Optical properties of atomically thin transition metal dichalcogenides: Observations and puzzles

Abstract

Recent results on the optical properties of mono- and few-layers of semiconducting transition metal dichalcogenides are reviewed. Experimental observations are presented and discussed in the frame of existing models, highlighting the limits of our understanding in this emerging field of research. We first introduce the representative band structure of these systems and their interband optical transitions. The effect of an external magnetic field is then considered to discuss Zeeman spectroscopy and optical pumping experiments, both revealing phenomena related to the valley degree of freedom. Finally, we discuss the observation of single photon emitters in different types of layered materials, including wide band gap hexagonal boron nitride. While going through these topics, we try to focus on open questions and on experimental observations, which do not yet have a clear explanation.

41 pages, 18 figures

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• Strain-induced spatial and spectral isolation of quantum emitters in mono- and bi-layer WSe2
• Direct Measurement of Exciton Valley Coherence in Monolayer WSe${}_2$
• Exciton fine structure and spin decoherence in monolayers of transition metal dichalcogenides
• Exciton Valley Dynamics probed by Kerr Rotation in WSe2 Monolayers
• Nonanalyticity, Valley Quantum Phases, and Light-like Exciton Dispersion in Monolayer TMDs: Theory and First-Principles Calculations
• WSe2 light-emitting tunneling transistors with enhanced brightness at room temperature
• Brightening of dark excitons in monolayers of semiconducting transition metal dichalcogenides
• Valley Carrier Dynamics in Monolayer Molybdenum Disulphide from Helicity Resolved Ultrafast Pump-probe Spectroscopy
• Spin-orbit engineering in transition metal dichalcogenide alloy monolayers
• Structural attributes and photo-dynamics of visible spectrum quantum emitters in hexagonal boron nitride
• Optical Signatures of Quantum Emitters in Suspended Hexagonal Boron Nitride
• Probing critical point energies of transition metal dichalcogenides: surprising indirect gap of single layer $SL-WS{e}_2$
• Exciton band structure in layered MoSe2: from a monolayer to the bulk limit
• Efficient single photon emission from a high-purity hexagonal boron nitride crystal
• Shubnikov-de Haas oscillations of high mobility holes in monolayer and bilayer WSe${}_2$: Landau level degeneracy, effective mass, and negative compressibility
• Polarization and time-resolved photoluminescence spectroscopy of excitons in MoSe2 monolayers
• Polarization analysis of excitons in monolayer and bilayer transition-metal dichalcogenides
• Probing the Role of Interlayer Coupling and Coulomb Interactions on Electronic Structure in Few-Layer MoSe2 Nanostructures
• Magneto-optics in transition metal diselenide monolayers
• Spin and valley dynamics of excitons in transition metal dichalcogenides monolayers
• Optical investigation of monolayer and bulk tungsten diselenide (WSe${}_2$) in high magnetic fields
• Cascaded emission of single photons from the biexciton in monolayered WSe2
• Discrete quantum dot like emitters in monolayer MoSe2: Spatial mapping, Magneto-optics and Charge tuning
• Excitonic Fano Resonance in Freestanding Graphene
• Three-particle Complexes in Two-Dimensional Semiconductors
• Spin-flip processes and radiative decay of dark intravalley excitons in transition metal dichalcogenide monolayers
• Electrically pumped single-defect light emitters in WSe${}_2$
• Excitonic properties of semiconducting monolayer and bilayer MoTe2
• Tuning valley polarization in a WSe2 monolayer with a tiny magnetic field
• Magneto-excitons in large area CVD grown monolayer MoS${}_2$ and MoSe${}_2$ on sapphire
• Symmetry preserving lattice collapse in tetragonal SrFe_(2-x)Ru_xAs_2 (x = 0, 0.2) -- a combined experimental and theoretical study
• Auger recombination of dark excitons in $\mathrm{W}{\mathrm{S}}_2$ and $\mathrm{WS}{\mathrm{e}}_2$ monolayers
• Spin-valley relaxation and quantum transport regimes in two-dimensional transition metal dichalcogenides

Cited by in corpus (90)

• Exciton physics and device application of two-dimensional transition metal dichalcogenide semiconductors
• Atomically thin quantum light emitting diodes
• Radiative control of dark excitons at room temperature by nano-optical antenna-tip induced Purcell effect
• Enhanced Light-Matter Interaction in Two-Dimensional Transition Metal Dichalcogenides
• Nanophotonics with 2D Transition Metal Dichalcogenides
• Phonon-assisted Photoluminescence from Dark Excitons in Monolayers of Transition Metal Dichalcogenides
• Measurement of the Spin-Forbidden Dark Excitons in MoS2 and MoSe2 monolayers
• Localized inter-valley defect excitons as single-photon emitters in WSe${}_2$
• Giant Zeeman splitting inducing near-unity valley polarization in van der Waals heterostructures
• Exciton-phonon coupling in MoSe2 monolayers
• Optical response of monolayer, few-layer and bulk tungsten disulfide
• Exciton g-factors of van der Waals heterostructures from first principles calculations
• Controlling interlayer excitons in MoS2 layers grown by chemical vapor deposition
• Accessing high optical quality of MoS2 monolayers grown by chemical vapor deposition
• The role of momentum-dark excitons in the elementary optical response of bilayer WSe${}_2$
• Site-Controlled Telecom Single-Photon Emitters in Atomically-thin MoTe2
• Raman scattering excitation spectroscopy in monolayer WS${}_2$
• Giant Valley-Zeeman Splitting from Spin-Singlet and Spin-Triplet Interlayer Excitons in WSe2/MoSe2 Heterostructure
• Energy spectrum of two-dimensional excitons in a non-uniform dielectric medium
• Exciton g-factors in monolayer and bilayer WSe${}_2$ from experiment and theory
• Singlet and triplet trions in WS${}_2$ monolayer encapsulated in hexagonal boron nitride
• The valley Zeeman effect in inter- and intra-valley trions in monolayer WSe${}_2$
• Probing and manipulating valley coherence of dark excitons in monolayer WSe${}_2$
• Identifying defect-related quantum emitters in monolayer WSe${}_2$
• Coupling of deterministically activated quantum emitters in hexagonal boron nitride to plasmonic surface lattice resonances
• Dynamical screening in monolayer transition-metal dichalcogenides and its manifestations in the exciton spectrum
• Marrying excitons and plasmons in monolayer transition-metal dichalcogenides
• Dark trions govern the temperature-dependent optical absorption and emission of doped atomically thin semiconductors
• Excitonic effects in the optical properties of 2D materials: An equation of motion approach
• Valley Zeeman effect and Landau levels in Two-Dimensional Transition Metal Dichalcogenides
• Efficient phonon cascades in hot photoluminescence of WSe${}_2$ monolayers
• Excitonic complexes in $n$-doped WS${}_2$ monolayer
• Carbon and vacancy centers in hexagonal boron nitride
• Magnetooptics of layered two-dimensional semiconductors and heterostructures: progress and prospects
• Fine structure of $\mathrm{K}$-excitons in multilayers of transition metal dichalcogenides
• Nanoscale modification of WS${}_2$ trion emission by its local electromagnetic environment
• Spinorial formulation of the GW-BSE equations and spin properties of excitons in 2D Transition Metal Dichalcogenides
• Rydberg series of dark excitons and the conduction band spin-orbit splitting in monolayer WSe${}_2$
• Momentum-Resolved Exciton Coupling and Valley Polarization Dynamics in Monolayer WS${}_2$
• Neutral and charged dark excitons in monolayer WS${}_2$
• Low-frequency Raman scattering in WSe${}_2$-MoSe${}_2$ heterobilayers: Evidence for atomic reconstruction
• Radiative lifetime of localized excitons in transition metal dichalcogenides
• Exciton spectroscopy and diffusion in MoSe2-WSe2 lateral heterostructures encapsulated in hexagonal boron nitride
• Zeeman spectroscopy of excitons and hybridization of electronic states in few-layer WSe${}_2$, MoSe${}_2$ and MoTe${}_2$
• Highly Sensitive, Fast Graphene Photodetector with Responsivity $>10^6$ A/W Using Floating Quantum Well Gate
• Tunneling-current-induced local excitonic luminescence in p-doped WSe${}_2$ monolayers
• The optical signature of few-layer ReSe${}_2$
• Light-matter interaction in van der Waals heterostructures
• Tuning carrier concentration in a superacid treated MoS${}_2$ monolayer
• 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
• Field-induced hybridization of moiré excitons in MoSe${}_2$/WS${}_2$ heterobilayers
• Inter-layer charge transport controlled by exciton-trion coherent coupling
• Exciton-polaritons in multilayer WSe${}_2$ in a planar microcavity
• Analytical description of the 1s exciton linewidth temperature-dependence in transition metal dichalcogenides
• Local field effects in ultrafast light-matter interaction measured by pump-probe spectroscopy of monolayer MoSe${}_2$
• Resonance and antiresonance in Raman scattering in GaSe and InSe crystals
• The optical response of artificially twisted MoS${}_2$ bilayers
• Excitation-Dependent High-Lying Excitonic Exchange via Interlayer Energy Transfer from Lower-to-Higher Bandgap 2D Material
• The effect of dielectric environment on the brightening of neutral and charged dark excitons in WSe${}_2$ monolayer
• Calculation of the nonlinear response functions of intra-exciton transitions in two-dimensional transition metal dichalcogenides
• Excitons and trions in WSSe monolayers
• ZnPSe${}_3$ as ultrabright indirect bandgap system with microsecond excitonic lifetimes
• Large g factor in bilayer WS${}_2$ flakes
• Analogy and dissimilarity of excitons in monolayer and bilayer of MoSe${}_2$
• Spin-orbit-stable type-II nodal line band crossing in n-doped monolayer MoX2 (X=S,Se,Te)
• Interplay of energy and charge transfer in WSe2/CrSBr heterostructures
• Third-order Optical Nonlinearity in Two-dimensional Transition Metal Dichalcogenides
• Microscopic theory of the polarizability of transition metal dichalcogenides excitons: Application to WSe2
• Semiconductor Bloch equation analysis of optical Stark and Bloch-Siegert shifts in monolayers WSe${}_2$ and MoS${}_2$
• Raman scattering excitation in monolayers of semiconducting transition metal dichalcogenides
• Dark exciton energy splitting in monolayer WSe2: insights from time-dependent density-functional theory
• Large photoluminescence enhancement by an out-of-plane magnetic field in exfoliated WS${}_2$ flakes
• Third-order polarizability of interlayer excitons in hetero-bilayers
• Effect of electron-irradiation on layered quantum materials
• Excitonic luminescence of iodine-intercalated HfS${}_2$
• Ab-initio study of the energy competition between Γand K valleys in bilayer transition metal dichalcogenides
• Multidimensional sensing of proximity magnetic fields via intrinsic activation of dark excitons in WSe${}_2$/CrCl${}_3$ heterostructure
• Theory of field-modulated spin-valley-orbital pseudospin physics
• Extremely high excitonic $g$-factors in 2D crystals by alloy-induced admixing of band states
• Magneto-Excitonic Duality From Monolayer to Trilayer CrSBr
• Optical response of WSe${}_2$-based vertical tunneling junction
• Rydberg series of intralayer K-excitons in WSe${}_2$ multilayers
• Spectral asymmetry of phonon sideband luminescence in monolayer and bilayer WSe2
• Electrically modulated light-emitting diodes driven by resonant and antiresonant tunneling between Cr${}_2$Ge${}_2$Te${}_6$ electrodes
• Reversible engineering the spin-orbit coupling of monolayer MoS2 via laser irradiation under controlled gas atmospheres
• Valley-Selective Response of Nanoantennas Coupled to 2D Transition Metal Dichalcogenides
• Increased formation of trions and charged biexcitons by above-gap excitation in single-layer $WS{e}_2$
• Raman scattering fingerprints of the charge density wave state in one-dimensional NbTe${}_4$