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<span style="font-size:10.5pt; font-family:"Arial","sans-serif"; color:#1F497D">***** Seminar *****</span><span style="color:#1F497D"></span></p>
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<b><span style="font-size:16.0pt; color:#1F497D">Department of Electrical and Computer Engineering</span></b><span style="font-size:16.0pt; color:#1F497D"></span></p>
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<b><span style="font-size:16.0pt; color:#1F497D">Materials Engineering Program</span></b></p>
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<b><span style="font-size:14.0pt; color:#1F497D">Center for Integrated Bio and Nano Systems</span></b></p>
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<b><span style="font-size:14.0pt; color:#1F497D"> Feb. 22, 2019</span></b><span style="font-size:14.0pt; color:#1F497D"></span></p>
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<b><span style="font-size:14.0pt; color:#1F497D">10:30 a.m., Room: CBB 108 </span>
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<b><span style="font-size:18.0pt; color:#1F497D">Understanding Structural Phase Transition and Light-Matter Interaction in 2D Materials from First-Principles Theory </span></b></p>
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<span style="font-size:18.0pt; color:#1F497D">Xiaofeng Qian</span></p>
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<span style="font-size:16.0pt; color:#1F497D">Texas A&M University</span></p>
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<b><span style="color:#1F497D">Abstract</span></b><span style="font-size:11.0pt; font-family:"Calibri","sans-serif"; color:#1F497D">:</span><span style="color:#1F497D"> 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.
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<b><span style="color:#1F497D">Bio</span></b><span style="color:#1F497D">: 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.
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<span style="color:#1F497D">Contact Prof. Cunjiang Yu <cyu13@Central.UH.EDU> if you would like to meet with Dr. Qian.</span></p>
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