Room Temperature Valley Polarization and Coherence in Transition Metal Dichalcogenide-Graphene van der Waals Heterostructures

Abstract

Van der Waals heterostructures made of graphene and transition metal dichalcogenides (TMD) are an emerging platform for opto-electronic, -spintronic and -valleytronic devices that could benefit from (i) strong light-matter interactions and spin-valley locking in TMDs and (ii) exceptional electron and spin transport in graphene. The operation of such devices requires significant valley polarization and valley coherence, ideally up to room temperature. Here, using a comprehensive Mueller polarimetry analysis, we report \textit{artifact-free} room temperature degrees of valley polarization up to $40\%$ and, remarkably, of valley coherence up to $20\%$ in monolayer tungsten disulfide (WS${}_2$)/graphene heterostructures. Valley contrasts have been particularly elusive in molybdenum diselenide (MoSe${}_2$), even at cryogenic temperatures. Upon interfacing monolayer MoSe${}_2$ with graphene, the room temperature degrees of valley polarization and coherence are as high as $14\%$ and $20\%$, respectively. Our results are discussed in light of recent reports of highly efficient interlayer coupling and exciton transfer in TMD/graphene heterostructures and hold promise for room temperature chiral light-matter interactions and coherent opto-valleytronic devices.

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Cited by in corpus (16)

• Enhanced Light-Matter Interaction in Two-Dimensional Transition Metal Dichalcogenides
• Filtering the photoluminescence spectra of atomically thin semiconductors with graphene
• Prominent room temperature valley polarization in WS2/graphene heterostructures grown by chemical vapor deposition
• Picosecond energy transfer in a transition metal dichalcogenide-graphene heterostructure revealed by transient Raman spectroscopy
• Engineering photonic environments for two-dimensional materials
• Observation of ~100% valley-coherent excitons in monolayer MoS2 through giant enhancement of valley coherence time
• Impact of indirect transitions on valley polarization in WS${}_2$ and WSe${}_2$
• 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
• Inducing room-temperature valley polarization of excitonic emission in transition metal dichalcogenide monolayers
• Microscopic analysis of spin-momentum locking on a geometric phase metasurface
• Biaxial strain tuning of exciton energy and polarization in monolayer WS2
• Single- and narrow-line photoluminescence in a boron nitride-supported MoSe${}_2$/graphene heterostructure
• Circular dichroism induction in WS2 by a chiral plasmonic metasurface
• Laser-patterned submicron Bi2Se3-WS2 pixels with tunable circular polarization at room temperature
• Motion of 2D exciton in momentum space leads to pseudospin distribution narrowing on the Bloch Sphere
• Ultrafast Spin Injection in Graphene via Dynamical Carrier Filtering at Transition Metal Dichalcogenide Interfaces