报告题目：Revealing Electron-Phonon Coupling and Interplay in Strongly Correlated Quantum Materials Using Ultrafast Electrons
报 告 人：Yimei Zhu，Department of Condensed Matter Physics，Brookhaven National Laboratory
报告时间：10:30-12:00 am, Monday, OCT 9th, 2017
报告地点： Lecture Hall C302,New Science Building
报告摘要：MeV-ultrafast electron diffraction (MeV-UED), taking advantage of its high-sensitivity to phonons and the large interaction cross-sections of electrons with matter, has been identified as one of the frontiers and future directions of modern electron microscopy. It enables us to reveal competing orders of electrons and phonons as well as hidden states far-from equilibrium to address some key issues in condensed matter physics. In this presentation, I will give two examples of our recent studies. The first is on observations of strong electron-lattice interaction and how to disentangle various phonon modes in charge/orbital ordered LaSr2Mn2O7manganite using time-resolved electron crystallography method we developed. The work provides direct evidence of polaron formation and transport as the key mechanism for the colossal magnetoresistance in the system. The second example is the study of electron and lattice dynamics of optimally doped Bi2Sr2CaCu2O8+ō. By quantitatively measuring the diffuse scattering after photoexcitation our work illustrates the preferential coupling of electrons to the in-plane Cu-O bond-stretching phonon. The observed unique electron-phonon interactions beyond the N-temperature model provide insight in resolving longstanding controversies surrounding equilibrium interactions in the high-Tcsuperconductor.
