Dresden 2020 – scientific programme
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DS: Fachverband Dünne Schichten
DS 16: 2D semiconductors and van der Waals heterostructures III (joint session HL/DS)
DS 16.3: Talk
Tuesday, March 17, 2020, 10:15–10:30, POT 81
Revealing the quantum nature of excitons in encapsulated monolayers by optical dispersion measurements — •Lorenz Maximilian Schneider1, Shanece S. Esdaille2, Daniel A. Rhodes2, Katayun Barmak3, James C. Hone2, and Arash Rahimi-Iman1 — 1Faculty of Physics and Materials Sciences Center, Philipps-Universität Marburg, Marburg, 35032, Germany — 2Department of Mechanical Engineering, Columbia University, New York, NY 10027, USA — 3Department of Applied Physics and Applied Mathematics, Columbia University, New York, NY 10027
The dispersion of excitons in TMDC monolayers has been a topic of several recent theoretical studies and is the base of a true understanding of the physics of such systems. Nonetheless, the theoretical papers have contradicting predictions ranging from the formation of Dirac cones or the formation of a second linear exciton branch around zero in-plane momentum to calculations that just expect ordinary degeneracy-lifted parabolic dispersions. Here, we employ Fourier-space spectroscopy to directly measure the dispersion of the A-exciton in a high-quality h-BN encapsulated monolayer system. A remarkably strong dispersion with 2 meV shifts in within the light cone, respectively an effective mass of 7E-4 me can be deduced. Models based on exchange interaction and exciton–polariton formation due to the large oscillator strength are discussed in order to understand the phenomenon clearly observed in PL and reflection spectra [1]. Futhermore, density and temperature dependent behaviour is presented.
[1] L.M. Schneider et al., Optics Express (in press)