| Date | 18th Dec. 2018 |
| Time | 14:30-15:30 |
| Venue | Room 118, Building 12, Yuquan Campus |
| Speaker | Prof. Chen Long-Qing (Department of Materials Science and Engineering and Materials Research Institute, The Pennsylvania State University) |
| Abstract | 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/SrTiO3 using 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. |
| Speaker | Chen is the Donald W. Hamer Professor of Materials Science and Engineering, Professor of Engineering Science and Mechanics, and Professor of Mathematics at Penn State. He received his Ph.D. from MIT in Materials Science and Engineering in 1990 and joined the faculty at Penn State in 1992. He has published over 600 papers in the area of computational microstructure evolution and multiscale modeling of structural metallic alloys, functional oxides, and energy materials. For his research accomplishments, he has received numerous awards including the 2014 Materials Research Society (MRS) Materials Theory Award, a Guggenheim Fellowship, a Humboldt Research Award, the 2011 The Minerals, Metals and Materials Society (TMS) EMPMD Distinguished Scientist Award, and ASM International Silver Medal. He is a Fellow of TMS, MRS, American Physical Society (APS), The American Association for the Advancement of Science (AAAS), American Ceramic Society (ACerS), and ASM International (ASM). He is a Clarivate Analytics Highly Cited Researcher and the Editor-in-Chief for npj Computational Materials published by Springer-Nature. |
