Lattice relaxation, electronic screening, and spin and orbital phase diagram of LaTiO$_3$/SrTiO$_3$ superlattices

Using first-principles density functional theory calculations, we examined the ground state property of LaTiO$_3$/LaAlO$_3$ superlattice. Total energy calculations, taking account of the structural distortions, $U$ dependence, and exchange correlation functional dependence, show that the spin and orbital ground state can be controlled systematically by the epitaxial strain. In the wide range of strains, ferromagnetic spin and antiferro orbital ordering are stabilized, which i...

We have investigated the structural phase transitions of the transition metal oxide perovskites SrTiO$_{3}$, LaAlO$_{3}$ and LaTiO$_{3}$ using the screened hybrid density functional of Heyd, Scuseria and Ernzerhof (HSE06). We show that HSE06-computed lattice parameters, octahedral tilts and rotations, as well as electronic properties, are significantly improved over semilocal functionals. We predict the crystal field splitting ($\Delta_{CF}$) resulting from the structural pha...

The density functional plus U method is used to obtain the electronic structure, lattice relaxation and metal-insulator phase diagram of superlattices consisting of $m$ layers of Gadolinium Titanate (GdTiO$_{3}$) alternating with $n$ layers of Strontium Titanate (SrTiO$_{3}$). Metallic phases occur when the number of SrTiO$_3$ layers is large or the interaction $U$ is small. In metallic phases, the mobile electrons are found in the SrTiO$_3$ layers, with near-interface electr...

Performing an analysis within density functional theory, we develop insight into the structural and electronic properties of the oxide heterostructure LaAlO3/SrTiO3. Electrostatic surface effects are decomposed from the internal lattice distortion in order to clarify their interplay. We first study the interface relaxation by a multi-layer system without surface, and the surface effects, separately, by a substrate-film system. While elongation of the TiO6 octahedra at the int...

Effects of lattice distortion on the magnetic ground state of YTiO$_3$ and LaiO$_3$ are investigated on the basis accurate tight-binding parametrization of the $t_{2g}$ electronic structure extracted from the local-density approximation. The complexity of these compounds is related with the fact that the $t_{2g}$-level splitting, caused by lattice distortions, is comparable with the energies of superexchange and spin-orbit interactions. Therefore, all these interactions are e...

The interface electronic structure of correlated LaTiO$_3$/SrTiO$_3$ superlattices is investigated by means of the charge self-consistent combination of the local density approximation (LDA) to density functional theory (DFT) with dynamical mean-field theory (DMFT). Utilizing a pseudopotential technique together with a continuous-time quantum Monte-Carlo approach, the resulting complex multiorbital electronic states are addressed in a coherent fashion beyond static mean-field...

The magnetic phase diagram of the perovskite-type Ti oxides as a function of the GdFeO3-type distortion is examined by using the Hartree-Fock analysis of a multiband d-p Hamiltonian from a viewpoint of competitions of the spin-orbit interaction, the Jahn-Teller (JT) level-splitting and spin-orbital superexchange interactions. Near the antiferromagnetic (AFM)-to-ferromagnetic (FM) phase boundary, A-type AFM [AFM(A)] and FM states accompanied by a certain type of orbital orderi...

A theory of heterostructures comprised of LaTiO$_3$ (a Mott insulator) and SrTiO$_3$ (a band insulator) is presented. The band structure of the Ti $d$% -electrons is treated with a nearest neighbor tight-binding approximation; the electric fields arising from the La$^{3+}$/Sr$^{2+}$ charge difference and the carriers are treated within a Hartree approximation; and the on-site interactions are treated by unrestricted Hartree-Fock. The phase diagram as a function of interaction...

To study digital Mott insulator LaTiO3 and band insulator SrTiO3 interfaces, we apply correlated band theory (LDA+U) to (n,m) multilayers, 1<n,m<9. If the on-site repulsion on Ti is large enough to model the magnetic insulating behavior of cubic bulk LaTiO3, the charge imbalance at the interface is found in all cases to be accommodated by disproportionation (Ti4+ + Ti3+), charge ordering, and Ti3+ d_xy-orbital ordering, with antiferromagnetic exchange coupling between the spi...

By employing first-principles electronic structure calculations we investigate nickelate superlattices [LaNiO$_3$]$_1$/[LaAlO$_3$]$_1$ and [LaNiO$_3$]$_1$/[SrTiO$_3$]$_1$ with (001) orientation under epitaxial tensile strain. Within density functional theory augmented by mean-field treatement of on-site electronic correlations, the ground states show remarkable dependence on the correlation strength and the strain. In the weakly and intermediately correlated regimes with smal...