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The dice lattice, containing a stack of three triangular lattices, has been proposed to exhibit nontrivial flat bands with nonzero Chern numbers, but unlike the honeycomb lattice it is much less studied. By employing density-functional theory (DFT) calculations with an on-site Coulomb repulsion term, we explore systematically the electronic and topological properties of (LaXO 3 ) 3 /(LaAlO 3 ) 3 (111) superlattices with X = Ti, Mn and Co, where a LaAlO 3 trilayer spacer confines the LaXO 3 (LXO) dice lattice. In the absence of spin-orbit coupling (SOC) with symmetry constrained to P3, the ferromagnetic (FM) phase of the LXO(111) trilayers exhibits a half-metallic band structure with multiple Dirac crossings and coupled electron-hole pockets around the Fermi energy. Symmetry lowering induces a significant rearrangement of bands and triggers a metal-to-insulator transition. Inclusion of SOC leads to a substantial anomalous Hall conductivity (AHC) around the Fermi energy reaching values up to [Formula: see text] for X = Mn and Co in P3 symmetry and both in- and out-of-plane magnetization directions in the first case and along [001] in the latter. The dice lattice emerges as a promising playground to realise nontrivial topological phases with high Chern numbers., (© 2023. The Author(s).)

Based on density functional theory calculations including a Coulomb repulsion parameter U, we explore the topological properties of (LaXO 3 ) 2 /(LaAlO 3 ) 4 (111) with X = 4d and 5d cations. The metastable ferromagnetic phases of LaTcO 3 and LaPtO 3 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 LaAlO 3 , 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 a LAO to a LNO . 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 (X 2 O 3 ) 1 /(Al 2 O 3 ) 5 (0001) honeycomb corundum layers are discussed. Additionally, non-magnetic systems with X = Mo and W are identified as potential candidates for Z 2 topological insulators at a LAO with band gaps of 26 and 60 meV, respectively. The computed edge states and Z 2 invariants underpin the non-trivial topological properties.

The diverse functionality emerging at oxide interfaces calls for a fundamental understanding of the mechanisms and control parameters of electronic reconstructions. Here, we explore the evolution of electronic phases in (LaAlO3)M/(SrTiO3)N (001) superlattices as a function of strain and confinement of the SrTiO3 quantum well. Density functional theory calculations including a Hubbard U term reveal a charge ordered Ti(3+) and Ti(4+) state for N = 2 with an unanticipated orbital reconstruction, displaying alternating d(xz) and d(yz) character at the Ti(3+) sites, unlike the previously reported d(xy) state, obtained only for reduced c-parameter at a(STO). At aLAO c-compression leads to a Dimer-Mott insulator with alternating d(xz), d(yz) sites and an almost zero band gap. Beyond a critical thickness of N = 3 (a(STO)) and N = 4 (aLAO) an insulator-to-metal transition takes place, where the extra e/2 electron at the interface is redistributed throughout the STO slab with a d(xy) interface orbital occupation and a mixed d(xz) + d(yz) occupation in the inner layers. Chemical variation of the SrTiO3 counterpart (LaAlO3 vs. NdGaO3) proves that the significant octahedral tilts and distortions in the SrTiO3 quantum well are induced primarily by the electrostatic doping at the polar interface and not by variation of the SrTiO3 counterpart.