Exciton states in monolayer MoSe2 and MoTe2 probed by upconversion spectroscopy

Abstract

Transitions metal dichalcogenides (TMDs) are direct semiconductors in the atomic monolayer (ML) limit with fascinating optical and spin-valley properties. The strong optical absorption of up to 20 % for a single ML is governed by excitons, electron-hole pairs bound by Coulomb attraction. Excited exciton states in MoSe${}_2$ and MoTe${}_2$ monolayers have so far been elusive due to their low oscillator strength and strong inhomogeneous broadening. Here we show that encapsulation in hexagonal boron nitride results in emission line width of the A:1$s$ exciton below 1.5 meV and 3 meV in our MoSe${}_2$ and MoTe${}_2$ monolayer samples, respectively. This allows us to investigate the excited exciton states by photoluminescence upconversion spectroscopy for both monolayer materials. The excitation laser is tuned into resonance with the A:1$s$ transition and we observe emission of excited exciton states up to 200 meV above the laser energy. We demonstrate bias control of the efficiency of this non-linear optical process. At the origin of upconversion our model calculations suggest an exciton-exciton (Auger) scattering mechanism specific to TMD MLs involving an excited conduction band thus generating high energy excitons with small wave-vectors. The optical transitions are further investigated by white light reflectivity, photoluminescence excitation and resonant Raman scattering confirming their origin as excited excitonic states in monolayer thin semiconductors.

arXiv comment14 pages, 7 figures, main text and appendix

References in corpus (57)

• Atomically thin MoS2: A new direct-gap semiconductor
• Van der Waals heterostructures
• 2D materials and van der Waals heterostructures
• Exciton Binding Energy and Nonhydrogenic Rydberg Series in Monolayer WS2
• Excitons in atomically thin transition metal dichalcogenides
• Observation of giant bandgap renormalization and excitonic effects in a monolayer transition metal dichalcogenide semiconductor
• Optical Spectrum of MoS${}_2$: Many-body Effects and Diversity of Exciton States
• Electrical Control of Two-Dimensional Neutral and Charged Excitons in a Monolayer Semiconductor
• Tightly bound excitons in monolayer WSe2
• k.p theory for two-dimensional transition metal dichalcogenide semiconductors
• Probing Excitonic Dark States in Single-layer Tungsten Disulfide
• Dielectric screening in two-dimensional insulators: Implications for excitonic and impurity states in graphane
• Excitonic linewidth approaching the homogeneous limit in MoS2 based van der Waals heterostructures : accessing spin-valley dynamics
• Non-linear Optical Spectroscopy of Excited Exciton States for Efficient Valley Coherence Generation in WSe2 Monolayers
• Excitonic linewidth and coherence lifetime in monolayer transition metal dichalcogenides
• Exciton Radiative Lifetime in Transition Metal Dichalcogenide Monolayers
• Indirect-to-direct band-gap crossover in few-layer MoTe${}_2$
• Structural Semiconductor-to-Semimetal Phase Transition in Two-Dimensional Materials Induced by Electrostatic Gating
• Exciton-exciton annihilation in MoSe2 monolayers
• Room-temperature Continuous-wave Lasing from Monolayer Molybdenum Ditelluride with a Silicon Nanobeam Cavity
• Exciton fine structure and spin decoherence in monolayers of transition metal dichalcogenides
• Magneto-Optics of Exciton Rydberg States in a Monolayer Semiconductor
• Nonlinear Photoluminescence in Atomically Thin Layered WSe2 Arising from Diffusion-Assisted Exciton-Exciton Annihilation
• Probing the influence of dielectric environment on excitons in monolayer WSe2: Insight from high magnetic fields
• Atomically thin mirrors made of monolayer semiconductors
• Valley-spin polarized Landau levels in a monolayer semiconductor
• Phonon Sidebands in Transition Metal Dichalcogenides
• Fundamental Limits of Exciton-Exciton Annihilation for Light Emission in Transition Metal Dichalcogenide Monolayers
• Polarization and time-resolved photoluminescence spectroscopy of excitons in MoSe2 monolayers
• Engineering the structural and electronic phases of MoTe2 through W substitution
• Direct exciton emission from atomically thin transition metal dichalcogenide heterostructures near the lifetime limit
• Resonance effects in the Raman scattering of mono- and few layers MoSe${}_2$
• Enabling valley selective exciton scattering in monolayer WSe${}_2$ through upconversion
• Exciton-phonon coupling in MoSe2 monolayers
• Exciton-exciton interaction in transition-metal dichalcogenide monolayers
• Auger Recombination in Semiconductor Quantum Wells
• Double resonance Raman modes in mono- and few-layer MoTe${}_2$
• Optical spectroscopy of excited exciton states in MoS2 monolayers in van der Waals heterostructures
• Giant paramagnetism induced valley polarization of electrons in charge-tunable monolayer MoSe2
• Coherent and Incoherent Coupling Dynamics between Neutral and Charged Excitons in Monolayer MoSe2
• Large effective mass and interaction-enhanced Zeeman splitting of $K$-valley electrons in MoSe${}_2$
• Density-Dependent Quantum Hall States and Zeeman Splitting in Monolayer and Bilayer WSe${}_2$
• Raman scattering excitation spectroscopy in monolayer WS${}_2$
• Unusual Exciton-Phonon Interactions at van der Waals Engineered Interfaces
• Zeeman Splitting and Inverted Polarization of Biexciton Emission in Monolayer WS2
• Zeeman splitting via spin-valley-layer coupling in bilayer MoTe2
• Exciton states in monolayer MoSe2: impact on interband transitions
• Excitonic properties of semiconducting monolayer and bilayer MoTe2
• Double resonant Raman scattering and valley coherence generation in monolayer WSe2
• Direct versus indirect band gap emission and exciton-exciton annihilation in atomically thin molybdenum ditelluride (MoTe${}_2$)
• Intrinsic exciton states mixing and non-linear optical properties in transition metal dichalcogenide monolayers
• Auger decay of degenerate and Bose-condensed excitons in Cu${}_2$O
• Monolayer MoSe2: A candidate for room temperature polaritonics
• Atomically inspired $k\cdot p$ approach and valley Zeeman effect in transition metal dichalcogenide monolayers
• Superior valley polarization and coherence of 2s excitons in monolayer WSe2
• Optical Absorption by Dirac Excitons in Single-Layer Transition-Metal Dichalcogenides
• Exciton-phonon relaxation bottleneck and radiative decay of thermal exciton reservoir in two-dimensional materials

Cited by in corpus (35)

• The Coulomb interaction in monolayer transition-metal dichalcogenides
• Exciton diffusion in monolayer semiconductors with suppressed disorder
• Interacting Polaron-Polaritons
• Exciton-exciton interaction in transition metal dichalcogenide monolayers and van der Waals heterostructures
• Energy spectrum of two-dimensional excitons in a non-uniform dielectric medium
• Nonlinear quantum optics with trion-polaritons in 2D monolayers: conventional and unconventional photon blockade
• Exciton optics, dynamics and transport in atomically thin semiconductors
• Magneto-photoluminescence of exciton Rydberg states in monolayer WSe${}_2$
• Luminescent emission of excited Rydberg excitons from monolayer WSe2
• Phonon wind and drag of excitons in monolayer semiconductors
• Ground and Excited Exciton Polarons in Monolayer MoSe2
• Nonlinear optical selection rules of excitons in monolayer transition metal dichalcogenides
• Spinorial formulation of the GW-BSE equations and spin properties of excitons in 2D Transition Metal Dichalcogenides
• Dark exciton-exciton annihilation in monolayer WSe${}_2$
• Harnessing Exciton-Exciton Annihilation in Two-Dimensional Semiconductors
• Transferable screened range-separated hybrid functionals for electronic and optical properties of van der Waals materials
• Nonlinear optics in 2D materials: from classical to quantum
• Exciton-phonon interaction calls for a revision of the "exciton" concept
• Magneto-spectroscopy of exciton Rydberg states in a CVD grown WSe2 monolayer
• Phonon-assisted exciton and trion conversion efficiency in transition metal Dichalcogenides
• 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
• Direct Observation of Intravalley Phonon Scattering of 2s Excitons in MoSe${}_2$ and WSe${}_2$ Monolayers
• Quasiparticle and Optical Properties of Carrier-Doped Monolayer MoTe${}_2$ from First Principles
• Magnetoexcitons in transition-metal dichalcogenides monolayers, bilayers, and van der Waals heterostructures
• Phonon signatures in spectra of exciton polaritons in transition metal dichalcogenides
• Excited-State Trions in Two Dimensional Materials
• Effects of parallel electric and magnetic fields on Rydberg excitons in buckled two-dimensional materials
• Enhanced exciton-exciton collisions in an ultra-flat monolayer MoSe2 prepared through deterministic flattening
• Imaging Seebeck drift of excitons and trions in MoSe2 monolayers
• Viscous hydrodynamics of excitons in van der Waals heterostructures
• Magnetoexcitons in phosphorene monolayers, bilayers, and van der Waals heterostructures
• Ultrafast transient absorption spectroscopy of 2D semiconductors: a review
• Disorder of Excitons and Trions in Monolayer MoSe2
• Microscopic Theory of Exciton-Exciton Annihilation in Two-Dimensional Semiconductors