title: Hybridization-controlled charge transfer and induced magnetism at correlated oxide interfaces.
abstract: At interfaces between conventional materials, band bending and alignment are classically controlled by differences in electrochemical potential. Applying this concept to oxides in which interfaces can be polar and cations may adopt a mixed valence has led to the discovery of novel two-dimensional states between simple band insulators such as LaAlO3and SrTiO3. However, many oxides have a more complex electronic structure, with charge, orbital and/or spin orders arising from strong Coulomb interactions between transition metal and oxygen ions. Such electronic correlations offer a rich playground to engineer functional interfaces but their compatibility with the classical band alignment picture remains an open question. Here we show that beyond differences in electron affinities and polar effects, a key parameter determining charge transfer at correlated oxide interfaces is the energy required to alter the covalence of the metal-oxygen bond. Using the perovskite nickelate (RNiO3) family as a template, we probe charge reconstruction at interfaces with gadolinium titanate GdTiO3. X-ray absorption spectroscopy shows that the charge transfer is thwarted by hybridization effects tuned by the rare-earth (R) size. Charge transfer results in an induced ferromagnetic-like state in the nickelate, exemplifying the potential of correlated interfaces to design novel phases. Further, our work clarifies strategies to engineer two-dimensional systems through the control of both doping and covalence.
authors.affiliation: Unité Mixte de Physique CNRS/Thales, 1 avenue A. Fresnel, 91767 Palaiseau, France, and Université Paris-Sud, 91405 Orsay, France.
authors.forename: M N
authors.initials: MN
authors.lastname: Grisolia
authors.affiliation: Unité Mixte de Physique CNRS/Thales, 1 avenue A. Fresnel, 91767 Palaiseau, France, and Université Paris-Sud, 91405 Orsay, France.
authors.forename: J
authors.initials: J
authors.lastname: Varignon
authors.affiliation: GFMC, Departamento Física Aplicada III, Universidad Complutense Madrid, 28040 Madrid, Spain, and Laboratorio de Heteroestructuras con aplicación en Spintronica, Unidad Asociada CSIC/Universidad Complutense de Madrid, Sor Juana Inés de la Cruz, 3, 28049 Madrid, Spain.
authors.forename: G
authors.initials: G
authors.lastname: Sanchez-Santolino
authors.affiliation: Helmholtz-Zentrum Berlin für Materialen & Energie, Albert-Einstein-Strasse 15, 12489 Berlin, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Arora
authors.affiliation: Helmholtz-Zentrum Berlin für Materialen & Energie, Albert-Einstein-Strasse 15, 12489 Berlin, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Valencia
authors.affiliation: Materials Science & Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.|GFMC, Departamento Física Aplicada III, Universidad Complutense Madrid, 28040 Madrid, Spain, and Laboratorio de Heteroestructuras con aplicación en Spintronica, Unidad Asociada CSIC/Universidad Complutense de Madrid, Sor Juana Inés de la Cruz, 3, 28049 Madrid, Spain.
authors.forename: M
authors.initials: M
authors.lastname: Varela
authors.affiliation: Helmholtz-Zentrum Berlin für Materialen & Energie, Albert-Einstein-Strasse 15, 12489 Berlin, Germany.|Institut für Experimentalphysik/Festkörperphysik, Ruhr-Universität Bochum, 44780 Bochum, Germany.
authors.forename: R
authors.initials: R
authors.lastname: Abrudan
authors.affiliation: Helmholtz-Zentrum Berlin für Materialen & Energie, Albert-Einstein-Strasse 15, 12489 Berlin, Germany.
authors.forename: E
authors.initials: E
authors.lastname: Weschke
authors.affiliation: Helmholtz-Zentrum Berlin für Materialen & Energie, Albert-Einstein-Strasse 15, 12489 Berlin, Germany.
authors.forename: E
authors.initials: E
authors.lastname: Schierle
authors.affiliation: Synchrotron SOLEIL, L'Orme des Merisiers Saint-Aubin, BP 48, 91192 Gif-sur-Yvette, France.
authors.forename: J E
authors.initials: JE
authors.lastname: Rault
authors.affiliation: Synchrotron SOLEIL, L'Orme des Merisiers Saint-Aubin, BP 48, 91192 Gif-sur-Yvette, France.
authors.forename: J-P
authors.initials: JP
authors.lastname: Rueff
authors.affiliation: Unité Mixte de Physique CNRS/Thales, 1 avenue A. Fresnel, 91767 Palaiseau, France, and Université Paris-Sud, 91405 Orsay, France.
authors.forename: A
authors.initials: A
authors.lastname: Barthélémy
authors.affiliation: GFMC, Departamento Física Aplicada III, Universidad Complutense Madrid, 28040 Madrid, Spain, and Laboratorio de Heteroestructuras con aplicación en Spintronica, Unidad Asociada CSIC/Universidad Complutense de Madrid, Sor Juana Inés de la Cruz, 3, 28049 Madrid, Spain.
authors.forename: J
authors.initials: J
authors.lastname: Santamaria
authors.affiliation: Unité Mixte de Physique CNRS/Thales, 1 avenue A. Fresnel, 91767 Palaiseau, France, and Université Paris-Sud, 91405 Orsay, France.
authors.forename: M
authors.initials: M
authors.lastname: Bibes