报告题目：How to dress a metal? Ultrafast coherent spectroscopy and microscopy of quasiparticle
报告人：Dynamics Hrvoje Petek (University of Pittsburgh)
报告时间: 2019年3月6日（周三）下午 4:00-5:00
报告地点: 物理学院新楼五楼多功能厅
Abstract:
An intense optical field interacting with a metal surface can excite single-particle and collective excitations, but it should also be understood that it acts as a coherent perturbation. If the optical field coupling between the ground and excited states is sufficiently strong, it causes an AC Stark shifting of the resonant bands by the Rabi frequency. This dressing of the electronic structure by a resonant optical field is well established in gas phase atom and molecular spectroscopy, but we show for the first time that it can modify the electronic structure of solid surfaces. Such a coherent modification of the band structure in solid state is surprising, because of ultrafast dephasing of optical coherence, but similar effects are anticipated to optically induce superconductivity. Another method how we use to modify the electronic properties of a metal is by optically introducing a topological defect. By tailoring the geometrical phase of a surface plasmon polariton field, we generate a topological spin texture corresponding to a new quasiparticle, a spin skyrmion, which breaks the time-inversion symmetry on 20 fs time scale. We anticipate that such novel quasiparticles may find use in topologically protected quantum information processing.
Speaker:
Prof. Hrvoje Petek is the RK Mellon Chair Professor at the University of Pittsburgh. He received his B.S. in 1980 at Massachusetts Institute of Technology, and Ph.D. in 1985 at University of California, Berkeley. In 2000, he became a Professor of Physics, and later Professor of Chemistry, at the University of Pittsburgh. He was elected as a Fellow of the American Physical Society in 2003. In 2014, he was appointed as the Richard King Mellon Chair Professor of Physics and Astronomy, the most prestigious professor Chair at the University. In 2016, he was elected as a fellow of American Association for the Advancement of Science. In 2019, he was awarded with the Ahmed Zewail Award in Ultrafast Science and Technology of the American Chemical Society, the most important award in the field of ultrafast dynamics. Dr. Petek’s research interests focus on nonequilibrium electronic phenomena at surfaces, interfaces and in solids; ultrafast plasmonics in metallic nanostructures; ultrafast microscopy of coherent excitations in solids and the Surface femtochemistry and photocatalysis. He is a pioneer in the coherent ultrafast microscopy and microscopy of solid-state materials. From 2006, he has been the Editor-in-Chief of Progress in Surface Science.
邀请人：丰敏教授
