Browse
Submit Data
Databases
API
Help

Dataset Information

46 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Phonon-Assisted Photoluminescence from Indirect Excitons in Monolayers of Transition-Metal Dichalcogenides.

ABSTRACT: The photoluminescence (PL) spectrum of transition-metal dichalcogenides (TMDs) shows a multitude of emission peaks below the bright exciton line, and not all of them have been explained yet. Here, we study the emission traces of phonon-assisted recombinations of indirect excitons. To this end, we develop a microscopic theory describing simultaneous exciton, phonon, and photon interaction and including consistent many-particle dephasing. We explain the drastically different PL below the bright exciton in tungsten- and molybdenum-based materials as the result of different configurations of bright and momentum-dark states. In good agreement with experiments, our calculations predict that WSe2 exhibits clearly visible low-temperature PL signals stemming from the phonon-assisted recombination of momentum-dark K-K' excitons.

SUBMITTER: Brem S

PROVIDER: S-EPMC7307964 | biostudies-literature | 2020 Apr

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Publications

Phonon-Assisted Photoluminescence from Indirect Excitons in Monolayers of Transition-Metal Dichalcogenides.

Brem Samuel S Ekman August A Christiansen Dominik D Katsch Florian F Selig Malte M Robert Cedric C Marie Xavier X Urbaszek Bernhard B Knorr Andreas A Malic Ermin E

Nano letters 20200305 4

The photoluminescence (PL) spectrum of transition-metal dichalcogenides (TMDs) shows a multitude of emission peaks below the bright exciton line, and not all of them have been explained yet. Here, we study the emission traces of phonon-assisted recombinations of indirect excitons. To this end, we develop a microscopic theory describing simultaneous exciton, phonon, and photon interaction and including consistent many-particle dephasing. We explain the drastically different PL below the bright ex ...[more]

PMID: 32084315

Similar Datasets

Nano-spectroscopy of excitons in atomically thin transition metal dichalcogenides.

Project description:Excitons play a dominant role in the optoelectronic properties of atomically thin van der Waals (vdW) semiconductors. These excitons are amenable to on-demand engineering with diverse control knobs, including dielectric screening, interlayer hybridization, and moiré potentials. However, external stimuli frequently yield heterogeneous excitonic responses at the nano- and meso-scales, making their spatial characterization with conventional diffraction-limited optics a formidable task. Here, we use a scattering-type scanning near-field optical microscope (s-SNOM) to acquire exciton spectra in atomically thin transition metal dichalcogenide microcrystals with previously unattainable 20 nm resolution. Our nano-optical data revealed material- and stacking-dependent exciton spectra of MoSe2, WSe2, and their heterostructures. Furthermore, we extracted the complex dielectric function of these prototypical vdW semiconductors. s-SNOM hyperspectral images uncovered how the dielectric screening modifies excitons at length scales as short as few nanometers. This work paves the way towards understanding and manipulation of excitons in atomically thin layers at the nanoscale.

| S-EPMC8795359 | biostudies-literature

Cavity-Tuned Exciton Dynamics in Transition Metal Dichalcogenides Monolayers.

Project description:A fully quantum, numerically accurate methodology is presented for the simulation of the exciton dynamics and time-resolved fluorescence of cavity-tuned two-dimensional (2D) materials at finite temperatures. This approach was specifically applied to a monolayer WSe2 system. Our methodology enabled us to identify the dynamical and spectroscopic signatures of polaronic and polaritonic effects and to elucidate their characteristic timescales across a range of exciton-cavity couplings. The approach employed can be extended to simulation of various cavity-tuned 2D materials, specifically for exploring finite temperature nonlinear spectroscopic signals.

| S-EPMC11356741 | biostudies-literature

Macroscopic transition metal dichalcogenides monolayers with uniformly high optical quality.

Project description:The unique optical properties of transition metal dichalcogenide (TMD) monolayers have attracted significant attention for both photonics applications and fundamental studies of low-dimensional systems. TMD monolayers of high optical quality, however, have been limited to micron-sized flakes produced by low-throughput and labour-intensive processes, whereas large-area films are often affected by surface defects and large inhomogeneity. Here we report a rapid and reliable method to synthesize macroscopic-scale TMD monolayers of uniform, high optical quality. Using 1-dodecanol encapsulation combined with gold-tape-assisted exfoliation, we obtain monolayers with lateral size > 1 mm, exhibiting exciton energy, linewidth, and quantum yield uniform over the whole area and close to those of high-quality micron-sized flakes. We tentatively associate the role of the two molecular encapsulating layers as isolating the TMD from the substrate and passivating the chalcogen vacancies, respectively. We demonstrate the utility of our encapsulated monolayers by scalable integration with an array of photonic crystal cavities, creating polariton arrays with enhanced light-matter coupling strength. This work provides a pathway to achieving high-quality two-dimensional materials over large areas, enabling research and technology development beyond individual micron-sized devices.

| S-EPMC10067954 | biostudies-literature

Enhanced Photoluminescence of Solution-Exfoliated Transition Metal Dichalcogenides by Laser Etching.

Project description:Using a conventional Raman experimental apparatus, we demonstrate that the photoluminescent (PL) yield from ultrasonication-exfoliated transition metal dichalcogenides (TMDs) (MoS2 and WS2) can be increased by up to 8-fold by means of a laser etching procedure. This laser etching process allows us to controllably pattern and reduce the number of layers of the solution-exfoliated material, overcoming the key drawback to solvent-based exfoliation of two-dimensional (2D) semiconducting materials for applications in optoelectronics. The successful laser thinning of the exfoliated 2D crystals was investigated systematically by changes in both Raman and PL spectra. A simple proof-of-principle of the scalability of this laser etching technique for solution-exfoliated TMD crystals was also demonstrated. As well as being applicable for individual materials, it is also possible to use this simple laser etching technique to investigate the structure of solution-generated van der Waals heterostructures, consisting of layers of both MoS2 and WS2.

| S-EPMC6641068 | biostudies-literature

Direct probing of phonon mode specific electron-phonon scatterings in two-dimensional semiconductor transition metal dichalcogenides.

Project description:Electron-phonon scatterings in solid-state systems are pivotal processes in determining many key physical quantities such as charge carrier mobilities and thermal conductivities. Here, we report direct probing of phonon mode specific electron-phonon scatterings in layered semiconducting transition metal dichalcogenides WSe2, MoSe2, WS2, and MoS2 through inelastic electron tunneling spectroscopy measurements, quantum transport simulations, and density functional calculation. We experimentally and theoretically characterize momentum-conserving single- and two-phonon electron-phonon scatterings involving up to as many as eight individual phonon modes in mono- and bilayer films, among which transverse, longitudinal acoustic and optical, and flexural optical phonons play significant roles in quantum charge flows. Moreover, the layer-number sensitive higher-order inelastic electron-phonon scatterings, which are confirmed to be generic in all four semiconducting layers, can be attributed to differing electronic structures, symmetry, and quantum interference effects during the scattering processes in the ultrathin semiconducting films.

| S-EPMC8313722 | biostudies-literature

Intrinsic homogeneous linewidth and broadening mechanisms of excitons in monolayer transition metal dichalcogenides.

Project description:The band-edge optical response of transition metal dichalcogenides, an emerging class of atomically thin semiconductors, is dominated by tightly bound excitons localized at the corners of the Brillouin zone (valley excitons). A fundamental yet unknown property of valley excitons in these materials is the intrinsic homogeneous linewidth, which reflects irreversible quantum dissipation arising from system (exciton) and bath (vacuum and other quasiparticles) interactions and determines the timescale during which excitons can be coherently manipulated. Here we use optical two-dimensional Fourier transform spectroscopy to measure the exciton homogeneous linewidth in monolayer tungsten diselenide (WSe2). The homogeneous linewidth is found to be nearly two orders of magnitude narrower than the inhomogeneous width at low temperatures. We evaluate quantitatively the role of exciton-exciton and exciton-phonon interactions and population relaxation as linewidth broadening mechanisms. The key insights reported here—strong many-body effects and intrinsically rapid radiative recombination—are expected to be ubiquitous in atomically thin semiconductors.

| S-EPMC4595717 | biostudies-literature

3D hydrogen-like screening effect on excitons in hBN-encapsulated monolayer transition metal dichalcogenides.

Project description:We observe both s-series and p-series excitons by using sum frequency generation spectroscopy on monolayer (1L-)MX2 (M = Mo, W, X = S, Se) encapsulated by hexagonal boron nitride (hBN). Moreover, we perform numerical calculations with the Rytova-Keldysh potential and obtain the relative dielectric constant of hBN among other parameters. The obtained relative dielectric constant can be approximated by the high-frequency limit of the infrared dispersion even though the exciton binding energies are almost on the phonon resonances in hBN. This suggests that the theoretically indicated modification of the exciton level structure due to the phonon resonances is negligible. The power-law scaling of exciton binding energies indicates that dielectric screening of 1L-MX2 exciton levels other than 1s can be approximated by that of a 3D hydrogen model with the dielectric constant of hBN.

| S-EPMC11549476 | biostudies-literature

Toward Phonon-Limited Transport in Two-Dimensional Transition Metal Dichalcogenides by Oxygen-Free Fabrication.

Project description:Developing future electronics will require aggressive scaling of the channel material thickness while maintaining device performance. Two-dimensional (2D) semiconductors are promising candidates to sustain further device scaling, but despite more than two decades of intense research, experimental performance continues to lag theoretical expectations. Here, we develop an oxygen-free approach to fabricate 2D field-effect transistors and push the electrical transport toward the theoretical phonon-limited intrinsic mobility. This approach achieves record carrier mobilities of 91 and 132 cm2 V-1 s-1 for mono- and bilayer MoS2 transistors on silicon oxide substrates. Statistical analysis of over 60 MoS2 and WS2 devices confirms that oxygen-free fabrication enhances device performance by more than an order of magnitude across key figures of merit. While previous studies suggest that 2D transition metal dichalcogenides such as MoS2 and WS2 are relatively stable in air, we show that even short-term ambient exposure can degrade their performance. We identify oxygen as a crucial factor in limiting transistor performance through irreversible chemisorption. This study emphasizes the criticality of avoiding oxygen exposure and offers guidance for device manufacturing that impacts fundamental research and practical applications of 2D materials.

| S-EPMC11912576 | biostudies-literature

Enhanced performance of in-plane transition metal dichalcogenides monolayers by configuring local atomic structures.

Project description:The intrinsic activity of in-plane chalcogen atoms plays a significant role in the catalytic performance of transition metal dichalcogenides (TMDs). A rational modulation of the local configurations is essential to activating the in-plane chalcogen atoms but restricted by the high energy barrier to break the in-plane TM-X (X = chalcogen) bonds. Here, we theoretically design and experimentally realize the tuning of local configurations. The electron transfer capacity of local configurations is used to screen suitable TMDs materials for hydrogen evolution reaction (HER). Among various configurations, the triangular-shape cobalt atom cluster with a central sulfur vacancy (3CoMo-VS) renders the distinct electrocatalytic performance of MoS2 with much reduced overpotential and Tafel slope. The present study sheds light on deeper understanding of atomic-scale local configuration in TMDs and a methodology to boost the intrinsic activity of chalcogen atoms.

| S-EPMC7205865 | biostudies-literature

Large Biaxial Compressive Strain Tuning of Neutral and Charged Excitons in Single-Layer Transition Metal Dichalcogenides.

Project description:The absorption and emission of light in single-layer transition metal dichalcogenides are governed by the formation of excitonic quasiparticles. Strain provides a powerful technique to tune the optoelectronic properties of two-dimensional materials and thus to adjust their exciton energies. The effects of large compressive strain in the optical spectrum of two-dimensional (2D) semiconductors remain rather unexplored compared to those of tensile strain, mainly due to experimental constraints. Here, we induced large, uniform, biaxial compressive strain (∼1.2%) by cooling, down to 10 K, single-layer WS2, MoS2, WSe2, and MoSe2 deposited on polycarbonate substrates. We observed a significant strain-induced modulation of neutral exciton energies, with blue shifts up to 160 meV, larger than in any previous experiments. Our results indicate a remarkably efficient transfer of compressive strain, demonstrated by gauge factor values exceeding previous results and approaching theoretical expectations. At low temperatures, we investigated the effect of compressive strain on the resonances associated with the formation of charged excitons. In WS2, a notable reduction of gauge factors for charged compared to neutral excitons suggests an increase in their binding energy, which likely results from the effects of strain added to the influence of the polymeric substrate.

| S-EPMC10726316 | biostudies-literature

OmicsDI is part of the ELIXIR infrastructure

OmicsDI is an Elixir interoperability service. Learn more ›

Tweets

OmicsDI Databases

PRIDE
PeptideAtlas
MassIVE
JPOST Repository
Physiome Model Repository

EGA
EVA
ENA
LINCS
PAXDB
Cell Collective

MetaboLights
Metabolomics Workbench
MetabolomeExpress
GNPS
BioModels
FAIRDOMHub

ArrayExpress
dbGaP
ExpressionAtlas
GEO
NODE

Information

Databases
Help
API
Contact us
Code on GitHub
Terms of use
Submit Data