Programme

P.50 -- Poster, VCTP-44

Date: Tuesday, 30 July 2019

Time: 08:30 - 10:00

Retrieval of structural parameters of monolayer transition-metal dichalcogenides from the exciton energy spectrum

Duy-Nhat Ly (1), Thanh-Truc N. Huynh (2), Ngoc-Hung Phan (1), Van-Hoang Le (1)

(1) Ho Chi Minh City University of Education, Ho Chi Minh City, Vietnam (2) Marie Curie High School, Ho Chi Minh City, Vietnam

Exciton energy spectra of two-dimensional systems such as graphene, monolayer transition-metal dichalcogenides (TMD) have been investigated actively in the last few years (see, for example [1] and cited therein). It has been found that the interaction between the hole and electron forming an exciton is not Coulombic but instead screened by the reduced dimensionality. This screening potential is well described by Keldysh model [2] which contains some structural parameters such as the exciton effective mass and the screening length related to the polarizability of materials. This report is about an idea of determining the structural parameters from the experimental exciton energy spectrum. Theoretical exciton energies calculated within the Keldysh model by different parameters are compared with the experimental data, and the best fit gives the right structural parameters of the materials. We have applied this idea to very recent experimental data of a monolayer TMD WSe2 sandwiched by two hBN slabs [1] and published the first results in [3]. Furthermore, we analyze the predicted sizes of the exciton with some excited states and compare them with the experimental data. Finally, we apply the approach for other monolayer TMDs such as MoS2, MoSe2, WS2, and WSe2 whose experimental exciton energies are available recently. [1] A. V. Stier, N. P. Wilson, K. A. Velizhanin, J. Kono, X. Xu, S. A. Crooker, Magnetooptics of exciton Rydberg states in a monolayer semiconductor, Phys. Rev. Lett. 120 (2018) 057405. [2] L. V. Keldysh, Coulomb interaction in thin semiconductor and semimetal films, JETP Lett. 29 (1979) 658-660. [3] Duy-Anh P. Nguyen, Duy-Nhat Ly, Dai-Nam Le, Ngoc-Tram D. Hoang, and Van-Hoang. Le, High-accuracy energy spectra of a two-dimensional exciton screened by reduced dimensionality with the presence of a constant magnetic field, Physica E 113 (2019) 152–164.

Presenter: Ly Duy-Nhat