Ultrafast nano-imaging – probing structure, coupling, and dynamics of matter on its natural length and time scales

Guest Speaker： Prof. Markus Raschke, University of Colorado at Boulder., USA

Inviter: Prof. Qing Dai

Date&Time: Thursday, 11 December, 10:30-11:30

Venue:  Yiucheng Lecture Hall (500), Xu Zuyao Building

Biography:

Markus Raschke is professor at the Department of Physics and JILA at the University of Colorado at Boulder. His research is on the development and application of nano-scale nonlinear and ultrafast spectroscopy to control the light-matter interaction on the nanoscale. These techniques allow for imaging structure and dynamics of molecular and quantum matter with nanometer spatial resolution. He received his PhD in 2000 from the Max-Planck Institute of Quantum Optics and the Technical University in Munich, Germany. Following a postdoc at the University of California at Berkeley, and research group leader at the Max-Born-Institute in Berlin, he became faculty member at the University of Washington in 2006, before moving to the University of Colorado and JILA in 2010. He is fellow of the Optical Society of America, the American Physical Society, the American Association for the Advancement of Science, and the Explorers Club.

Abstract:

Understanding and ultimately controlling the properties of matter, from molecular to quantum systems, requires imaging their elementary excitations on their natural time and length scales of femtoseconds and nanometers. In order to achieve this goal, we developed scanning probe microscopy with ultrafast and shaped laser pulses for multiscale spatio-temporal optical nano-imaging. In corresponding ultrafast movies, we resolve the fundamental quantum dynamics from the fastest few-femtosecond coherent to the nanosecond thermal transport regime.

I will discuss specific examples visualizing in space and time the nanoscale heterogeneity of electronic and structural processes in different classes of functional materials. Specifically, in coherent nonlinear nanoimaging of graphene and 2D semiconductors, we resolve the competing dynamics of intra- and interlayer coupling underlying the mechanisms of the emergent quantum phenomena in 2D heterostructures [1,2]. In the extension to far-from equilibrium excitation with even simultaneous spatial, spectral, and temporal resolution we resolve electron-phonon, cation-lattice, and coupled polaron dynamics in photovoltaic perovskites obtaining a real-space and real-time view of their complex photophysical response [3,4]. Lastly, we advanced nano-imaging also into the strong field, Purcell-enhanced, and strongly-coupled QED regime, with coherent superposition states for novel quantum-enhanced sensing and imaging [5,6]. Probing directly in the local electronic and molecular environments this will inform on the most fundamental level what limits coherence in solid-state quantum systems. I will then close with a perspective towards the ultimate goal of imaging and control, to systematically link coupled internal degrees of freedom to overcome relaxation and dissipation towards quantum materials with desired macroscopic performance.