Incoherent phonon population and exciton-exciton annihilation in monolayer WS2 revealed by time-resolved spontaneous Raman scattering
arXiv:1909.08302 · doi:10.1364/OE.27.029949
Abstract
Atomically thin layer transition metal dichalcogenides have been intensively investigated for their rich optical properties and potential applications in nano-electronics. In this work, we study the incoherent optical phonon and exciton population dynamics in monolayer WS2 by time-resolved spontaneous Raman scattering spectroscopy. Upon excitation of the exciton transition, both the Stokes and anti-Stokes optical phonon scattering strength exhibit a large reduction. Based on the detailed balance, the optical phonon population is retrieved, which shows an instant build-up and a relaxation lifetime of around 4 ps at an exciton density E12 cm-2. The corresponding optical phonon temperature rises by 25 K, eventually, after some 10s of picoseconds, leading to a lattice heating by only around 3 K. The exciton relaxation dynamics extracted from the transient vibrational Raman response shows a strong excitation density dependence, signaling an important bi-molecular contribution to the decay. The exciton relaxation rate is found to be (70 ps)-1 and exciton-exciton annihilation rate 0.1 cm2s-1. These results provide valuable insight into the thermal dynamics after optical excitation and enhance the understanding of the fundamental exciton dynamics in two-dimensional transition metal materials.
arXiv comment16 pages, 4 figures
References in corpus (27)
- Electric Field Effect in Atomically Thin Carbon Films
- Van der Waals heterostructures
- Two-Dimensional Material Nanophotonics
- Exciton Binding Energy and Nonhydrogenic Rydberg Series in Monolayer WS2
- Evolution of Electronic Structure in Atomically Thin Sheets of WS2 and WSe2
- Extraordinary room-temperature photoluminescence in WS2 monolayers
- Phonon and Raman scattering of two-dimensional transition metal dichalcogenides from monolayer, multilayer to bulk material
- Low-temperature photocarrier dynamics in monolayer MoS2
- Exciton Binding Energy of Monolayer WS2
- Valley-selective optical Stark effect in monolayer WS2
- Photo-Induced Bandgap Renormalization Governs the Ultrafast Response of Single-Layer MoS2
- Topology-Scaling Identification of Layered Solids and Stable Exfoliated 2D Materials
- Ultrafast Generation of Pseudo-magnetic Field for Valley Excitons in WSe2 Monolayers
- Brightening of dark excitons in monolayers of semiconducting transition metal dichalcogenides
- Exciton dynamics in atomically thin MoS2: inter-excitonic interaction and broadening kinetics
- Fundamental Limits of Exciton-Exciton Annihilation for Light Emission in Transition Metal Dichalcogenide Monolayers
- High Performance Field-Effect Transistor Based on Multilayer Tungsten Disulfide
- Observation of exciton redshift-blueshift crossover in monolayer WS2
- Time-resolved Raman Spectroscopy of Optical Phonons in Graphite: Phonon Anharmonic Coupling and Anomalous Stiffening
- Splitting of the monolayer out-of-plane A'1 Raman mode in few-layer WS2
- Dark excitons and the elusive valley polarization in transition metal dichalcogenides
- Second order resonant Raman scattering in single layer tungsten disulfide (WS)
- Observation of intervalley biexcitonic optical Stark effect in monolayer WS2
- Dark trions and biexcitons in WS2 and WSe2 made bright by e-e scattering
- Strong Valley Zeeman Effect of Dark Excitons in Monolayer Transition Metal Dichalcogenides in a Tilted Magnetic Field
- A tunable time-resolved spontaneous Raman spectroscopy setup for probing ultrafast collective excitation and quasiparticle dynamics in quantum materials
- Dynamical resonance quench and Fano interference in spontaneous Raman scattering from quasiparticle and collective excitations