[Icqm_seminar] 5.26 weekly seminar

报告题目： Broken Symmetry and Magnetic Skyrmions 报告人： Sunxiang Huang 报告时间： 2014.5.26（周一）下午4:00 报告地点：理科5号楼607 联系人：林熙 Abstract: Broken symmetry is a fundamental concept in physics. The broken symmetries at phase transitions, such as those at the gaseous/solid and the paramagnetic/ferromagnetic transitions, are familiar examples. In cubic B20 magnets, however, it is the inversion symmetry and the 4-fold rotation symmetry that are broken. The broken inversion symmetry leads to the Dzyaloshinskii-Moriya (D-M) interaction, which dictates not an aligned ground state but a spin helix, and in addition, an exotic magnetic skyrmion state with a new type of topological spin texture. Magnetic skyrmions, with a double-twist spin structure on the nanometer scale, carry a topological charge and a Berry phase in real space. Magnetic skyrmions not only provide a novel route to study the topological nature of magnetic defects but also exhibit spectacular static and dynamic properties. Among the various unusual properties, I’ll describe our experimental results of the direct consequence of the broken rotation symmetry in the electric transport properties, and the determination of the intrinsic resistance of the spin helix. In bulk B20 crystals, the skyrmion state exists only in a very small region in the phase space of a few K and a narrow magnetic field range, which is not amenable to exploration of magnetic skyrmions for new spintronic phenomena let alone devices. I will describe the realization of epitaxial B20 FeGe thin films with greatly expanded skyrmion state in phase space covering the entire temperature range up to the Curie temperature and in a much larger field range. About the speaker: Sunxiang Huang got his Bachlor degree from the University of Science and Technology of China in 2003 and his Ph.D from Johns Hopkins University (JHU) in 2011. Since 2011 to present, he has been the Postdoctoral Fellow in JHU.Dr. Huang has accepted University of Miami's assistant professor position.