Ab initio study of Z_2 topological phases in perovskite (111) (SrTiO_3)_7/(SrIrO_3)_2 and (KTaO_3)_7/(KPtO_3)_2 multilayers

摘要

Honeycomb structures formed by the growth of perovskite 5d transition metal oxide heterostructures along the (111) direction in a t_(2g)~5 configuration can give rise to topological ground states characterized by a topological index v = 1, as reported by Xiao et al. [Nat. Commun. 2, 596 (2011)]. Using a combination of a tight binding model and ab initio calculations we study the multilayers (SrTiO_3)_7/(SrIrO_3)_2 and (KTaO_3)_7/(KPtO_3)_2 as a function of parity asymmetry, on-site interaction U, and uniaxial strain and determine the nature and evolution of the gap. According to our density functional theory calculations, (SrTiO_3)_7/(SrIrO_3)_2 is found to be a topological semimetal whereas (KTaO_3)_7/(KPtO_3)_2 is found to present a topological insulating phase that can be understood as the high U limit of the previous one, that can be driven to a trivial insulating phase by a perpendicular external electric field.