Abstract
We report a combined theoretical/experimental study of dynamic screening of excitons in media with frequency-dependent dielectric functions. We develop an analytical model showing that interparticle interactions in an exciton are screened in the range of frequencies from zero to the characteristic binding energy depending on the symmetries and transition energies of that exciton. The problem of the dynamic screening is then reduced to simply solving the Schrodinger equation with an effectively frequency-independent potential. Quantitative predictions of the model are experimentally verified using a test system: neutral, charged and defect-bound excitons in two-dimensional monolayer WS2, screened by metallic, liquid, and semiconducting environments. The screening-induced shifts of the excitonic peaks in photoluminescence spectra are in good agreement with our model.
Highlights
We report a combined theoretical/experimental study of dynamic screening of excitons in media with frequency-dependent dielectric functions
Further we show that even in the case of dynamic screening, Excitonic complexes (EC) binding energies can still be calculated using effectively static dielectric functions and screened interaction potentials evaluated at a certain fixed effective frequency that depends on EC symmetries
We rely on the on the experiments by Chernikov et al.[4,10] measuring |Ebind(X0)| ~ 320 meV for uncovered Si/SiO2/WS2 devices similar to ours, and showing 1 meV red-shift in Pos(X0) per ~6 meV decrease in the exciton binding energy
Summary
We report a combined theoretical/experimental study of dynamic screening of excitons in media with frequency-dependent dielectric functions. Further we show that even in the case of dynamic screening, EC binding energies can still be calculated using effectively static dielectric functions and screened interaction potentials evaluated at a certain fixed effective frequency that depends on EC symmetries. The Poisson equation wjmitehd and Hint, in terms of experimentally medium dielectric constants evaluated at each frequency ω yields the dynamically screened ω-dependent interaction potential,V(ω).
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