Exciton-exciton interaction in transition-metal dichalcogenide monolayers

Abstract

We study theoretically the Coulomb interaction between excitons in transition metal dichalcogenide (TMD) monolayers. We calculate direct and exchange interaction for both ground and excited states of excitons. The screening of the Coulomb interaction, specific to monolayer structures, leads to the unique behavior of the exciton-exciton scattering for excited states, characterized by the nonmonotonic dependence of the interaction as function of the transferred momentum. We find that the nontrivial screening enables the description of TMD exciton interaction strength by approximate formula which includes exciton binding parameters. The influence of screening and dielectric environment on the exciton-exciton interaction was studied, showing qualitatively different behavior for ground state and excited states of excitons. Furthermore, we consider exciton-electron interaction, which for the excited states is governed by the dominant attractive contribution of the exchange component, which increases with the excitation number. The results provide a quantitative description of the exciton-exciton and exciton-electron scattering in transition metal dichalcogenides, and are of interest for the design of perspective nonlinear optical devices based on TMD monolayers.

Highly nonlinear trion-polaritons in a monolayer semiconductor

“…To describe the observed neutral exciton-nonlinearity we developed a model taking into account the two-and three-exciton exchange processes 30,31 (see 'Methods' and Supplementary Note 2). At 3 × 10 3 < n tot < 3 × 10 4 μm −2 within an experimental error there is agreement between theory and experiment ( Fig.…”

Two-dimensional semiconductors in the regime of strong light-matter coupling

“…This interaction matrix element is given by , where E B ~ e 2 /( a B ) is the exciton binding energy evaluated in the hydrogenic model with the effective screening constant and C is a constant. scales with the excitonic Bohr radius 104 , 105 , which is rather small (on the order of 1 … 2 nm) in most TMDC materials. Despite somewhat weak dielectric screening in TMDC MLs, exciton–exciton interaction turns out to be less efficient as compared with III–V semiconductors (the expression for can be also recast via the reduced mass μ of the electron–hole pair as ~ ℏ 2 / μ .…”

Low-temperature annihilation rate for quasilocalized excitons in monolayer MoS2

“…momentum), or exchange. Though direct scattering has recently been theoretically analyzed [40], it is forestalled if both of the excitons are initially bright and in the ground states of their respective orbital ladders. This is because the scattering process must lower the energy of one exciton while increasing the energy of the other, and since both excitons are at the minimum possible energy level, neither can decrease in energy while still maintaining coherence.…”