Selective Photoexcitation of Finite-Momentum Exciton in 2D materials via Dielectric Gratings

Jhen-Dong Lin^1,2*, Sheng-Chan Wu^2,3, Till Weickhardt⁴, Vo Khuong Dien¹, Xiao-Fei Wu², Klimmer Sebastian⁴, Giancarlo Soavi⁴, Jer-Shing Huang^1,2,5,6, Shun-Jen Cheng¹

¹Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu, Taiwan
²Leibniz Institute of Photonic Technology, Jena, Germany
³Department of Photonics, National Cheng Kung University, Tainan, Taiwan
⁴Institute of Solid State Physics, Friedrich-Schiller University, Jena, Germany
⁵Abbe Center of Photonics and Institute of Physical Chemistry, Friedrich-Schiller University, Jena, Germany
⁶Research Center for Applied Sciences, Academia Sinica, Taipei, Taiwan

* Presenter:Jhen-Dong Lin, email:jdl.jhendong.lin@gmail.com

Selective excitations via nanostructures, such as gratings [1], local hot spots[2], and metallic tips [3], are widely used in plasmonics. Following a similar methodology and inspiration from recent work [4] utilizing far-field light with orbital angular momentum (OAM) to excite excitons with varying center-of-mass (CoM) momenta in monolayer molybdenum disulfide (MoS₂-ML), we propose to extend this approach using a structured substrate to control CoM momenta of excitons. In this work, we fabricate one-dimensional (1D) gratings with different periodicities on a silicon substrate via focused ion beam (FIB) milling and perform cryogenic photoluminescence (PL) spectroscopy on monolayer molybdenum diselenide (MoSe₂-ML). It is observed that the blue shifts in spectral peak energy with every increment grating periodicity. This spectral shift trend is well accounted for by analysis and theoretical simulations, demonstrating a viable method for selective photoexcitation of finite-momentum excitons using dielectric gratings.

References
[1] Raether, H., Surface Plasmons on Smooth and Rough Surface and on Gratings, Springer (1998).
[2] Arora, A., Dixit, T., Kumar, K. V. A. et al., Plasmon induced brightening of dark exciton in monolayer WSe2 for quantum optoelectronics, Appl. Phys. Lett. 114 (2019).
[3] Park, KD., Jiang, T., Clark, G. et al., Radiative control of dark excitons at room temperature by nano-optical antenna-tip Purcell effect, Nat. Nanotech 13, 59–64 (2018).
[4] Simbulan, K. B., Huang, T.-D., Peng, G.-H. et al., Selective Photoexcitation of Finite-Momentum Excitons in Monolayer MoS2 by Twisted Light, ACS Nano 15, 3481-3489 (2021).

Keywords: Finite-momentum Excitons, 2D materials, Cryogenic Photoluminescence Spectroscopy, Dielectric Grating