Spatially indirect intervalley excitons in bilayer WSe2

Zhiheng Huang, Yanchong Zhao, Tao Bo, Yanbang Chu, Jinpeng Tian, Le Liu, Yalong Yuan, Fanfan Wu, Jiaojiao Zhao, Lede Xian, Kenji Watanabe, Takashi Taniguchi, Rong Yang, Dongxia Shi, Luojun Du, Zhipei Sun, Sheng Meng, Wei Yang, Guangyu Zhang

Research output: Contribution to journalArticleScientificpeer-review

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Spatially indirect excitons with displaced wave functions of electrons and holes play a pivotal role in a large portfolio of fascinating physical phenomena and emerging optoelectronic applications, such as valleytronics, exciton spin Hall effect, excitonic integrated circuit, and high-temperature superfluidity. Here, we uncover three types of spatially indirect excitons (including their phonon replicas) and their quantum-confined Stark effects in hexagonal boron nitride encapsulated bilayer WSe2 by performing electric field-tunable photoluminescence measurements. Because of different out-of-plane electric dipole moments, the energy order between the three types of spatially indirect excitons can be switched by a vertical electric field. Remarkably, we demonstrate, assisted by first-principles calculations, that the observed spatially indirect excitons in bilayer WSe2 are also momentum indirect, involving electrons and holes from Λ and K/Γ valleys in the Brillouin zone, respectively. This is in contrast to the previously reported spatially indirect excitons with electrons and holes localized in the same valley. Furthermore, we find that the spatially indirect intervalley excitons in bilayer WSe2 can exhibit considerable, doping-sensitive circular polarization. The spatially indirect excitons with momentum-dark nature and highly tunable circular polarization may provide a firm basis for the understanding and engineering of technological applications in photonics and optoelectronics.

Original languageEnglish
Article numberL041409
JournalPhysical Review B
Issue number4
Publication statusPublished - 15 Jan 2022
MoE publication typeA1 Journal article-refereed


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