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Title: Valley-dependent exciton fine structure and Autler–Townes doublets from Berry phases in monolayer MoSe2

Abstract

The Berry phase of Bloch states can have profound effects on electron dynamics and lead to novel transport phenomena, such as the anomalous Hall effect and the valley Hall effect. 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 coupling. 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. Finally, our study opens up pathways to coherently manipulate the quantum states and excitonic excitation with infrared radiation in two-dimensional semiconductors.

Authors:
ORCiD logo [1]; ORCiD logo [2]; ORCiD logo [2]; ORCiD logo [2];  [2];  [3];  [4];  [5]; ORCiD logo [6];  [6];  [4]; ORCiD logo [3]; ORCiD logo [7]; ORCiD logo [2]; ORCiD logo [7]
  1. Univ. of California, Berkeley, CA (United States)
  2. Univ. of California, Berkeley, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
  3. Univ. of Michigan, Ann Arbor, MI (United States)
  4. Arizona State Univ., Tempe, AZ (United States)
  5. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Center for Nanophase Materials Science (CNMS)
  6. National Inst. for Materials Science, Tsukuba (Japan)
  7. Univ. of California, Berkeley, CA (United States). Kavli Energy NanoScience Inst.; Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Publication Date:
Research Org.:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Materials Sciences & Engineering Division; USDOD; National Science Foundation (NSF); US Army Research Office (ARO)
OSTI Identifier:
1605255
Grant/Contract Number:  
AC02-05CH11231; ACI-1548562
Resource Type:
Accepted Manuscript
Journal Name:
Nature Materials
Additional Journal Information:
Journal Volume: 18; Journal Issue: 10; Journal ID: ISSN 1476-1122
Publisher:
Springer Nature - Nature Publishing Group
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE

Citation Formats

Yong, Chaw-Keong, 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., and Wang, Feng. Valley-dependent exciton fine structure and Autler–Townes doublets from Berry phases in monolayer MoSe2. United States: N. p., 2019. Web. https://doi.org/10.1038/s41563-019-0447-8.
Yong, Chaw-Keong, 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. Valley-dependent exciton fine structure and Autler–Townes doublets from Berry phases in monolayer MoSe2. United States. https://doi.org/10.1038/s41563-019-0447-8
Yong, Chaw-Keong, 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., and Wang, Feng. Mon . "Valley-dependent exciton fine structure and Autler–Townes doublets from Berry phases in monolayer MoSe2". United States. https://doi.org/10.1038/s41563-019-0447-8. https://www.osti.gov/servlets/purl/1605255.
@article{osti_1605255,
title = {Valley-dependent exciton fine structure and Autler–Townes doublets from Berry phases in monolayer MoSe2},
author = {Yong, Chaw-Keong and Utama, M. Iqbal Bakti and Ong, Chin Shen and Cao, Ting and Regan, Emma C. and Horng, Jason and Shen, Yuxia and Cai, Hui and Watanabe, Kenji and Taniguchi, Takashi and Tongay, Sefaattin and Deng, Hui and Zettl, Alex and Louie, Steven G. and Wang, Feng},
abstractNote = {The Berry phase of Bloch states can have profound effects on electron dynamics and lead to novel transport phenomena, such as the anomalous Hall effect and the valley Hall effect. 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 coupling. 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. Finally, our study opens up pathways to coherently manipulate the quantum states and excitonic excitation with infrared radiation in two-dimensional semiconductors.},
doi = {10.1038/s41563-019-0447-8},
journal = {Nature Materials},
number = 10,
volume = 18,
place = {United States},
year = {2019},
month = {8}
}

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Figures / Tables:

Fig. 1 Fig. 1: Schematics of exciton spectrum and optical transition in MoSe2 monolayer. a. Illustration of the optical transition and selection rules for one-photon and two-photon excitations in the K and K’ valleys of MoSe2 monolayer. |𝑔⟩ , |1𝑠⟩, |2𝑝⟩, and |2𝑝+⟩ denote the ground state, 1𝑠, 2𝑝, and 2𝑝+-exciton states,more » respectively. The symbol 𝜎+ and 𝜎 denotes left and right circular polarization state, respectively. b. Optical micrograph of monolayer MoSe2 encapsulated by hBN layers on alumina coated silver substrate. The scale bar corresponds to 50 𝜇m. c. The reflection contrast of hBN encapsulated MoSe2 monolayer on alumina coated silver surface at 77 K. It shows prominent A-exciton resonance at 1.627 eV with a FWHM of ≈9 meV. d. Schematic diagram illustrating the avoided-crossing behavior due to quantum-mechanical coupling between the infrared photons field and the 1s-2p+ electronic transition. The dashed lines show the unperturbed |1𝑠, 𝑛ℏ𝜔⟩ and the |2𝑝+, (𝑛 − 1)ℏ𝜔⟩ states as a function of the pump photon energy, and the blue and red solid lines show the dressed exciton states from quantum hybridization. The arrows show the optical transitions from the ground state to the dressed 1s exciton state.« less

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      Figures/Tables have been extracted from DOE-funded journal article accepted manuscripts.