Programme

P.16 -- Poster, VCTP-47

Date: Tuesday, 2 August 2022

Time: 08:30 - 10:00

Exciton behaviors in monolayer WSe_2 under isotropic strain

Tran Thi Nhan (1), Luong Thi Theu (2), Tran Quang Huy (3), Phung Viet Bac (2), Van An Dinh (4)

(1) Faculty of Fundamental Sciences, Hanoi University of Industry, 298 Cau Dien, Hanoi, Vietnam. (2) VNU Vietnam Japan University, Luu Huu Phuoc, My Dinh I, Hanoi, Vietnam. (3) Faculty of Physics, Hanoi Pedagogical University 2, Hanoi, Vietnam. (4) Department of Precision Engineering, Graduate School of Engineering, Osaka University, Japan.

We present a density functionals study of the exciton behaviors under isotropic strain in monolayer WSe_2. Firstly, the formation of optical and momentum excitons is explored by analyzing the spin projected band structure of the strainless material. Then, the essential effects such as the reduction of the bandgap and the change in the dispersion degree of the energy extrema near the gap caused by strain are revealed. We found that the modification in the electronic structure due to the tensile strain enhances the direct transitions and hinders indirect transitions of electrons from the valence band to the conduction band. Therefore, tensile may lead to an additional appearance of optical excitons and a disappearance of momentum excitons. The change of the electronic structure caused by the compression enhances the indirect transitions and counteracts direct transitions, resulting in the additional appearance of the momentum excitons and disappearance of optical excitons. These findings can provide a possible path to manipulate the excitons in monolayer transition metal dichalcogenide materials upon isotropic strain.

Presenter: Tran Thị Nhan