Attosecond (10-18 s) science (attoscience) is a new frontier of science that allows us to investigate the fastest dynamics happening in atoms, molecules and materials. In this talk, I will give a general introduction about what we can learn from attoscience studies and how the dynamics on the attosecond timescales can be measured in experiments. High-order harmonic generation (HHG) so far have served as one of the most powerful tools for such studies. As an example of attoscience study, I will present our recent efforts in JILA to measure attosecond electron dynamics in transition metals by combining HHG light source with angle-resolved photoelectron spectroscopy (ARPES). In this work, we for the first time revealed the strong influence of material band structure on the attosecond electron dynamics in materials, enabled by good energy resolution and polarization, angle-dependent measurements. At the same time, we investigated the electron-electron interactions (screening and scattering) on this shortest timescale ever accessible in a material.

报告人简介：Zhensheng joined Kapteyn-Murnane group as a research associate in August, 2014. He got his BA and MS degrees in Physics from Fudan University (Shanghai, China) in 2008. Then, he moved to Michigan State University to pursue his Ph. D degree, and was awarded in 2014. At MSU, he worked with Dr. Chong-yu Ruan on the ultrafast electron diffraction, which enables the studies on the materials’ structural dynamics with a sub-ps temporal resolution. At K-M group, his research interest switches to the ultrafast dynamics of the electronic structures in the solid-state materials that exhibit exotic emergent phenomena, which includes transition metal oxides, charge-density-wave materials, high-temperature superconductors, etc. From the time-resolved optical and electronic spectroscopy, he intends to resolve the fundamental driving mechanisms of these emergent and important phenomena. His researches are enabled by the recent development of the coherent EUV source at K-M group, which serves as a powerful light source for the experiments like angle-resolved photoemission spectroscopy (ARPES) and other soft X-ray spectroscopy.