Resonance profiles of valley polarization in single-layer MoS${}_2$ and MoSe${}_2$

Abstract

In this letter we present photoluminescence measurements with different excitation energies on single-layer MoS${}_2$ and MoSe${}_2$ in order to examine the resonance behavior of the conservation of circular polarization in these transition metal dichalcogenides. We find that the circular polarization of the emitted light is conserved to 100% in MoS${}_2$ and 84% / 79% (A/A${}^{-}$ peaks) in MoSe${}_2$ close to resonance. The values for MoSe${}_2$ surpass any previously reported value. However, in contrast to previous predictions, the degree of circular polarization decreases clearly at energies less than the two-phonon longitudinal acoustic phonon energy above the resonance. Our findings indicate that at least two competing processes underly the depolarization of the emission in single-layer transition metal dichalcogenides.

References in corpus (6)

• Valley polarization in MoS2 monolayers by optical pumping
• Robust optical emission polarization in MoS2 monolayers through selective valley excitation
• Exciton Valley Dynamics probed by Kerr Rotation in WSe2 Monolayers
• Phonon Softening and Direct to Indirect Bandgap Crossover in Strained Single Layer MoSe2
• Newly observed first-order resonant Raman modes in few-layer MoS${}_2$
• Dark excitons and the elusive valley polarization in transition metal dichalcogenides

Cited by in corpus (19)

• Measurement of the Spin-Forbidden Dark Excitons in MoS2 and MoSe2 monolayers
• Guide to optical spectroscopy of layered semiconductors
• Phonon dispersion of MoS${}_2$
• Ultrafast dynamics in monolayer TMDCs: the interplay of dark excitons, phonons and intervalley Coulomb exchange
• Optical control of valley Zeeman effect through many-exciton interactions
• Exciton valley depolarization in monolayer transition-metal dichalcogenides
• Quenching of Intervalley Exchange Coupling in the Presence of Momentum-Dark States in TMDCs
• Prolonging Valley Polarization Lifetime through Gate-Controlled Exciton-to-Trion Conversion in Monolayer Molybdenum Ditelluride
• Enhancement of Exciton Valley Polarization in Monolayer MoS2 Induced by Scattering
• Valley Degree of Freedom in Two-Dimensional van der Waals Materials
• Strain control of exciton and trion spin-valley dynamics in monolayer transition metal dichalcogenides
• Ultrafast pseudospin quantum beats in multilayer WSe${}_2$ and MoSe${}_2$
• Valley Depolarization in Monolayer Transition-Metal Dichalcogenides with Zone-Corner Acoustic Phonons
• Inducing room-temperature valley polarization of excitonic emission in transition metal dichalcogenide monolayers
• Impact of optically pumped non-equilibrium steady states on luminescence emission of atomically-thin semiconductor excitons
• Realization of valley-spin polarized current via parametric pump in monolayer $\mathrm{Mo}{\mathrm{S}}_2$
• Enhanced interlayer electron transfer by surface treatments in mixed-dimensional van der Waals semiconductor heterostructures
• Two-color Kerr microscopy of two-dimensional materials with sub-picosecond time resolution
• Optical Measurement of Pseudo-Spin Texture of the Exciton Fine-Structure in Monolayer WSe2 within the Light Cone