Emergent topological states via digital (001) oxide superlattices

Abstract

Oxide heterostructures exhibit many intriguing properties. Here we provide design principles for inducing multiple topological states in (001) ($AM$O${}_3$)${}_1$/($A{M}^{\prime }$O${}_3$)${}_1$ oxide superlattices. Aided by first-principles calculations and model analysis, we show that a (Sr$M$O3)${}_1$/(Sr$M^{\prime }$O${}_3$)${}_1$ superlattice ($M$ = Nb, Ta and $M^{\prime }$ = Rh, Ir) is a strong topological insulator with $Z_2$ index (1;001). More remarkably, a (SrMoO3)${}_1$/(SrIrO3)${}_1$ superlattice exhibits multiple coexisting topological insulator (TI) and topological Dirac semi-metal (TDS) states. The TDS state has a pair of type-II Dirac points near the Fermi level and symmetry-protected Dirac node lines. The surface TDS Dirac cone is sandwiched by two surface TI Dirac cones in the energy-momentum space. The non-trivial topological properties arise from the band inversion between $d$ orbitals of two dissimilar transition metal atoms and a particular parity property of (001) superlattice geometry. Our work demonstrates how to induce nontrivial topological states in (001) perovskite oxide heterostructures by rational design.

29 pages, 6 figures and 1 table