title: Valley and band structure engineering of folded MoS(2) bilayers.
abstract: Artificial structures made of stacked two-dimensional crystals have recently been the focus of intense research activity. As in twisted or stacked graphene layers, these structures can show unusual behaviours and new phenomena. Among the various layered compounds that can be exfoliated, transition-metal dichalcogenides exhibit interesting properties governed by their structural symmetry and interlayer coupling, which are highly susceptible to stacking. Here, we obtain-by folding exfoliated MoS2 monolayers-MoS2 bilayers with different stacking orders, as monitored by second harmonic generation and photoluminescence. Appropriate folding can break the inversion symmetry and suppress interlayer hopping, evoking strong valley and spin polarizations that are not achieved in natural MoS2 bilayers of Bernal stacking. It can also enlarge the indirect bandgap by more than 100 meV through a decrease in the interlayer coupling. Our work provides an effective and versatile means to engineer transition-metal dichalcogenide materials with desirable electronic and optical properties.
authors.affiliation: 1] State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China [2] Key Laboratory of Micro and Nano Photonic Structures (MOE), Fudan University, Shanghai 200433, China.
authors.forename: Tao
authors.initials: T
authors.lastname: Jiang
authors.affiliation: 1] State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China [2] Key Laboratory of Computational Physical Sciences (MOE), Fudan University, Shanghai 200433, China.
authors.forename: Hengrui
authors.initials: H
authors.lastname: Liu
authors.affiliation: 1] State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China [2] Key Laboratory of Micro and Nano Photonic Structures (MOE), Fudan University, Shanghai 200433, China.
authors.forename: Di
authors.initials: D
authors.lastname: Huang
authors.affiliation: 1] State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China [2] Key Laboratory of Micro and Nano Photonic Structures (MOE), Fudan University, Shanghai 200433, China.
authors.forename: Shuai
authors.initials: S
authors.lastname: Zhang
authors.affiliation: 1] State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China [2] Key Laboratory of Micro and Nano Photonic Structures (MOE), Fudan University, Shanghai 200433, China.
authors.forename: Yingguo
authors.initials: Y
authors.lastname: Li
authors.affiliation: 1] State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China [2] Key Laboratory of Computational Physical Sciences (MOE), Fudan University, Shanghai 200433, China [3] Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093, China.
authors.forename: Xingao
authors.initials: X
authors.lastname: Gong
authors.affiliation: 1] State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China [2] Key Laboratory of Micro and Nano Photonic Structures (MOE), Fudan University, Shanghai 200433, China [3] Physics Department, University of California at Berkeley, Berkeley, California 94720-7300, USA.
authors.forename: Yuen-Ron
authors.initials: YR
authors.lastname: Shen
authors.affiliation: 1] State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China [2] Key Laboratory of Micro and Nano Photonic Structures (MOE), Fudan University, Shanghai 200433, China [3] Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093, China.
authors.forename: Wei-Tao
authors.initials: WT
authors.lastname: Liu
authors.affiliation: 1] State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China [2] Key Laboratory of Micro and Nano Photonic Structures (MOE), Fudan University, Shanghai 200433, China [3] Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093, China.
authors.forename: Shiwei
authors.initials: S
authors.lastname: Wu