题 目：Nonlinear Optics of Condensed Phases: From Equilibrium Structure to Non-equilibrium Dynamics
报告人：John A. McGuire，美国密歇根州立大学
时 间：5月5日（周五 ），上午9:00-10:00
The central questions in condensed matter physics concern the electronic structure and symmetries of systems at equilibrium, fluctuations of equilibrium systems, and relaxation of non-equilibrium states. I will describe our investigations of these questions in low-dimensional and interfacial systems via ultrafast and nonlinear optical techniques. Examples will include the change of electronic structure in atomically thin layered GaSe and the electronic structure of biexcitons in graphene quantum dots. More attention will be given to the dynamics of the hydrogen-bond network of water at an interface with a hydrophobic surface[3,4]. What makes water special is its strong, highly dynamics hydrogen-bond network, but this network is terminated at an interface. This leads to different properties of the interface compared to the bulk. We can probe these differences by using sum-frequency generation as a surface-sensitive probe after infrared excitation of the dangling OH stretch mode of interfacial water. The evolution of this dangling mode is dominated by reorientation to a hydrogen-bonded configuration, which we monitor by time- and polarization-resolved sum-frequency generation. I will conclude with a discussion of nonlinear optical approaches to studying exciton interactions in layered systems and novel orders in correlated and topological systems.
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 C. Sun et al., Nano Lett. 15, 5472 (2015).
 C. Sun et al., Phys. Rev. Lett. 113, 107401 (2014).
 S.H. Xiao et al. J. Amer. Chem. Soc. 138, 5551 (2016).
John McGuire: Assistant Professor, Michigan State University, U.S.A. 2009.08 - present
Ph.D. from University of California, Berkeley 2004.12
Postdoctoral Fellow, University of California, Berkeley 2005
Postdoctoral Research Associate, Los Alamos National Laboratory, U.S.A. 2006.02-2009.08
Research fields: time-resolved and nonlinear optical studies of low-dimensional systems (layered materials and quantum dots) and interfaces.