Physical Chemistry Seminar: Professor Xiaoyang Zhu, Columbia University

Physical Chemistry Seminar: Professor Xiaoyang Zhu, Columbia University
Date
Tue February 16th 2021, 4:00 - 5:00pm
Location
Zoom

Physical Chemistry Seminar: Professor Xiaoyang Zhu, Columbia University (Host: Fang Liu)

About the Seminar

"Controlling Excitons"

An exciton is a quasi-particle consisting of an electron and a hole bound by the Coulomb potential.  It is a solid and excited state analog of the hydrogen atom. Excitons are fundamental to semiconductors and determine a range of processes involving the conversion of light to charge or charge to light. As bosonic particles, many-body interaction of excitons can lead to quantum phases, e.g., Bose-Einstein condensates (BECs). Compared to their bulk counterparts, the exciton binding energy can be increased by order(s) of magnitude in low dimensional materials, such as zero-dimensional (0D) quantum dots (QDs) and two-dimensional (2D) quantum wells, a result of both spatial confinement and reduced dielectric screening of the electron-hole pair.  In this lecture, I will discuss recent efforts in my laboratory to control excitons. We explore a number of approaches, including i) the spatial separation of the charge neutral exciton in a 2D transition-metal dichalcogenide (TMDC) monolayer into dipolar and quadrupolar exciton in TMDC hetero-bilayers and trilayers; ii) the spatial localization of 2D delocalized interlayer exitons into ordered arrays of 0D QD-like potential traps formed by the moiré pattern in TMDC heterobilayers; iii) the switching on/off of interlayer electronic/excitonic hybridization by magnetic order in 2D magnetic semiconductor bilayers and multilayers; and iv) the hybridization of excitons with photons to form exciton-polaritons, particularly those of the photonic analog of spin-orbital coupling, that undergo condensation into BECs with spin textures. A major goal of these efforts is to realize quantum simulators based on excitons.

About the Speaker

Xiaoyang Zhu is the Howard Family Professor of Nanoscience at Columbia University. He received a BS degree from Fudan University in 1984, a PhD from the University of Texas at Austin in 1989, and did postdoctoral research with Gerhard Ertl at the Fritz-Haber-Institute. Before joining Columbia University in 2013, he served on the faculty at Southern Illinois University, the University of Minnesota, and the University of Texas at Austin. His honors include a Dreyfus New Faculty Award, a Cottrell Scholar Award, a Friedrich Wilhelm Bessel Award, an APS Fellowship, a Vannevar Bush Faculty Fellowship, and an ACS Ahmed Zewail Award. Among his professional activities, he served as director of the DOE Energy Frontier Research Center (EFRC), is serving as associate editors for Science Advances and Journal of Chemical Physics, and is a scientific advisor to the Fritz-Haber-Institute of the Max-Planck Society in Germany.