Optical Characterization of Monolayer WSe2

From QCLab
Prof. Ki Ju Yee (Chungnam National University)
  • Speaker: Prof. Ki Ju Yee (Chungnam National University)
  • Date: Wednesday, January 22, 2017, at 16:00
  • Place:

Optical properties of two-dimensional transition-metal dichalcogenides are dominated by strong exciton signatures even at room temperature, the feature originating from large exciton binding energy. I will report on the dielectric constants, exciton binding energy, and spin and exciton dynamics in monolayer WSe2.

By simultaneously measuring the transmission and reflection spectra of monolayer WSe2 transferred on quartz, we obtained real and imaginary part of the dielectric constant independently. Transfer matrix method was used to extract dielectric constants from the transmission and reflection. The signals from the band to band transitions as well as the excitonic transitions are identified from the optical dielectric constants.

The dynamics of excitons, spins, and phonons in monolayer WSe2 are characterized with a resolution of 50 fs from the pump-probe experiments with femtosecond pulses. The wavelength-dependent ultrafast Kerr rotation is explained by the spin-polarized exciton generation through the Kramers-Kronig relation. Time-resolved measurement of the lattice vibration is also discussed.