Role of defects and phonons in bandgap dynamics of monolayer WS2 at high carrier densities

Alexandra Brasington, Dheeraj Golla, Arpit Dave, Bin Chen, Sefaattin Tongay, John Schaibley, Brian J. LeRoy, Arvinder Sandhu

Research output: Contribution to journalArticlepeer-review

1 Scopus citations

Abstract

We conduct ultrafast pump-probe spectroscopy in monolayer WS2 at high pump fluences to gain direct insight into interactions between a high density of carriers, defects, and phonons. We find that defects in the lattice play a major role in determining the relaxation dynamics by trapping the photoexcited carriers and acting as non-radiative recombination centers that emit phonons. In the high carrier density regime explored in our experiments, we observe substantial changes in the transient absorbance signal at unexpectedly long-time delays which we attribute to phonon-induced band gap modification. Our probe frequency dependent measurements and modeling indicate a renormalization of the bandgap by up to 23 meV. These results highlight the importance of defects and phonons for optical applications of monolayer transition metal dichalcogenides.

Original languageEnglish (US)
Article number015005
JournalJPhys Materials
Volume4
Issue number1
DOIs
StatePublished - Jan 2021

Keywords

  • Bandgap renormalization
  • Transition metal dichalcogenides
  • Ultrafast dynamics

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Atomic and Molecular Physics, and Optics

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