Another publication from Prof. Tony Heinz group with Clark-MXR's Model IMPULSE

Population inversion and giant bandgap renormalization in atomically thin WS₂ layers

Alexey Chernikov, Claudia Ruppert, Heather M. Hill, Albert F. Rigosi & Tony F. Heinz

Nature Photonics 9, 466–470 (2015) doi:10.1038/nphoton.2015.104

Abstract

Control of the optical properties of matter on ultrashort timescales is of both fundamental interest and central importance for applications in photonics. It is desirable to achieve pronounced changes over a broad spectral range using the least possible amount of material. Here, we demonstrate a dramatic change over a spectral range of hundreds of meV on the femtosecond timescale in the optical response of atomically thin two-dimensional crystals of the transition-metal dichalcogenide WS2 following excitation by intense optical pump pulses. Our findings reveal the role of extremely strong Coulomb interactions. At the direct gap, we observe a Mott transition from excitonic states to free carriers, accompanied by a giant bandgap renormalization of approximately 500 meV and the development of population inversion.

A new publication from Prof. Tony Heinz group with Model IMPULSE from Clark-MXR. Please contact us for more information on Model IMPULSE and Model iNOPA. 

Observation of Rapid Exciton–Exciton Annihilation in Monolayer Molybdenum Disulfide

Dezheng Sun, Yi Rao, Georg A. Reider, Gugang Chen, Yumeng You, Louis Brézin, Avetik R. Harutyunyan, and Tony F. Heinz

Monolayer MoS₂ is a direct-gap two-dimensional semiconductor that exhibits strong electron–hole interactions, leading to the formation of stable excitons and trions. Here we report the existence of efficient exciton–exciton annihilation, a four-body interaction, in this material. Exciton–exciton annihilation was identified experimentally in ultrafast transient absorption measurements through the emergence of a decay channel varying quadratically with exciton density. The rate of exciton–exciton annihilation was determined to be (4.3 ± 1.1) × 10^–2 cm²/s at room temperature.

Link to the original paper