interfaces and SrTiO$_{3}$ surfaces is still needed. We perform first-principles density-functional-theory calculations and derive from these a simple tight-binding Hamiltonian, through a Wannier function projection and group theoretical analysis. We find striking differences to the standard Rashba theory for spin-orbit coupling in semiconductor heterostructures, because the relevant $t_{2g}$ orbitals are very different from nearly free electrons. The key ingredients to the spin splitting are the atomic SOC and the interface asymmetry, which enters via asymmetric $t_{2g}$ orbital lobes. ArXiv:1209.4705 by Zhicheng Zhong, Anna Toth, Karsten Held