Using optical signatures of exciton-plasmon coupled states to probe many-body interactions in gated 2D materials

Yia-Chung Chang^1*, Chun Hung Lui²

¹Research Center for Applied Sciences, Academia Sinica, Taipei, Taiwan
²Physics and Astronomy, University of California, Riverside, Riverside, USA

* Presenter:Yia-Chung Chang, email:yiachang@gate.sinica.edu.tw

Some recent studies have been reported on the optical properties of transition-metal dichalcogenides (TMDs) and related moiré structures. Optical spectra (including reflectance and photoluminescence) of gated monolayer and bilayer TMDs can reveal many striking spectral features, which are often puzzling. These unusual spectral features are caused by the strong coupling of excitons with excitations of the Fermi sea of injected free carriers in these systems. We show that using a four-particle model (including the exciton plus an electron-hole pair generated from the Fermi sea) which includes multi-valley band structures and realistic Coulomb interactions can account for these spectral features qualitatively [1-3]. Furthermore, the intriguing Landau oscillation behavior under a magnetic field and complicated multi-path phonon-assisted optical emission features can also be explained [4,5].
[1] Y. C. Chang, S. Shiau, M. Combescot, Phys. Rev. B 98, 235203 (2018)
[2] E. Liu et al., Nature Communications 12:6131 (2021).
[3] E. Liu et al., Nature 594, 46 (2021)
[4] E. Liu et al., Phys. Rev. Lett. 124, 1976802 (2020); Phys. Rev. Lett. 124, 097401 (2020)
[5] M. M. Altaiary et al., Nano Letters, 22, 1829 (2022).

Keywords: 2D materials, exciton-plasmon coupling, transition-metal dichalcogenides, trion