Role of defects and phonons in bandgap dynamics of monolayer WS2 at high carrier densities. (3rd December 2020)

• Record Type: Journal Article
• Authors: Brasington, Alexandra; Golla, Dheeraj; Dave, Arpit; Chen, Bin; Tongay, Sefaattin; Schaibley, John; LeRoy, Brian J; Sandhu, Arvinder
• Is Part Of: JPhys materials. Volume 4:Number 1(2021)
• Publication Date: 2020-12-03
• Subjects: transition metal dichalcogenides -- bandgap renormalization -- ultrafast dynamics; Solid state physics -- Periodicals; Materials science -- Periodicals; 530.41
• DOI: 10.1088/2515-7639/abc13b
• Languages: English
• ISSNs: 2515-7639

Abstract

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.