[CCoE Notice] Seminar: Understanding Structural Phase Transition and Light-Matter Interaction in 2D Materials from First-Principles Theory * CBB 108 * 10:30 am, Friday, Feb. 22, 2019 * Xiaofeng Qian * Texas A&M University *

[Knudsen, Rachel W]

***** Seminar *****
Department of Electrical and Computer Engineering
Materials Engineering Program
Center for Integrated Bio and Nano Systems
  Feb. 22, 2019
10:30 a.m., Room: CBB 108
Understanding Structural Phase Transition and Light-Matter Interaction in 2D Materials from First-Principles Theory
Xiaofeng Qian
Texas A&M University
Abstract: The rapid advances in electronic structure theory and high-performance computing in the last few decades have led to deeper understandings and more accurate predictions of materials properties.  In this talk, I will highlight our recent theoretical effort on understanding intriguing structural phase transition and light-matter interaction in 2D materials.  First, I will introduce our recent discovery of 2D (multi)ferroicity. For example, monolayer group IV monochalcogenides exhibit strongly-coupled, large in-plane spontaneous ferroelectric polarization and spontaneous ferroelastic lattice strain as well as highly anisotropic optical properties. First-principles based machine-learning force field was developed to help understand structural phase transition and domain switching in 2D ferroelectric-ferroelastic materials. Second, I will present our recent development of first-principles nonlinear optics and demonstrate its application on the understanding of nonlinear optical responses in 2D materials. In particular, transition metal dichalcogenides and group IV monochalcogenides possess strong nonlinear optical responses that are correlated with multiferroic orders. I will discuss the underlying mechanism from the relationship between nonlinear optical responses and Berry curvature/Berry connection, which is ultimately governed by intrinsic symmetry. These findings suggest that 2D materials may enable applications such as ultrathin nonvolatile memory and nonlinear optoelectronics.
Bio: Dr. Xiaofeng Qian is Assistant Professor in the Department of Materials Science and Engineering at Texas A&M University. He received his Ph.D. in Nuclear Science and Engineering at MIT in 2008. He then worked with Prof. Nicola Marzari and Ju Li as postdoc at MIT. In 2015, he joined Texas A&M University. Dr. Qian has published 40 journal articles and filed two patents, and he received the NSF CAREER award in 2018. His research areas include first-principles electronic structure theory, light-matter interaction, quantum transport, photovoltaics, topological phase transition, and strain engineering, with focus placed on multiferroics, low-dimensional materials, and topological materials.
Contact Prof. Cunjiang Yu  <cyu13 at Central.UH.EDU> if you would like to meet with Dr. Qian.
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