Coherence and density dynamics of excitons in a single-layer MoS2 reaching the homogeneous limit

Tomasz Jakubczyk, Goutham Nayak, Lorenzo Scarpelli, Wei-Lai Liu, Sudipta Dubey, Nedjma Bendiab, Laëtitia Marty, Takashi Taniguchi, Kenji Watanabe, Francesco Masia, Gilles Nogues, Johann Coraux, Wolfgang Langbein, Julien Renard, Vincent Bouchiat, Jacek Kasprzak*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

25 Citations (Scopus)

Abstract

We measure the coherent nonlinear response of excitons in a single layer of molybdenum disulfide embedded in hexagonal boron nitride, forming a h-BN/MoS2/h-BN heterostructure. Using four-wave mixing microscopy and imaging, we correlate the exciton inhomogeneous broadening with the homogeneous one and population lifetime. We find that the exciton dynamics is governed by microscopic disorder on top of the ideal crystal properties. Analyzing the exciton ultrafast density dynamics using amplitude and phase of the response, we investigate the relaxation pathways of the resonantly driven exciton population. The surface protection via encapsulation provides stable monolayer samples with low disorder, avoiding surface contaminations and the resulting exciton broadening and modifications of the dynamics. We identify areas localized to a few microns where the optical response is totally dominated by homogeneous broadening. Across the sample of tens of micrometers, weak inhomogeneous broadening and strain effects are observed, attributed to the remaining interaction with the h-BN and imperfections in the encapsulation process.

Original languageEnglish
Pages (from-to)3500-3511
Number of pages12
JournalACS Nano
Volume13
Issue number3
DOIs
Publication statusPublished - 26 Mar 2019
Externally publishedYes

Keywords

  • 2D materials and heterostructures
  • coherent nonlinear spectroscopy
  • exciton dephasing and disorder
  • four-wave mixing
  • microscopy
  • MoS₂
  • ultrafast dynamics

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