题目：Prediction of 2D Topological Materials
Department of Materials Science and Engineering, University of Utah, Salt Lake City,
UT 84112, USA
Topological insulators (TIs) are a recently discovered class of materials having insulating bulk electronic states but conducting boundary states distinguished by nontrivial topology. So far, several generations of TIs have been theoretically predicted and experimentally confirmed. In this talk, I willfirst present our recent theoretical prediction of a new family of 2D“organic” TIs made of organometallic lattices [1-4], based on first-principles calculations and tight-binding model analyses. Designed by assembling molecular building blocks of organometallic compounds with strong spin-orbit coupling into a hexagonal and Kagome lattices, these new classes of organic topological materials are shown to exhibit nontrivial topological edge states in both Dirac bands [1,4] and flat Chen bands (so-called fractional Chern insulator) [2,4], which are robust against significant lattice strain. Realization of half metallic state and anomalous quantum Hall effect in magnetic organic TIs with the inclusion of transition metal elements will also be discussed . Then, I will discuss our most recent studies of large-gap topological phases on conventional semiconductor surfaces [5,6]. By epitaxial growth of heavy metal elements such as Bi on a halogenated Si(111) surface, a large-gap (~0.8 eV) quantum spin Hall state  is shown to originate from an intriguing substrate orbital filtering effect that critically select the orbital composition around the Fermi level to form different topological phases. Furthermore, growth of transition metals such as W leads to formation of a new form of 2D material, so-called sd2 graphene , which is characterized with bond-centered electronic hopping that transforms the apparent atomic hexagonal lattice into the physics of Kagome lattice to exhibit room-temperature quantum anomalous Hall state. We envision that these findings will greatly broaden the scientific scope and technological impact of emerging topological materials.
 Z. F. Wang, Z. Liu and F. Liu,“Organic topological insulators in organometallic lattices”, Nature Commun.4, 1471 (2013).
 Z. Liu, Z. F. Wang, J.-W.Mei, Y. Wu and F. Liu, “Flat Chern Band in a Two-Dimensional Organometallic Framework”, Phys. Rev. Lett.110, 106804 (2013).
 Z. F. Wang, Z. Liu and F. Liu, “Quantum anomalous Hall effect in 2D organic topological insulator”, Phys. Rev. Lett. 110, 196801 (2013).
 Z. F. Wang, N. Su and F. Liu, “Prediction of a Two-Dimensional Organic Topological Insulator”, Nano Letters, 13, 2842 (2013).
 M. Zhou, W. Ming, Z. Liu, Z. Wang, P. Li, F. Liu, “Epitaxial growth of large-gap quantum spin Hall insulator on semiconductor surface”, Proc. Natl. Acad. Sci., 111, 14378 (2014).
 M. Zhou, Z. Liu, W. Ming, Z. Wang, and F. Liu, “sd2 Graphene: Kagome Band in Hexagonal lattice”, Phys. Rev. Lett. 113, 236802 (2014).
刘锋，国际著名材料物理学家，美国犹他大学材料系终身教授、系主任，美国物理学会会士 (Fellow, American Physical Society)，物理评论快报编辑 (Divisional Associate Editor, Physical Review Letters),曾获德国洪堡高级研究奖，澳大利亚国际教授奖，中国基金委海外杰青奖，中科院海外知名学者奖，美国能源部材料和工程物理研究奖。已发表200多篇学术论文，8章丛书和18篇特邀综述论文，在世界各地做过200多场特邀学术报告。刘锋教授还是10多项专利的发明人；2009年他的一项专利被美国Sorensen Capital投资公司买断并成立了Solan公司，研发石墨烯在太阳能和光电器件中的应用，刘锋教授现任该公司首席科学顾问。2011年，刘锋教授的团队发明了纳烯(Nanoxene)复合材料并创办了Life-E公司，目前正在开拓纳烯材料技术在电热产品中的应用。