Chern and Z2 topological insulating phases in perovskite-derived 4d and 5d oxide buckled honeycomb lattices

Abstract

Based on density functional theory calculations including a Coulomb repulsion parameter U, we explore the topological properties of (LaXO3)2/(LaAlO3)4 (111) with X = 4d and 5d cations. The metastable ferromagnetic phases of LaTcO3 and LaPtO3 with preserved P321 symmetry emerge as Chern insulators (CI) with C = 2 and 1 and band gaps of 41 and 38 meV at the lateral lattice constant of LaAlO3, respectively. Berry curvatures, spin textures as well as edge states provide additional insight into the nature of the CI states. While for X = Tc the CI phase is further stabilized under tensile strain, for X = Pd and Pt a site disproportionation takes place when increasing the lateral lattice constant from aLAO to aLNO. The CI phase of X = Pt shows a strong dependence on the Hubbard U parameter with sign reversal for higher values associated with the change of band gap opening mechanism. Parallels to the previously studied (X2O3)1/(Al2O3)5 (0001) honeycomb corundum layers are discussed. Additionally, non-magnetic systems with X = Mo and W are identified as potential candidates for Z2 topological insulators at aLAO with band gaps of 26 and 60 meV, respectively. The computed edge states and Z2 invariants underpin the non-trivial topological properties.

High Chern numbers in a perovskite-derived dice lattice (LaXO3)3/(LaAlO3)3(111) with X = Ti, Mn and Co

“…Model Hamiltonian studies in conjunction with DFT calculations predicted a distinct set of four bands in (111) bilayers of LaNiO , two nearly flat interconnected by two dispersive ones with a Dirac crossing at and a quadratic band touching at 8 – 11 . Systematic DFT+ U calculations have shown that this set of bands occurs also for La X O ( Mn and Co 12 ) and a Chern insulator phase driven by spin-orbit coupling (SOC) can emerge in (111) bilayers of La X O ( Mn 12 , 13 , Co 12 , Ru, Os 14 , Pd, and Pt 15 , 16 ). The (111)-oriented LaMnO buckled honeycomb bilayer was predicted to have a nontrivial band gap of 150 meV and a quantized anomalous Hall conductivity of 12 .…”

Chern insulating phases and thermoelectric properties of EuO/MgO(001) superlattices

“…Further candidates for quantum anomalous Hall insulators (QAHI) are LaRuO 3 and LaOsO 3 24 , as well as the metastable symmetric ferromagnetic cases of LaPdO 3 , LaPtO 3 and LaTcO 3 25,26 honeycomb bilayers encased in LaAlO 3 (111). Corundum-derived SL provide another realization of the honeycomb lattice.…”