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
地　点：同济大学物理馆512会议室

报告摘要：

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[1] and the electronic structure of biexcitons in graphene quantum dots[2]. 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.

[1] Y.H. Tang, et al., Phys. Rev. B 94, 125302 (2016).

[2] C. Sun et al., Nano Lett. 15, 5472 (2015).

[3] C. Sun et al., Phys. Rev. Lett. 113, 107401 (2014).

[4] S.H. Xiao et al. J. Amer. Chem. Soc. 138, 5551 (2016).

个人简介：

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.