Non-linear Optical Spectroscopy of Excited Exciton States for Efficient Valley Coherence Generation in WSe2 Monolayers

Abstract

Monolayers (MLs) of MoS2 and WSe2 are 2D semiconductors with strong, direct optical transitions that are governed by tightly Coulomb bound eletron-hole pairs (excitons). The optoelectronic properties of these transition metal dichalcogenides are directly related to the inherent crystal inversion symmetry breaking. It allows for efficient second harmonic generation (SHG) and is at the origin of chiral optical selections rules, which enable efficient optical initialization of electrons in specific K-valleys in momentum space. Here we demonstrate how these unique non-linear and linear optical properties can be combined to efficiently prepare exciton valley coherence and polarization through resonant pumping of an excited exciton state. In particular a new approach to coherent alignment of excitons following two-photon excitation is demonstrated. We observe a clear deviation of the excited exciton spectrum from the standard Rydberg series via resonances in SHG spectroscopy and two- and one-photon absorption. The clear identification of the 2s and 2p exciton excited states combined with first principle calculations including strong anti-screening effects allows us to determine an exciton binding energy of the order of 600 meV in ML WSe2.

9 pages, 5 figures + Supplementary Information

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Cited by in corpus (41)

• Measurement of the optical dielectric function of transition metal dichalcogenide monolayers: MoS2, MoSe2, WS2 and WSe2
• Tightly bound excitons in monolayer WSe2
• k.p theory for two-dimensional transition metal dichalcogenide semiconductors
• Magnetic Control of Valley Pseudospin in Monolayer WSe2
• Valley Zeeman Effect in Elementary Optical Excitations of a Monolayer WSe2
• Electrical Control of Second-Harmonic Generation in a WSe2 Monolayer Transistor
• Valley Splitting and Polarization by the Zeeman Effect in Monolayer MoSe2
• Probing excitonic states in ultraclean suspended two-dimensional semiconductors by photocurrent spectroscopy
• Measurement of high exciton binding energy in the monolayer transition-metal dichalcogenides WS2 and WSe2
• Trion induced negative photoconductivity in monolayer MoS2
• Ultrafast Manipulation of Valley Pseudospin
• Probing the influence of dielectric environment on excitons in monolayer WSe2: Insight from high magnetic fields
• Optical imaging of strain in two-dimensional crystals
• Polarization and time-resolved photoluminescence spectroscopy of excitons in MoSe2 monolayers
• Molecular-beam epitaxy of monolayer and bilayer WSe2: A scanning tunneling microscopy/spectroscopy study and deduction of exciton binding energy
• Magneto-optics in transition metal diselenide monolayers
• Probing the spin-polarized electronic band structure in monolayer transition metal dichalcogenides by optical spectroscopy
• Directional Interlayer Spin-Valley Transfer in Two-Dimensional Heterostructures
• Electronic and optical properties of two-dimensional InSe from a DFT-parameterized tight-binding model
• Optical spectroscopy of excited exciton states in MoS2 monolayers in van der Waals heterostructures
• Engineering of Neutral Excitons and Exciton Complexes in Transition Metal Dichalcogenide Monolayers through External Dielectric Screening
• Nonlinear Optical Properties of Transition Metal Dichalcogenide MX${}_2$ (M = Mo, W; X = S, Se) Monolayers and Trilayers from First-principles Calculations
• Strongly bound Mott-Wannier Excitons in GeS and GeSe monolayers
• Intrinsic exciton states mixing and non-linear optical properties in transition metal dichalcogenide monolayers
• Opto-valleytronic imaging of atomically thin semiconductors
• Luminescent emission of excited Rydberg excitons from monolayer WSe2
• Influence of the effective layer thickness on the groundstate and excitonic properties of transition-metal dichalcogenide systems
• Exciton binding energies and luminescence of phosphorene under pressure
• Nonlinear optical selection rules of excitons in monolayer transition metal dichalcogenides
• Superior valley polarization and coherence of 2s excitons in monolayer WSe2
• Many-body effects in nonlinear optical responses of 2D layered semiconductors
• Spin-orbit coupling, optical transitions, and spin pumping in mono- and few-layer InSe
• Optical selection rules for excitonic Rydberg series in the massive Dirac cones of hexagonal 2D materials
• Population pulsation resonances of excitons in monolayer MoSe2 with sub 1 μeV linewidth
• Rigid-layer Raman-active modes in $N$-layer Transition Metal Dichalcogenides: interlayer force constants and hyperspectral Raman imaging
• Optical third harmonic generation in black phosphorus
• Computational Analysis of Dispersive and Nonlinear 2D Materials by Using a Novel GS-FDTD Method
• Spectrum of exciton states in monolayer transition metal dichalcogenides: angular momentum and Landau levels
• Layer Tunable Third-Harmonic Generation in Multilayer Black Phosphorus
• Pressure-controlled Structural Symmetry Transition in Layered InSe
• Nonlinear optics in the electron-hole continuum in 2D semiconductors: two-photon transition, second harmonic generation and valley current injection