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Higher-Order Correlated Entities in 2D Semiconductors

Speaker Prof. Cun-Zheng NING
Affiliation College of Integrated Circuits and Optoelectronic Chips, Shenzhen Tech University, China
Date May 16, 2024 (Thursday)
Time 2:30 p.m.
Venue Room 522, 5/F, Chong Yuet Ming Physics Building, The University of Hong Kong


Quasi particles such as excitons, trions, and bi-excitons are important both for the understanding of fundamental physics in semiconductors and for photonic applications. Such quasi-particles in 2D monolayer semiconductors have attracted a great deal of attention in recent years due to their many unique properties. In this talk, we will present examples of our recent results on the optical study of 2D materials, especially possible new higher-order correlated entities beyond those well-known ones. For the case of three-particle interaction, we will show that the common concept of a trion needs to be re-examined and there are two possible configurations due to the Coulomb interaction. Our focus will be on the recent experimental observation of a series of new spectral features that are not attributable to excitons, trions, or bi-excitons. Our combined theory and experiments provide strong evidence for the existence of a new four-particle entity, the quadruplon which corresponds to an irreducible cluster of fourth order with two electrons and two holes. Details of theory and experimental evidence will be discussed.



Cun-Zheng Ning is a Chair Professor and Dean of the College of Integrated Circuits and Optoelectronic Chips (ICOC) at Shenzhen Technology University and an Adjunct Professor of Electronic Engineering at Tsinghua University. He was a professor of electrical engineering and an affiliate professor in physics and materials science and engineering at Arizona State University from 2006 to 2021. He received his Ph.D. in physics from the University of Stuttgart, Germany, followed by a postdoc at the University of Arizona. He was a senior scientist, nanophotonics group leader, and nanotechnology task manager at NASA Ames Research Centre (1997-2007), ISSP Visiting Professor at the University of Tokyo (2006), Visiting Professor at Technical University of Berlin and Tsinghua University (2013). His group was one of the first to demonstrate a plasmonic nanolaser, which was considered by the MIT Technology Review as “the first to overcome the wavelength constraints on the size of lasers”. He invented and demonstrated the first white lasers which won the Top Ten Engineering Inventions of the Year from the US Magazine Popular Science. He was a winner of several awards including NASA and NASA Contractor Awards, NASA Space Act Patent Awards, CSC Technical Excellence Award, IEEE/Photonics Society Distinguished Lecturer Award, and the Alexander von Humboldt Research Award. Dr. Ning is a Fellow of the Optical Society (OSA), IEEE, and the Electromagnetic Academy.


Anyone interested is welcome to attend.