多层MoS_(2)激子形成过程中多体效应的超快光谱响应研究  

Ultrafast Spectral Response of Many-Body Effects During Exciton Formation in Multilayer MoS_(2)

作　　者：郭森 赵欣 聂兆刚[1] 马琳 张芳腾 赵韦人[1] 李新忠 张家骅[3] 章文春[4] Guo Sen;Zhao Xin;Nie Zhaogang;Ma Lin;Zhang Fangteng;Zhao Weiren;Li Xinzhong;Zhang Jiahua;Zhang Wenchun(School of Physics and Optelectronic Engineering,Gruangdong University of Technology,Guangzhou,Guangdong 510006,China;School of Physics and Engineering,Henan University of Science&Technology,Luoyang,Henan 471023,China;State Key Laboratory of Luminescence and Applications,Changchan Institute of Optics,Fine Mechanics and Phrysics,Chinese Academy of Sciences,Changchwn,Jilin 130033,China;College of Traditional Chinese Medicine,Jiangxri University of Traditional Chinese Medicine,Nanchang,Jiangxi 330004,China)

机构地区：[1]广东工业大学物理与光电工程学院,广东广州510006 [2]河南科技大学物理工程学院,河南洛阳471023 [3]中国科学院长春光学精密机械与物理研究所发光学及应用国家重点实验室,吉林长春130033 [4]江西中医药大学中医学院,江西南昌330004

出　　处：《中国激光》2021年第11期221-231,共11页Chinese Journal of Lasers

基　　金：国家自然科学基金(11774071,11704079,11874125);广州市科技创新发展专项资金(201904010104,201804010451);发光学及应用国家重点实验室开放基金(SKLA-2019-08);广东省珠江人才计划(2017GC010251)。

摘　　要：采用飞秒瞬态吸收光谱技术研究了多层MoS_(2)在K谷最低激子形成过程中的多体效应对激子共振峰的影响及其内在的多体相互作用机制。经飞秒激光激发后,样品的两个激子峰都表现出早期的瞬间红移和后续先快速后迟缓的蓝移过程。早期的红移幅度随激发功率的提高而增大,但随样品温度的升高而减小。后续最低激子形成后的蓝移幅度随激发功率和样品温度的提高而减小。讨论了引起峰值红移的带隙重整化效应和引起蓝移的带填充效应在激子形成过程中的竞争关系,并且采用指数拟合估计了带隙重整化效应和带填充效应的持续时间随激光功率和样品温度的变化趋势。结果显示,引起共振峰红移的带隙重整化效应对激光功率和样品温度的依赖不明显,而引起共振峰蓝移的带填充效应随着激光功率和样品温度的提高而明显弱化,并且表现出明显的延迟效应。研究结果为动态调控二维材料光电响应性能提供了参考。Objective Two-dimensional(2D)transition metal dichalcogenides(TMDs)have attracted significant attention due to their uniquely controllable properties.Their strong excitonic effects dominate the optical and electronic responses in 2D-TMDs.Coulomb interactions among carriers in the exciton formation process give rise to many interesting many-body effects,which affect the exciton resonance energy and subsequent exciton decay.Despite extensive efforts,a detailed discussion of many-body effects during the exciton formation process is still absent.Typically,narrow-band laser excitation was used in previous studies to inject free electron-hole pairs with energy greater than the lowest exciton resonance energy.In contrast,broadband excitation is helpful to exploit the strong exciton absorption and improve the time-resolution in transient experiments.How do multibody effects induced by broadband excitation influence the exciton resonance and exciton formation when high-density carriers are injected?The answer is essential for the understanding of the exciton properties and is helpful to design and control the photoelectric response of 2D-TMDs.Here we report the use of transient absorption spectroscopy with 10 fs time-resolution to address the ultrafast spectral response of many-body effects in the formation of the lowest exciton at the K valley in five-layer MoS_(2).Methods Multilayer MoS_(2) samples were prepared by chemical vapor deposition.In the transient absorption spectrum intensity(△A)measurements,an 800nm pulse(1 kHz,35 fs)output from an amplified Ti:sapphire laser system was first spectrally broadened using self-phase modulation via a hollow core fiber flled with noble gas,and the pulse duration was compressed with a set of chirped mirrors.Then,the 800 nm pulse was used to construct the degenerate pump-probe system[Fig.1(a)].The pulse energies and their polarizations were adjusted by a combination of a half-wave plate and a polarizer.The △A signal was obtained by measuring the differential absorbance change �

关 键 词：光谱学 瞬态吸收 二维硫化钼 多体效应 激子形成 

分 类 号：O433.1[机械工程—光学工程] O472.3[理学—光学]