title: Giant optical enhancement of strain gradient in ferroelectric BiFeO3 thin films and its physical origin.
abstract: Through mapping of the spatiotemporal strain profile in ferroelectric BiFeO3 epitaxial thin films, we report an optically initiated dynamic enhancement of the strain gradient of 10(5)-10(6) m(-1) that lasts up to a few ns depending on the film thickness. Correlating with transient optical absorption measurements, the enhancement of the strain gradient is attributed to a piezoelectric effect driven by a transient screening field mediated by excitons. These findings not only demonstrate a new possible way of controlling the flexoelectric effect, but also reveal the important role of exciton dynamics in photostriction and photovoltaic effects in ferroelectrics.
authors.affiliation: Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA.
authors.forename: Yuelin
authors.initials: Y
authors.lastname: Li
authors.affiliation: Department of Applied Physics, Stanford University, Stanford, CA 94305, USA.
authors.forename: Carolina
authors.initials: C
authors.lastname: Adamo
authors.affiliation: Department of Materials Science and Engineering &Materials Science Program, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA.
authors.forename: Pice
authors.initials: P
authors.lastname: Chen
authors.affiliation: Department of Materials Science and Engineering &Materials Science Program, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA.
authors.forename: Paul G
authors.initials: PG
authors.lastname: Evans
authors.affiliation: Department of Materials Science &Engineering, and Institute of Materials Science, University of Connecticut, Storrs, CT 06269-3136, USA.
authors.forename: Serge M
authors.initials: SM
authors.lastname: Nakhmanson
authors.affiliation: Argonne Leadership Computing Facility, Argonne National Laboratory, Argonne, Illinois 60439, USA.
authors.forename: William
authors.initials: W
authors.lastname: Parker
authors.affiliation: Department of Chemistry, Northwestern University, Evanston, IL 60208, USA.
authors.forename: Clare E
authors.initials: CE
authors.lastname: Rowland
authors.affiliation: Department of Chemistry, Northwestern University, Evanston, IL 60208, USA.|Center for Nanoscale Materials, Argonne National Laboratory, Argonne, Illinois 60439, USA.
authors.forename: Richard D
authors.initials: RD
authors.lastname: Schaller
authors.affiliation: Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853, USA.|Kavli Institute at Cornell for Nanoscale Science, Ithaca, New York 14853, USA.
authors.forename: Darrell G
authors.initials: DG
authors.lastname: Schlom
authors.affiliation: Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA.
authors.forename: Donald A
authors.initials: DA
authors.lastname: Walko
authors.affiliation: Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA.
authors.forename: Haidan
authors.initials: H
authors.lastname: Wen
authors.affiliation: Department of Materials Science and Engineering &Materials Science Program, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA.
authors.forename: Qingteng
authors.initials: Q
authors.lastname: Zhang