Valley-dependent exciton fine structure and Autler-Townes doublets from Berry phases in monolayer MoSe2
Journal
Nature materials
Journal Volume
18
Journal Issue
10
Pages
1065
Date Issued
2019-10
Author(s)
Utama, M Iqbal Bakti
Ong, Chin Shen
Cao, Ting
Regan, Emma C
Horng, Jason
Shen, Yuxia
Cai, Hui
Watanabe, Kenji
Taniguchi, Takashi
Tongay, Sefaattin
Deng, Hui
Zettl, Alex
Louie, Steven G
Wang, Feng
Abstract
The Berry phase of Bloch states can have profound effects on electron dynamics1-3 and lead to novel transport phenomena, such as the anomalous Hall effect and the valley Hall effect4-6. Recently, it was predicted that the Berry phase effect can also modify the exciton states in transition metal dichalcogenide monolayers, and lift the energy degeneracy of exciton states with opposite angular momentum through an effective valley-orbital coupling1,7-11. Here, we report the observation and control of the Berry phase-induced splitting of the 2p exciton states in monolayer molybdenum diselenide (MoSe2) using the intraexciton optical Stark spectroscopy. We observe the time-reversal-symmetric analogue of the orbital Zeeman effect resulting from the valley-dependent Berry phase, which leads to energy difference of +14 (-14) meV between the 2p+ and 2p- exciton states in the K (K') valley, consistent with the ordering from our ab initio GW-Bethe-Salpeter equation results. In addition, we show that the light-matter coupling between intraexciton states is remarkably strong, leading to a prominent valley-dependent Autler-Townes doublet under resonant driving. Our study opens up pathways to coherently manipulate the quantum states and excitonic excitation with infrared radiation in two-dimensional semiconductors.
Subjects
QUASI-PARTICLE; POLARIZATION
SDGs
Publisher
NATURE PUBLISHING GROUP
Type
journal article