Electronic reconstruction in (001) and (111) oriented LaAlO3/SrTiO3 interfaces

The observation of a quasi two-dimensional electron gas (q2DEG), superconductivity and magnetism at the (001) interface between the band insulators LaAlO3 (LAO) and SrTiO3 (STO) has opened possibilities for novel electronics applications. Based on density functional calculations, we explore if these multifunctional properties can be extended by changing the crystal orientation from (001) to (111). Despite the difference in stacking with AO and BO2 planes of the perovskite ABO3 structure in (001) oriented superlattices versus AO3 and B layers in the (111) direction, analogous effects such as polar discontinuity arise when the A and B cations are varied across the interface. A further intriguing feature in (111) oriented interfaces is the formation of a buckled honeycomb lattice of the B-site cations. This lattice geometry, well known from graphene, promises to host even more exotic topological phases. The effect of interface termination, thickness of the substrate and strain is discussed.