Tailoring the exciton wave packets in transition-metal dichalcogenide monolayers by using polarized twisted light

Guan-Hao Peng^1*, Oscar Javier Gomez Sanchez¹, Wei-Hua Li¹, Ping-Yuan Lo¹, Shun-Jen Cheng¹

¹Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu, Taiwan

* Presenter:Guan-Hao Peng, email:bnm852i@gmail.com

A twisted light is a spatially structured light that owns a new degree of freedom of quantized orbital angular momentum (OAM) in addition to the spin angular momentum (SAM), i.e., polarization, which is an appealing candidate for new quantum information technology. [1] In this talk, we will present a theoretical study of the photo-excitation of the valley excitons in transition-metal dichalcogenide monolayers (TMD-ML’s) by using polarized Laguerre-Gaussian beams, one of the best-known twisted light’s (TL’s). Our studies show that TL incident on a TMD-ML will lead to the formation of exciton wave packets, [2] being a superposition of finite-momentum exciton states with OAM/SAM encoded geometric patterns over the momentum and position spaces. Moreover, the momentum-dependent optical matrix element (MD-OME) of the exciton wave packet for the exchange-split longitudinal and transverse exciton bands of TMD-ML’s are shown to be highly directional and dependent on the polarization of the applied TL. The MD-OME’s of the wave packet under the linearly polarized TL excitation mimic an exciton multiplexer allowing for selectively detecting the optical signatures of the meV-split longitudinal and transverse exciton bands of TMD-ML’s.




[1] G. F. Quinteiro Rosen, P. I. Tamborenea, and T. Kuhn, Rev. Mod. Phys. 94, 035003 (2022).
[2] G.-H. Peng, O. J. Gomez Sanchez, W.-H. Li, P.-Y. Lo, and S.-J. Cheng, Phys. Rev. B 106, 155304 (2022).

Keywords: twisted light, excitons, transition-metal dichalcogenides, two-dimensional materials