报告题目: Polaritons in two-dimensional semiconductors
报告人：Dr. Xiaoze Liu（武汉大学物理科学与技术学院）
The “marriage” of light and matter in solid-state systems leads to the formation of hybrid quasiparticles called polaritons with unprecedented physical properties. This leads to the booming research field of nano-optics and striking discoveries of quantum optics, such as Bose-Einstein condensation­ and photon blockade. Of various polariton species, exciton polaritons have been one of the most intriguing and the most studied polaritons for their profound quantum nature. The research of exciton polaritons have been evolving into a new era with the emergent two-dimensional (2D) semiconductors for their tremendous potential in practical quantum applications. 2D semiconductors, i.e., transition metal dichalcogenides (TMD) monolayers and heterostructures, exhibit outstanding excitonic properties to break the limitations of conventional quantum well systems. In the last few years since the realization of exciton polaritons at room temperature1, TMD monolayers with large exitonic binding energies demonstrate the robustness and tunability of the coherent light-matter coupling in exciton-polaritons from low temperature throughout room temperature2. Moreover, 2D exciton polaritons in TMD monolayers also show unexplored nonlinear optics with quite distinct quantum electrodynamics based on valley excitonic physics, which has been hardly shown in other polaritonic systems3. Furthermore, 2D exciton polaritons could also lead to nonlinear valley phonon scattering4. In a plasmonic cavity strongly coupled with a TMD monolayer, the phonon scattering is equipped with valley degree of freedom and boosted with superlinear enhancement to a stimulated regime, as revealed by Raman spectroscopy and a theoretical model4. The valley polarization is drastically enhanced and sustained throughout the stimulated regime, suggesting a coherent scattering process enabled by exciton polaritons. This talk would start as a general perspective to get an overlook of the polariton research, and hopefully stimulate students’ interests into some cutting-edge research, which looks “obscure and distant” but is actually quite inspiring and dynamic.
Dr. Xiaoze Liu is currently a professor of Physics in Wuhan University, School of Physics and Technology. After he obtained his PhD degree in Prof. Vinod Menon’s group from City University of New York, he became a postdoctoral scholar (2015-2019) in Professor Xiang Zhang’s group in NSF Nanoscale Science and Engineering Center, University of California, Berkeley. In October 2019, he joined Wuhan University and his current research focuses on the cavity quantum dynamics and photonic applications based on the coupling between photons and low-dimensional semiconductors in artificial microstructures. Some of the research results have been recently published in scientific journals such as Nature Materials, Nature Photonics, Phys. Rev. Lett., PNAS, Nano Lett., etc.