When 10:30 AM - 11:30 AM Nov 02, 2018
Where 1571 G.G. Brown
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Computational Understanding and Discovery of Polar States in Ferroelectric Heterostructures Using Phase-field Method


Long-Qing Chen
Department of Materials Science & Enginering and Materials Research Institute, Penn State University

This presentation will discuss the applications of the phase-field method to understanding and discovering new mesoscale polar states that might emerge from nanoscale ferroelectric heterostructures subject to different mechanical and electric boundary conditions. As an example, the determination of thermodynamic conditions and geometric length scales leading to the formation of ordered polar vortex lattice as well as mixed states of regular domains and vortices in ferroelectric superlattices of PbTiO3/SrTiO3using phase-field simulations and analytical theory will be presented. Switching of these vortex lattice states might produce other transient polar states such as polar skyrmions.  It is shown that the stability of these vortex lattices involves an intimate competition between long-range electrostatic, long-range elastic, and short-range polarization gradient-related interactions leading to both an upper- and a lower- bound to the length scale at which these states can be observed.  We further predicted the periodicity phase diagrams that show excellent agreements with experimental observations by collaborators.

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