Electronic band structure, valley excitons and optical properties of layered transition-metal dichalcogenides – Fanyao Qu – University of Brasilia (Presencial)

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Date(s) - 19/05/2022
17:00 - 18:00

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COLÓQUIO DO DEPARTAMENTO DE FÍSICA

Electronic band structure, valley excitons and optical properties of layered transition-metal dichalcogenides

Fanyao Qu – Institute of Physics, University of Brasilia

19 de maio – 5a. feira -17h – sala 776L

 

The discovery of two-dimensional (2D) materials has provided new opportunities for numerous research fields, including spintronics and valleytronics. The breakthrough of 2D materials was discovery of graphene in 2004. After that, many other 2D materials have been successfully synthesized. They are composed of single-element 2D materials, such as monolayer black phosphorus, monolayer arsenic, antimony, bismuth, silicene, germanene, stanene, borophene, etc., and of 2D binary compounds, such as metal oxides, transition-metal dichalcogenides (TMDCs), metal oxy/hydroxide borides.

Layered van der Waals materials (vdWs) such as TMDCs have shown strong variations of their properties as they are thinned to a single molecular layer. These include: (1) transitions from an indirect to a direct bandgap material, opening new opportunities for optoelectronic applications; (2) Enhanced many-body effect, such as, charge density wave, room temperature multi-exciton emissions or superconducting transitions; and (3) field tunability of many-body states. Besides these intriguing properties, two or more different 2D materials via weak vdW interactions can form van der Waals heterostructures that exhibit novel properties or enabling new device architectures.

In this talk, firstly, I will present our computational packet–WanTiBEXOS. It was developed in collaboration with Juarez L. F. Da Silva´s group in Chemistry Institute of University of Sao Paulo, São Carlos. Based on the output of first principle calculations, this packet can provide reliable optical properties for conventional semiconductors, 2D materials including 2D magnetic materials, vdW heterostructures and perovskite, etc. [1-5]. After that, I am going to focus on magnetic proximity effect on optical property of monolayer TMDCs deposited on a ferromagnetic insulating substrate [6]. Finally, I will show our recent results about electronic structures and optical properties of the TMD vdWs heterostructures, concentrating on interlayer excitons.

  1. Fanyao Qu, et. al. 2D Materials, 6, 045014 (2019).
  2. Jorlandio Francisco Felix, Arlon Fernandes da Silva, Sebastião Willam da Silva, Fanyao Qu, et. al., Nanoscale Horiz., 5, 259-267 (2020).
  3. Helena Bragança, Railson Vasconcelos, Jiyong Fu, Rennan Pinheiro D’Azevedo, Diego Rabelo da Costa, A. L. A. Fonseca, and Fanyao Qu, Rev. B, 100, 115306 (2019).
  4. Jiyong Fu,Junio M. R. Cruz, and Fanyao Qu, Phys. Lett. 115, 082101 (2019).
  5. C. Dias, Helena Bragança, Hao Zeng, A. L. A. Fonseca, De-Sheng Liu, and Fanyao Qu, Phys. Rev. B 101, 085406 (2020).
  6. Xiuwen Zhao, Fujun Liu, Junfeng Ren, and Fanyao Qu, Phys. Rev. B 104, 085119 (2021).  

http://www.fis.puc-rio.br/