RESUMEN
Coherent and epitaxial interfaces permit the realization of electric field driven devices controlled by atomic-scale structural and electronic effects at interfaces. Compared to conventional field effect devices where channel conductivity is modulated by carrier density modification, the propagation of atomic-scale distortions across an interface can control the atomic scale bonding, interatomic electron tunneling rates and thus the mobility of the channel material. We use first-principles theory to design an atomically abrupt epitaxial perovskite heterostructure involving an oxide ferroelectric (PbZr0.2Ti0.8O3) and conducting oxide channel (LaNiO3) where coupling of polar atomic motions to structural distortions can induce large, reversible changes in the channel mobility. We fabricate and characterize the heterostructure and measure record values, larger than 1000%, for the conductivity modulation. Our results describe how purely interfacial effects can be engineered to deliver unique electronic device properties and large responses to external fields.
RESUMEN
We experimentally demonstrate a novel approach to substantially modify orbital occupations and symmetries in electronically correlated oxides. In contrast to methods using strain or confinement, this orbital tuning is achieved by exploiting charge transfer and inversion symmetry breaking using atomically layered heterostructures. We illustrate the technique in the LaTiO_{3}-LaNiO_{3}-LaAlO_{3} system; a combination of x-ray absorption spectroscopy and ab initio theory reveals electron transfer and concomitant polar fields, resulting in a â¼50% change in the occupation of Ni d orbitals. This change is sufficiently large to remove the orbital degeneracy of bulk LaNiO_{3} and creates an electronic configuration approaching a single-band Fermi surface. Furthermore, we theoretically show that such three-component heterostructuring is robust and tunable by choice of insulator in the heterostructure, providing a general method for engineering orbital configurations and designing novel electronic systems.
RESUMEN
Metallic electronic transport in nickelate heterostructures can be induced and confined to two dimensions (2D) by controlling the structural parameters of the nickel-oxygen planes.
RESUMEN
We carry out a first-principles theoretical study of the magnetically induced polarization in orthorhombic TbMnO3, a prototypical material in which a cycloidal-spin structure generates an electric polarization via the spin-orbit interaction. We compute both the electronic and the lattice-mediated contributions to the polarization and find that the latter is strongly dominant. We analyze the spin-orbit induced forces and lattice displacements from both atomic and mode-decomposition viewpoints, and show that a simple model based on nearest Mn-Mn neighbor Dzyaloshinskii-Moriya interactions is not able to account fully for the results. The direction and magnitude of our computed polarization are in good agreement with experiment.