Excitons are hydrogen-like bosonic quasiparticles with Bohr radius of nanometer dimension, combining advantages of electrons and photons. Therefore, excitonic functional devices based on TMDC monolayers at room temperature have attracted intense interest in past decades, as they have promising prospects for overcoming the dilemma of response time and integration in the current generation of electron- or/and photon-based systems. Owing to excellent characteristics such as large exciton binding energy, spin-valley polarization coupling, and actively adjustable energy band, the transition metal dichalcogenide (TMDC) monolayers provide a great platform for exciton devices at room temperature. However, ultra-short lifetimes and low carrier mobility for two-dimensional (2D) exciton in TMDC monolayers give rise to extremely low exciton diffusion length. Thus the manipulation of exciton transportation in excitonic devices is still challenging. Up to now, the observed exciton diffusion lengths are far below the theoretical limit. Especially to the monolayer TMDC fabricated by chemical vapor deposition growth and mechanical exfoliation methods, the sample disorders induced by grain boundary, defects and strain are unavoidable, which is critical for understanding exciton transport phenomena in TMDC monolayers. Recently, Assoc. Prof. Pengfei Qi (Institute of Modern Optics, Nankai University), Prof. Zheyu Fang (School of Physics, Peking University) and Prof. Yanglong Hou (College of Engineering, Peking University) of have made progress in the study of exciton dynamics in low-dimensional disordered systems. They investigated the exciton diffusion behavior and nonequilibrium exciton kinetics under phonon scattering and disorder potentials in WSe2 monolayer flake based on the ultrasensitive spectral imaging and femtosecond pump-probe technologies. It is proved that the exciton diffusion and relaxation processes are subjected to the competition between exciton localization in disordered potentials and phonon-exciton scattering. Temperature manipulation can highly optimize the competition to achieve the fold increase of the exciton diffusion coefficient, which is crucial for prolonged exciton transport and thermal management. 
Figure 1 | Phonon-exciton scattering and disorder potential modulated 2D exciton nonequilibrium dynamics. a, Temperature-dependent efficient exciton diffusion coefficient. b, Temperature-dependent ultrafast exciton relaxation signal. c, Physical diagram of Phonon-exciton scattering and disorder potential dominated exciton diffusion. d, Physical diagram of ultrafast exciton relaxation. The study "Phonon Scattering and Exciton Localization: Molding Exciton Flux in Two Dimensional Disorder Energy Landscape" was published on eLight on Sep. 1, 2020. Assoc. Prof. Pengfei Qi of Institute of Modern Optics, Nankai University and PhD Yang Luo of School of Physics, Peking University is the first author, and Prof. Zheyu Fang of School of Physics, Peking University is the corresponding author. Full text Qi, P., Luo, Y., Shi, B. et al. Phonon scattering and exciton localization: molding exciton flux in two dimensional disorder energy landscape. eLight 1, 6 (2021). Media Reports 1. Prof. Xiaoqin Li from the University of Texas at Austin wrote the highlight for this article on Light: Science & Applications: https://doi.org/10.1038/s41377-021-00657-9 
2. Light Publishing group、WeChat Official Account: China Optics http://www.lightpublishing.cn/hostingPage https://mp.weixin.qq.com/s/ld_b_nyF_cHz_0y4rass3A 
3. International Science News Network sponsored by the American Association for the Advancement of Science (AAAS): EurekAlert! https://www.eurekalert.org/news-releases/934098 
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