title: Large Elasto-Optic Effect in Epitaxial PbTiO(3) Films.
abstract: First-principles calculations are performed to investigate the elasto-optic properties of four different structural phases in (001) epitaxial PbTiO(3) films under tensile strain: a tetragonal (T) phase and an orthorhombic (O) phase, which are the ground states for small and large strain, respectively, and two low-symmetry, monoclinic phases of Cm and Pm symmetries that have low total energy in the intermediate strain range. It is found that the refractive indices of the T and O phases respond differently to epitaxial strain, evidenced by a change of sign of their effective elasto-optic coefficients, and as a result of presently discovered correlations between refractive index, axial ratio, and magnitude of the ferroelectric polarization. The difference in refractive indices between T and O and the existence of such correlations naturally lead to large elasto-optic coefficients in the Cm and Pm states in the intermediate strain range, because Cm structurally bridges the T and O phases (via polarization rotation and a rapid change of its axial ratio) and Pm adopts a similar axial ratio and polarization magnitude to Cm. The present results therefore broaden the palette of functionalities of ferroelectric materials, and suggest new routes to generate systems with unprecedentedly large elasto-optic conversion.
authors.affiliation: National Laboratory of Solid State Microstructures, Collaborative Innovation Center of Advanced Microstructures, College of Engineering and Applied Sciences, Nanjing University, Nanjing 210093, China.
authors.forename: Lan
authors.initials: L
authors.lastname: Chen
authors.affiliation: Department of Physics and Institute for Nanoscience and Engineering, University of Arkansas, Fayetteville, Arkansas 72701, USA.
authors.forename: Yurong
authors.initials: Y
authors.lastname: Yang
authors.affiliation: Department of Physics and Institute for Nanoscience and Engineering, University of Arkansas, Fayetteville, Arkansas 72701, USA.
authors.forename: Zhigang
authors.initials: Z
authors.lastname: Gui
authors.affiliation: School of Materials Science and Engineering, University of New South Wales, Kensington, New South Wales 2052, Australia.
authors.forename: D
authors.initials: D
authors.lastname: Sando
authors.affiliation: Unité Mixte de Physique, CNRS, Thales, Univ. Paris-Sud, Université Paris-Saclay, 91767 Palaiseau, France.
authors.forename: M
authors.initials: M
authors.lastname: Bibes
authors.affiliation: National Laboratory of Solid State Microstructures, Collaborative Innovation Center of Advanced Microstructures, College of Engineering and Applied Sciences, Nanjing University, Nanjing 210093, China.
authors.forename: X K
authors.initials: XK
authors.lastname: Meng
authors.affiliation: Department of Physics and Institute for Nanoscience and Engineering, University of Arkansas, Fayetteville, Arkansas 72701, USA.
authors.forename: L
authors.initials: L
authors.lastname: Bellaiche