[Distinguished Lecture Series]

Oct. 30^th Wed. 2019, 4:30pm
N Center #86120, Sungkyunkwan University, Suwon

Ultrafast optical studies of valley states in 2D transition metal dichalcogenides

Prof. Jonghwan Kim

(Department of Materials Science and Engineering & Department of Physics, POSTECH)

Abstract

Valley pseudospin of electron in a solid has emerged as a novel internal degree of freedom which arises from degenerate states at different positions in momentum space. Atomically thin transition metal dichalcogenides (TMD) has attracted particular interest because its unique spin-valley locked electronic structure can protect information carried by valley pseudospin. In this seminar, I will present our ultrafast optical studies on valley pseudospin dynamics of exciton and charge carriers in monolayer and heterostructure of TMD. Pure spin/valley diffusion current is generated with an optical pulse in TMD heterostructures where remarkably long lifetime (~20 μsec) and diffusion length (~20 μm) are observed. Ultrafast optical microscopy further reveals that the diffusion current can be effectively controlled by electrostatic doping. Our study shows that versatile control and robust valley pseudospin in atomically thin TMD opens up exciting new opportunities in information science and optoelectronic device applications.

Brief Bio

Jonghwan Kim, Ph. D., is interested in novel quantum phenomena emerging in low-dimension nanomaterials for fascinating optical science and optoelectronics. He has obtained Ph.D. in Physics at UC Berkeley in 2015 with the focus on ultrafast optical spectroscopy/microscopy, high quality 2D material preparation and nano-device fabrication. In POSTECH, as an assistant professor started from 2017, he has been constructing an interdisciplinary research team at the department of materials science and engineering to connect the bridge between fundamental physics and advanced material engineering.