The 354th forum: Topological Vortex Domains in Quantum Materials
Rutgers Center for Emergent Materials
Department of Physics & Astronomy, Rutgers University
报告人简介：Prof. Cheong has made ground-breaking contributions to the research field of enhanced physical functionalities in complex materials originating from collective correlations and collective phase transitions such as colossal magnetoresistive and colossal magnetoelectric effects in complex oxides. He has also made pivotal contributions to mesoscopic self-organization in solids, including the nanoscale charge stripe formation, mesoscopic electronic phase separation in mixed valent transition metal oxides, and the formation of topological vortex domains in multiferroics, which was found to be synergistically relevant to mathematics (graph theory) and even cosmology. He has published more than 800 scientific papers, and the total citation is more than 48,000 (Web of Science: six papers cited more than 1000 times, and his h-index is 104). His educational background includes mathematics in college, string theory (about three years) in graduate school, and solid state physics for Ph. D.. He has worked at Los Alamos National Laboratory, AT&T Bell Laboratories, and Rutgers Center for Emergent Materials (RCEM), Rutgers University. He is currently the director of center for Quantum Materials Synthesis, the director of Rutgers Center for Emergent Materials, a Henry Rutgers Professor and a Board of Governors Professor at Rutgers, a Distinguished Visiting Professor at Postech in S. Korea as well as in Nanjing University in China. His work on complex oxides has been recognized through various prizes, including the 2007 Hoam Prize sponsored by Samsung, the KBS 2009 Global Korean Award, and the 2010 James C. McGroddy Prize for New Materials sponsored by IBM.
报告摘要：Engineering of domains and domain boundaries is quintessential for technological exploitation of numerous functional materials. However, it has only recently realized that the configuration of these domains/domain boundaries can have non-trivial topology. We will discuss a new topological classification scheme of domain/domain boundary configurations with Ising-type or two-dimensional order parameters: Zm×Zn domains (m directional variants and n translational antiphases) and Zl vortices (where l number of domains and that of domain boundaries merge). This classification, with the concept of topological protection and topological charge conservation, has been applied to a wide range of materials such as improper ferroelectric R(Mn,Fe)O3, antipolar In(Mn,Ga)O3, hybrid improper ferroelectric (Ca,Sr)3Ti2O7, chiral (and ferromagnetic) Fe1/3TaS2, magnetic-superconducting Sr2VO3FeAs, magnetic a-Fe2O3, and CDW systems such as 2H-TaSe2. We will also discuss the emergent physical properties of domain boundaries, distinct from those of domains. The presented topological consideration provides a basis in understanding the formation, kinetics, manipulation and property optimization of domains/domain boundaries in quantum materials.