2022/08/04(Thu)
11:00 -12:30
五樓第一會議室 5F, 1st Meeting Room
視訊演講 Video Seminar [ Meeting Link / ID: 2510 214 0662 / Password: 123456 ]
- 實體與視訊演講同時進行。
- Both physical seminar and virtual seminar are available.
Title
Light-matter interactions in atomically-thin transition metal dichalcogenides
Speaker
楊超強助理教授 (國立臺灣大學物理學系) Asst. Prof. Chaw-Keong Yong (Department of Physics, National Taiwan University)Abstract
Atomically thin transition metal dichalcogenides (TMDs) layered materials exhibit fascinating quantum phenomena and strong light-matter interactions owing to their unique electronic structure, reduced dimensionality, and prominent many-body interactions. The broken inversion symmetry gives rise to a pair of inequivalent degenerate band edge at the K and K’ valleys, which are coupled by the time-reversal symmetry. The finite Berry curvatures in each valley not only gives rise to the well-known valley Hall effects but also play a crucial role in defining the optical transition, which can be exploited to achieve all-optical control of valley pseudospin degree of freedom. However, probing the many-body interactions and the roles of Berry curvatures in defining the collective excitation in atomically thin 2D materials are rather challenging and usually complicated by various incoherent scattering processes. In this seminar, I will demonstrate our efforts in developing and employing ultrafast nonlinear spectroscopy [1-5] in exploring the light-matter interaction and emerging physical properties buried at the atomic interface of 2D heterostructures. I will first discuss with you the crucial roles of many-body interactions [1] and Berry curvatures [2] in defining the optical transition in atomically thin materials through quantum nonlinear optical probing methods. With that, I will demonstrate the principle of all-optical manipulation of the quantum states of matters and valley degree of freedoms using light at the femtosecond time scale [1-2]. Next, by developing few-cycle THz pulses, twisting the orbital overlap at the atomic interface of 2D heterostructure, we engineer the electron wavefunction, and demonstrate the large tuneability of Coulomb correlation, ultrafast exciton dynamics [3], as well as the emergence of rich polaron bands [4], for the first time. The abilities to access the electronic processes stroboscopically and manipulate the quantum states of matter through the extremely large optical fields have opened up new opportunities to explore the electron dynamics, quantum phase transition and coherent controls of quantum states of matter in the 2D flatlands.
1. Nature Physics, vol. 14, pp. 1092, 2018
2. Nature Materials, vol. 18, pp. 1065, 2019
3. Nature Communication, vol. 11, pp. 2167, 2020
4. Nature Communication, vol. 12, pp. 1719, 2021
5. Nature Communication, vol. 8, pp. 15953, 2017
Abstract
Language
演講語言 (Language): in English