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Controlling the electronic state of two-layer molybdenum disulfide in an "origami" manner

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Author : Jenny Ruan
Update time : 2019-06-24 14:23:22
Transition metal dichalcogenide is one of the most important two-dimensional quantum functional materials in the world in recent years. They have a honeycomb structure similar to graphene, but adjacent lattice points are alternately occupied by different atoms, and have strong spin-orbit coupling, thus exhibiting a series of novel physical properties. Taking molybdenum disulfide as an example, from the multilayer to the monoatomic layer, the energy band structure of molybdenum disulfide evolved from an indirect band gap to a direct band gap, which greatly improved the fluorescence efficiency and the light absorption cross section; Molybdenum sulfide has a new electronic state, the energy quantum state, which can be regarded as the third internal degree of freedom of electrons after charge and spin. Deep understanding of the intrinsic mechanisms of these novel quantum phenomena to further realize their manipulation is of great value to the field of condensed matter physics, and to the future of new electronics and optoelectronics.

According to Professor Wu Shiwei, the idea of ​​this work is based on the "ultra-thin" nature of two-dimensional quantum functional materials: that the monoatomic layer material is folded directly like a piece of paper, developing a double that cannot be obtained by natural crystallization or epitaxial growth. Layer structure. Depending on the direction of folding and the position of the fold line, molybdenum disulfide "origami" has a rich variety of interlayer arrangements, which in turn leads to different macrostructure symmetry and interlayer coupling. The research team used various experimental techniques such as nonlinear second harmonic imaging, fluorescence spectroscopy, and optical depolarization, combined with first-principles calculations, to study the spatial and electronic structures of various types of molybdenum disulfide "origami".
Studies have shown that the natural molybdenum disulfide double layer with central inversion symmetry has only weak energy valley-spin polarization, while the molybdenum disulfide "origami" can directly break the central inversion symmetry, which in turn greatly enhances this polarization. In addition, the change of interlayer coupling can not only greatly affect the indirect band gap of molybdenum disulfide "origami", but also can be used as a "switch" in the relationship between the spine and electron spin in "folding paper".The symmetric symmetrical molybdenum disulfide "origami" also retains a strong spin polarization. This work provides a rich experimental platform for understanding and manipulating the interaction and effects of multiple degrees of freedom such as valley, spin, and interlayer coupling, and provides a way to prepare two-dimensional artificial materials and future new quantum devices.
Luoyang Trunnano Tech Co., Ltd (TRUNNANO) is a professional molybdenum disulfide manufacturer with over 12 years experience in chemical products research and development. If you are looking for high quality molybdenum disulfide, please feel free to contact us and send an inquiry.

 
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