Many-body effects in nonlinear optical responses of 2D layered semiconductors

Abstract

We performed ultrafast degenerate pump-probe spectroscopy on monolayer WSe2 near its exciton resonance. The observed differential reflectance signals exhibit signatures of strong many-body interactions including the exciton-exciton interaction and free carrier induced band gap renormalization. The exciton-exciton interaction results in a resonance blue shift which lasts for the exciton lifetime (several ps), while the band gap renormalization manifests as a resonance red shift with several tens ps lifetime. Our model based on the many-body interactions for the nonlinear optical susceptibility fits well the experimental observations. The power dependence of the spectra shows that with the increase of pump power, the exciton population increases linearly and then saturates, while the free carrier density increases superlinearly, implying that exciton Auger recombination could be the origin of these free carriers. Our model demonstrates a simple but efficient method for quantitatively analyzing the spectra, and indicates the important role of Coulomb interactions in nonlinear optical responses of such 2D materials.

References in corpus (10)

• Valley polarization in MoS2 monolayers by optical pumping
• Observation of giant bandgap renormalization and excitonic effects in a monolayer transition metal dichalcogenide semiconductor
• Tightly bound excitons in monolayer WSe2
• Probing Excitonic Dark States in Single-layer Tungsten Disulfide
• Exciton Binding Energy of Monolayer WS2
• Non-linear Optical Spectroscopy of Excited Exciton States for Efficient Valley Coherence Generation in WSe2 Monolayers
• Measurement of high exciton binding energy in the monolayer transition-metal dichalcogenides WS2 and WSe2
• Nonlinear Photoluminescence in Atomically Thin Layered WSe2 Arising from Diffusion-Assisted Exciton-Exciton Annihilation
• Auger recombination of dark excitons in $\mathrm{W}{\mathrm{S}}_2$ and $\mathrm{WS}{\mathrm{e}}_2$ monolayers
• Population pulsation resonances of excitons in monolayer MoSe2 with sub 1 μeV linewidth

Cited by in corpus (7)

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• Direct Determination of Band Gap Renormalization in Photo-Excited Monolayer MoS2
• Exciton-exciton interaction in transition-metal dichalcogenide monolayers
• Upconverted electroluminescence via Auger scattering of interlayer excitons in van der Waals heterostructures
• Efficient ionization of two dimensional excitons by intense single cycle terahertz pulses
• Non-adiabatic suppression of 3D excitonic screening in black phosphorus by mid-infrared pulses