Enabling valley selective exciton scattering in monolayer WSe${}_2$ through upconversion

Abstract

Excitons, Coulomb bound electron-hole pairs, are composite bosons and their interactions in traditional semiconductors lead to condensation and light amplification. The much stronger Coulomb interaction in transition metal dichalcogenides such as WSe${}_2$ monolayers combined with the presence of the valley degree of freedom is expected to provide new opportunities for controlling excitonic effects. But so far the bosonic character of exciton scattering processes remains largely unexplored in these two-dimensional (2D) materials. Here we show that scattering between B-excitons and A-excitons preferably happens within the same valley in momentum space. This leads to power dependent, negative polarization of the hot B-exciton emission. We use a selective upconversion technique for efficient generation of B-excitons in the presence of resonantly excited A-excitons at lower energy, we also observe the excited A-excitons state $2s$. Detuning of the continuous wave, low power laser excitation outside the A-exciton resonance (with a full width at half maximum of 4 meV) results in vanishing upconversion signal.

arXiv commentmain text: 8 pages, 4 figures; supplement: 4 pages, 5 figures

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• In-plane Propagation of Light in Transition Metal Dichalcogenide Monolayers: Optical Selection Rules
• Charged excitons in monolayer WSe${}_2$: experiment and theory
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• Magneto-Optics of Exciton Rydberg States in a Monolayer Semiconductor
• Fine Structure and Lifetime of Dark Excitons in Transition Metal Dichalcogenide Monolayers
• Interlayer exciton dynamics in a dichalcogenide monolayer heterostructure
• Moiré Intralayer Excitons in a MoSe${}_2$/MoS${}_2$ Heterostructure
• Exciton-phonon coupling in MoSe2 monolayers
• Exciton diffusion in monolayer semiconductors with suppressed disorder
• Quantum interference in second-harmonic generation from monolayer WSe2
• Optical spectroscopy of excited exciton states in MoS2 monolayers in van der Waals heterostructures
• Accessing high optical quality of MoS2 monolayers grown by chemical vapor deposition
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• Energy spectrum of two-dimensional excitons in a non-uniform dielectric medium
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• Ultrafast dynamics in monolayer TMDCs: the interplay of dark excitons, phonons and intervalley Coulomb exchange
• Upconverted electroluminescence via Auger scattering of interlayer excitons in van der Waals heterostructures
• Exciton states in monolayer MoSe2 and MoTe2 probed by upconversion spectroscopy
• Luminescent emission of excited Rydberg excitons from monolayer WSe2
• Long valley lifetime of free carriers in monolayer WSe2
• Twist-angle engineering of excitonic quantum interference and optical nonlinearities in stacked 2D semiconductors
• Spatial extent of the excited exciton states in WS${}_2$ monolayers from diamagnetic shifts
• Bright excitons with negative-mass electrons
• Phonon wind and drag of excitons in monolayer semiconductors
• Dependence of the hBN Layer Thickness on the Band Structure and Exciton Properties of Encapsulated WSe2 Monolayers
• Observation of forbidden phonons and dark excitons by resonance Raman scattering in few-layer WS${}_2$
• Efficient phonon cascades in hot photoluminescence of WSe${}_2$ monolayers
• Dielectric Engineering of Electronic Correlations in a van der Waals Heterostructure
• Superior valley polarization and coherence of 2s excitons in monolayer WSe2
• Valley polarized relaxation and upconversion luminescence from Tamm-Plasmon Trion-Polaritons with a MoSe2 monolayer
• Spinorial formulation of the GW-BSE equations and spin properties of excitons in 2D Transition Metal Dichalcogenides
• Autoionization and dressing of excited excitons by free carriers in monolayer WSe2
• Dark exciton-exciton annihilation in monolayer WSe${}_2$
• Harnessing Exciton-Exciton Annihilation in Two-Dimensional Semiconductors
• Quenching of Intervalley Exchange Coupling in the Presence of Momentum-Dark States in TMDCs
• Coherent dynamics and mapping of excitons in single-layer MoSe${}_2$ and WSe${}_2$ at the homogeneous limit
• Nonlinear optics in 2D materials: from classical to quantum
• Complexes of dipolar excitons in layered quasi-two-dimensional nanostructures
• Tunable optical nonlinearity for TMD polaritons dressed by a Fermi sea
• Excitons and carriers in transient absorption and time-resolved ARPES spectroscopy: an abinitio approach
• Magneto-spectroscopy of exciton Rydberg states in a CVD grown WSe2 monolayer
• Phonon-assisted exciton and trion conversion efficiency in transition metal Dichalcogenides
• Valley polarization of exciton-polaritons in monolayer WSe2 in a tunable microcavity
• Exciton-polaritons in multilayer WSe${}_2$ in a planar microcavity
• Excitonic Complexes and Emerging Interlayer Electron-Phonon Coupling in BN Encapsulated Monolayer Semiconductor Alloy: WS0.6Se1.4
• Up- and Down-Conversion between Intra- and Inter-Valley Excitons in Waveguide Coupled Monolayer WSe2
• Enhanced nonlinear interaction of polaritons via excitonic Rydberg states in monolayer WSe2
• Monolayer Semiconductor Auger Detector
• Third-order Optical Nonlinearity in Two-dimensional Transition Metal Dichalcogenides
• Insights into hyperbolic phonon polaritons in hBN using Raman scattering from encapsulated transition metal dichalcogenide layers
• Longitudinal-transverse splitting and fine structure of Fermi polarons in two-dimensional semiconductors
• Magneto-Optical Measurements of the Negatively Charged 2$s$ Exciton in WSe${}_2$
• Ultrafast transient absorption spectroscopy of 2D semiconductors: a review
• Intrinsic process for upconversion photoluminescence via $K$-momentum phonon coupling in carbon nanotubes
• Valley polarization of trions in monolayer MoSe${}_2$ interfaced with bismuth iron garnet
• Enhanced Emission from WSe2 Monolayers Coupled to Circular Bragg Gratings
• Resonant photonic crystals based on van der Waals heterostructures
• Coherence and density dynamics of excitons in a single-layer MoS${}_2$ reaching the homogeneous limit