title: Domain topology and domain switching kinetics in a hybrid improper ferroelectric.
abstract: Charged polar interfaces such as charged ferroelectric walls or heterostructured interfaces of ZnO/(Zn,Mg)O and LaAlO3/SrTiO3, across which the normal component of electric polarization changes suddenly, can host large two-dimensional conduction. Charged ferroelectric walls, which are energetically unfavourable in general, were found to be mysteriously abundant in hybrid improper ferroelectric (Ca,Sr)3Ti2O7 crystals. From the exploration of antiphase boundaries in bilayer-perovskites, here we discover that each of four polarization-direction states is degenerate with two antiphase domains, and these eight structural variants form a Z4 × Z2 domain structure with Z3 vortices and five distinct types of domain walls, whose topology is directly relevant to the presence of abundant charged walls. We also discover a zipper-like nature of antiphase boundaries, which are the reversible creation/annihilation centres of pairs of two types of ferroelectric walls (and also Z3-vortex pairs) in 90° and 180° polarization switching. Our results demonstrate the unexpectedly rich nature of hybrid improper ferroelectricity.
authors.affiliation: Rutgers Center for Emergent Materials, Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey 08854, USA.
authors.forename: F-T
authors.initials: FT
authors.lastname: Huang
authors.affiliation: Department of Materials Science and Engineering, Pennsylvania State University, University Park, Pennsylvania 16802, USA.
authors.forename: F
authors.initials: F
authors.lastname: Xue
authors.affiliation: Rutgers Center for Emergent Materials, Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey 08854, USA.
authors.forename: B
authors.initials: B
authors.lastname: Gao
authors.affiliation: Laboratory for Pohang Emergent Materials, Max Plank POSTECH Center for Complex Phase Materials, Pohang University of Science and Technology, Pohang 790-784, Korea.
authors.forename: L H
authors.initials: LH
authors.lastname: Wang
authors.affiliation: Laboratory for Pohang Emergent Materials, Max Plank POSTECH Center for Complex Phase Materials, Pohang University of Science and Technology, Pohang 790-784, Korea.
authors.forename: X
authors.initials: X
authors.lastname: Luo
authors.affiliation: Rutgers Center for Emergent Materials, Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey 08854, USA.
authors.forename: W
authors.initials: W
authors.lastname: Cai
authors.affiliation: Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, USA.
authors.forename: X-Z
authors.initials: XZ
authors.lastname: Lu
authors.affiliation: Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, USA.
authors.forename: J M
authors.initials: JM
authors.lastname: Rondinelli
authors.affiliation: Department of Materials Science and Engineering, Pennsylvania State University, University Park, Pennsylvania 16802, USA.
authors.forename: L Q
authors.initials: LQ
authors.lastname: Chen
authors.affiliation: Rutgers Center for Emergent Materials, Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey 08854, USA.|Laboratory for Pohang Emergent Materials, Max Plank POSTECH Center for Complex Phase Materials, Pohang University of Science and Technology, Pohang 790-784, Korea.
authors.forename: S-W
authors.initials: SW
authors.lastname: Cheong