Optical Response of Excitons Interacting with Electronic Wigner Crystals in Two-Dimensional Materials

It is anticipated that Wigner crystal (WC) formation can occur in two-dimensional (2D) materials with low-density free carriers. Recent optical measurements suggest that Umklapp signals of exciton scattering from the WC lattice can be detected [1]. In this study, we perform density functional theory (DFT) calculations [2] to investigate the charge distribution of WC carriers in monolayer transition-metal dichalcogenides (TMDCs) and the coupling between excitons and the polarization of WC charges. We explore the electronic structure of exciton polarons in the presence of a Wigner crystal within the effective-mass approximation, considering both the ideal 2D Coulomb potential and the Keldysh model potential [3] for inter-particle interactions. Theoretical predictions of the energy dispersion of exciton-polaron states, including low-lying excited states, in the presence of the Wigner crystal will be presented. Additionally, we will discuss the optical signature arising from Umklapp scattering of exciton-polarons interacting within the Wigner crystal. 

 

[1] T. Smoleński et al., Nature 595,  53 (2021)

[2] M. Zarenia, D. Neilson, B. Partoens, F. M. Peeters, Phys. Rev. B 95, 115438 (2017)

[3] L. Keldysh, JETP Lett. 29, 658 (1979).