Seminar & Colloquium
[세미나: 7월 19일(금), 오전 11시] Dr. Woncheol Lee, University of California, Santa Barbara
Title
Phonon screening of excitons in atomically thin nitrides
Speaker
Dr. Woncheol Lee, Materials Department, University of California, Santa Barbara, CA, USA
* Education
- 2017 - 2023 Ph.D. in Department of Electrical and Computer Engineering, University of Michigan, MI, USA
Advisor: Prof. Emmanouil Kioupakis / Mackillo Kira
- 2015 - 2017 M.S. in Department of Electrical and Computer Engineering, Seoul National University
Advisor: Prof. Young June Park
- 2008 - 2015 B.S. in Department of Electrical and Computer Engineering, Seoul National University,
Minor: Department of Materials Science and Engineering
* Professional Experience
- 2023 - 2024 Post-doctoral Researcher, University of Santa Barbara, CA, USA
Advisor: Prof. Chris Van de Walle
- 2023 Pre-doctoral Researcher, Center for Computational Quantum Physics (CCQ), Flatiron Institute, NY, USA
Advisor: Prof. Cyrus Dreyer
- 2017 - 2023 Graduate Student Research Assistant (GSRA), University of Michigan, MI, USA
| Date | Friday, July 19th , 2024
| Time | 11:00 ~
| Venue | 33동 125호(WCU 다목적실)
[Abstract]
Atomically thin semiconductors, encompassing both 2D materials and quantum wells, exhibit a pronounced enhancement of excitonic effects due to geometric confinement. Consequently, these materials have become foundational platforms for the exploration and utilization of excitons. Recent ab initio studies have demonstrated that phonons can substantially screen electron-hole interactions in bulk semiconductors and strongly modify the properties of excitons. While excitonic properties of atomically thin semiconductors have been the subject of extensive theoretical investigations, the role of phonon screening on excitons in atomically thin structures remains unexplored. In this work, we demonstrate via ab initio GW-Bethe-Salpeter equation calculations that phonon screening can have a significant impact on optical excitations in atomically thin semiconductors. We further show that the degree of phonon screening can be tuned by structural engineering. We focus on atomically thin GaN quantum wells embedded in AlN and identify specific phonons in the surrounding material, AlN, that dramatically alter the lowest-lying exciton in monolayer GaN via screening. Our studies provide new intuition beyond standard models into the interplay among structural properties, phonon characteristics, and exciton properties in atomically thin semiconductors, and have implications for future experiments.
| Host | 손준우 교수(02-880-7195)