title: Engineered Unique Elastic Modes at a BaTiO_{3}/(2×1)-Ge(001) Interface.
abstract: The strong interaction at an interface between a substrate and thin film leads to epitaxy and provides a means of inducing structural changes in the epitaxial film. These induced material phases often exhibit technologically relevant electronic, magnetic, and functional properties. The 2×1 surface of a Ge(001) substrate applies a unique type of epitaxial constraint on thin films of the perovskite oxide BaTiO_{3} where a change in bonding and symmetry at the interface leads to a non-bulk-like crystal structure of the BaTiO_{3}. While the complex crystal structure is predicted using first-principles theory, it is further shown that the details of the structure are a consequence of hidden phases found in the bulk elastic response of the BaTiO_{3} induced by the symmetry of forces exerted by the germanium substrate.
authors.affiliation: Center for Research on Interface Structures and Phenomena, Yale University, New Haven, Connecticut 06520, USA.
authors.forename: D P
authors.initials: DP
authors.lastname: Kumah
authors.affiliation: Center for Research on Interface Structures and Phenomena, Yale University, New Haven, Connecticut 06520, USA.
authors.forename: M
authors.initials: M
authors.lastname: Dogan
authors.affiliation: Center for Research on Interface Structures and Phenomena, Yale University, New Haven, Connecticut 06520, USA.
authors.forename: J H
authors.initials: JH
authors.lastname: Ngai
authors.affiliation: Center for Research on Interface Structures and Phenomena, Yale University, New Haven, Connecticut 06520, USA.
authors.forename: D
authors.initials: D
authors.lastname: Qiu
authors.affiliation: Argonne National Laboratory, Advanced Photon Source, Argonne, Illinois 60439, USA.
authors.forename: Z
authors.initials: Z
authors.lastname: Zhang
authors.affiliation: Brookhaven National Laboratory, Center for Functional Nanomaterials, Upton, New York 11973, USA.
authors.forename: D
authors.initials: D
authors.lastname: Su
authors.affiliation: Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
authors.forename: E D
authors.initials: ED
authors.lastname: Specht
authors.affiliation: Center for Research on Interface Structures and Phenomena, Yale University, New Haven, Connecticut 06520, USA.
authors.forename: S
authors.initials: S
authors.lastname: Ismail-Beigi
authors.affiliation: Center for Research on Interface Structures and Phenomena, Yale University, New Haven, Connecticut 06520, USA.
authors.forename: C H
authors.initials: CH
authors.lastname: Ahn
authors.affiliation: Center for Research on Interface Structures and Phenomena, Yale University, New Haven, Connecticut 06520, USA.
authors.forename: F J
authors.initials: FJ
authors.lastname: Walker