title: Suppression of the critical thickness threshold for conductivity at the LaAlO3/SrTiO3 interface.
abstract: Perovskite materials engineered in epitaxial heterostructures have been intensely investigated during the last decade. The interface formed by an LaAlO3 thin film grown on top of a TiO2-terminated SrTiO3 substrate hosts a two-dimensional electronic system and has become the prototypical example of this field. Although controversy exists regarding some of its physical properties and their precise origin, it is universally found that conductivity only appears beyond an LaAlO3 thickness threshold of four unit cells. Here, we experimentally demonstrate that this critical thickness can be reduced to just one unit cell when a metallic film of cobalt is deposited on top of LaAlO3. First-principles calculations indicate that Co modifies the electrostatic boundary conditions and induces a charge transfer towards the Ti 3d bands, supporting the electrostatic origin of the electronic system at the LaAlO3/SrTiO3 interface. Our results expand the interest of this low-dimensional oxide system from in-plane to perpendicular transport and to the exploration of elastic and inelastic tunnel-type transport of (spin-polarized) carriers.
authors.affiliation: Unité Mixte de Physique CNRS/Thales, 1 Avenue A. Fresnel, 91767 Palaiseau, France and Université Paris-Sud, 91405 Orsay, France.
authors.forename: E
authors.initials: E
authors.lastname: Lesne
authors.affiliation: Unité Mixte de Physique CNRS/Thales, 1 Avenue A. Fresnel, 91767 Palaiseau, France and Université Paris-Sud, 91405 Orsay, France.
authors.forename: N
authors.initials: N
authors.lastname: Reyren
authors.affiliation: Department of Earth and Environmental Sciences, Section Crystallography and Center of Nanoscience (CENS), University of Munich, Theresienstrasse 41, DE-80333 Munich, Germany.
authors.forename: D
authors.initials: D
authors.lastname: Doennig
authors.affiliation: Unité Mixte de Physique CNRS/Thales, 1 Avenue A. Fresnel, 91767 Palaiseau, France and Université Paris-Sud, 91405 Orsay, France.
authors.forename: R
authors.initials: R
authors.lastname: Mattana
authors.affiliation: Unité Mixte de Physique CNRS/Thales, 1 Avenue A. Fresnel, 91767 Palaiseau, France and Université Paris-Sud, 91405 Orsay, France.
authors.forename: H
authors.initials: H
authors.lastname: Jaffrès
authors.affiliation: Unité Mixte de Physique CNRS/Thales, 1 Avenue A. Fresnel, 91767 Palaiseau, France and Université Paris-Sud, 91405 Orsay, France.
authors.forename: V
authors.initials: V
authors.lastname: Cros
authors.affiliation: Unité Mixte de Physique CNRS/Thales, 1 Avenue A. Fresnel, 91767 Palaiseau, France and Université Paris-Sud, 91405 Orsay, France.
authors.forename: F
authors.initials: F
authors.lastname: Petroff
authors.affiliation: Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin, BP 48, 91192 Gif-sur-Yvette, France.
authors.forename: F
authors.initials: F
authors.lastname: Choueikani
authors.affiliation: Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin, BP 48, 91192 Gif-sur-Yvette, France.
authors.forename: P
authors.initials: P
authors.lastname: Ohresser
authors.affiliation: 1] Department of Earth and Environmental Sciences, Section Crystallography and Center of Nanoscience (CENS), University of Munich, Theresienstrasse 41, DE-80333 Munich, Germany [2] Faculty of Physics, University of Duisburg-Essen, D-47048 Duisburg, Germany.
authors.forename: R
authors.initials: R
authors.lastname: Pentcheva
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: 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