Direct Measurement of Exciton Valley Coherence in Monolayer WSe${}_2$

Abstract

In crystals, energy band extrema in momentum space can be identified by their valley index. The internal quantum degree of freedom associated with valley pseudospin indices can act as a useful information carrier analogous to electronic charge or spin. Interest in valleytronics has been revived in recent years following the discovery of atomically thin materials such as graphene and transition metal dichalcogenides. However, the valley coherence time, a key quantity for manipulating the valley pseudospin, has never been measured in any material. In this work, we use a sequence of laser pulses to resonantly generate a coherent superposition of excitons (Coulomb-bound electron-hole pairs) in opposite valleys of monolayer WSe${}_2$. The imposed valley coherence persists for approximately one hundred femtoseconds. We propose that the electron-hole exchange interaction provides an important decoherence mechanism in addition to exciton population decay. Our work provides critical insight into the requirements and strategies for optical manipulation of the valley pseudospin for future valleytronics applications.

arXiv comment23 pages, 6 figures

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Cited by in corpus (92)

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• Magnetic brightening and control of dark excitons in monolayer WSe2
• Ultrafast Manipulation of Valley Pseudospin
• Optical properties of atomically thin transition metal dichalcogenides: Observations and puzzles
• Radiative control of dark excitons at room temperature by nano-optical antenna-tip induced Purcell effect
• Exciton Dynamics in Monolayer Transition Metal Dichalcogenides
• Enhanced Light-Matter Interaction in Two-Dimensional Transition Metal Dichalcogenides
• Moiré Excitons Correlated with Superlattice Structure in Twisted WSe${}_2$/WSe${}_2$ Homobilayers
• Control of Exciton Valley Coherence in Transition Metal Dichalcogenide Monolayers
• Microsecond Valley Lifetime of Defect-Bound Excitons in Monolayer WSe${}_2$
• Defect-induced modification of low-lying excitons and valley selectivity in monolayer transition metal dichalcogenides
• Biexciton fine structure in monolayer transition metal dichalcogenides
• Gate controlled spin-valley locking of resident carriers in WSe2 monolayers
• Long-Lived Valley Polarization of Intra-Valley Trions in Monolayer WSe2
• Optical spectroscopy of excited exciton states in MoS2 monolayers in van der Waals heterostructures
• Ab initio calculations of ultra-short carrier dynamics in 2D materials: valley depolarization in single-layer WSe${}_2$
• Accessing high optical quality of MoS2 monolayers grown by chemical vapor deposition
• Coherent and Incoherent Coupling Dynamics between Neutral and Charged Excitons in Monolayer MoSe2
• Spin-flip processes and radiative decay of dark intravalley excitons in transition metal dichalcogenide monolayers
• Valley coherent exciton-polaritons in a monolayer semiconductor
• Probing and manipulating valley coherence of dark excitons in monolayer WSe${}_2$
• Roadmap for Photonics with 2D Materials
• Many-Body Simulation of Two-Dimensional Electronic Spectroscopy of Excitons and Trions in Monolayer Transition-Metal Dichalcogenides
• Theory and Ab Initio Computation of the Anisotropic Light Emission in Monolayer Transition Metal Dichalcogenides
• Trion Valley Coherence in Monolayer Semiconductors
• Room Temperature Valley Polarization and Coherence in Transition Metal Dichalcogenide-Graphene van der Waals Heterostructures
• Microscopic Theory of Spin Relaxation Anisotropy in Graphene with Proximity-Induced Spin-Orbit Coupling
• Magnetooptics of layered two-dimensional semiconductors and heterostructures: progress and prospects
• Superior valley polarization and coherence of 2s excitons in monolayer WSe2
• Valley relaxation of resident electrons and holes in a monolayer semiconductor: Dependence on carrier density and the role of substrate-induced disorder
• Many-body effects in nonlinear optical responses of 2D layered semiconductors
• Exciton-Phonon Coupling and Band-Gap Renormalization in Monolayer WSe${}_2$
• Momentum-Resolved Exciton Coupling and Valley Polarization Dynamics in Monolayer WS${}_2$
• Intervalley Scattering of Interlayer Excitons in a MoS${}_2$/MoSe${}_2$/MoS${}_2$ Heterostructure in High Magnetic Field
• Phonon-assisted inter-valley scattering determines ultrafast exciton dynamics in MoSe${}_2$ bilayers
• Optical Valley Hall Effect based on Transitional Metal Dichalcogenide cavity polaritons
• Gate-defined, Accumulation-mode Quantum Dots in Monolayer and Bilayer WSe${}_2$
• Spin/valley coupled dynamics of electrons and holes at the ${\text{MoS}}_2-{\text{MoSe}}_2$ interface
• Enhancement of Exciton Valley Polarization in Monolayer MoS2 Induced by Scattering
• Nonlinear optics in 2D materials: from classical to quantum
• Tunable topological Nernst effect in 2D transition metal dichalcogenides
• Electronic Structure of Exfoliated Millimeter-Sized Monolayer WSe2 on Silicon Wafer
• Strain control of exciton and trion spin-valley dynamics in monolayer transition metal dichalcogenides
• Spin-Degenerate Regimes for Single Quantum Dots in Transition Metal Dichalcogenide Monolayers
• Valley two-qubit system in a MoS${}_2$-monolayer gated double quantum dot
• Observation of ~100% valley-coherent excitons in monolayer MoS2 through giant enhancement of valley coherence time
• Disorder Dependent Valley Properties in Monolayer WSe2
• Mott-moiré excitons
• Observation of Ultralong Valley Lifetime in WSe2/MoS2 Heterostructures
• Tunable magneto-optical properties in MoS${}_2$ via defect-induced exciton transitions
• Room Temperature Terahertz Electroabsorption Modulation by Excitons in Monolayer Transition Metal Dichalcogenides
• Controlling valley splitting and Polarization of dark- and bi-excitons in monolayer WS${}_2$ by a tilted magnetic field
• Interlayer Exciton Valleytronics in Bilayer Heterostructures Interfaced with a Metasurface
• All-optical valley switch and clock of electronic dephasing
• Interplay of valley polarization and dynamic nuclear polarization in 2D transition metal dichalcogenides
• Microscopic theory of cavity-confined monolayer semiconductors: polariton-induced valley relaxation and the prospect of enhancing and controlling the valley pseudospin by chiral strong coupling
• Engineering quantum interference in van der Waals heterostructures
• Expeditious computation of nonlinear optical properties of arbitrary order with native electronic interactions in the time domain
• Gate-tunable trion switch for excitonic device applications
• Pump-triple sum-frequency-probe spectroscopy of transition metal dichalcogenides
• Valley Phenomena in the Candidate Phase Change Material WSe${}_{2(1-x)}$Te${}_{2x}$
• Nonlinear spectroscopy of excitonic states in transition metal dichalcogenides
• Multidimensional Spectroscopy of Time-Dependent Impurities in Ultracold Fermions
• A steady state approach for studying valley relaxation using optical vortex beam
• Magnetically tunable exciton valley coherence in monolayer WS${}_2$ mediated by the electron-hole exchange and exciton-phonon interactions
• Effect of intravalley and intervalley electron-hole exchange on the nonlinear optical response of monolayer MoSe${}_2$
• First-principles study on the electrical resistivity in zirconium dichalcogenides with multi-valley bands: mode-resolved analysis of electron-phonon scattering
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• Spin dependent analysis of homogeneous and inhomogeneous exciton decoherence in magnetic fields
• Non-Hermitian theory of valley excitons in two-dimensional semiconductors
• Ultrafast all-optical generation of pure spin and valley currents
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• Microscopic many-body theory of two-dimensional coherent spectroscopy of excitons and trions in atomically thin transition metal dichalcogenides
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