单层过渡金属二硫化物光致发光中的热激子效应,Natural Sciences

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单层过渡金属二硫化物光致发光中的热激子效应
Natural Sciences ( IF 2.6 ) Pub Date : 2022-11-29 , DOI: 10.1002/ntls.20220035
Ke Xiao ₁ , Ruihuan Duan ₂ , Zheng Liu ₂ , Kenji Watanabe ₃ , Takashi Taniguchi ₄ , Wang Yao ₁ , Xiaodong Cui ₁

Affiliation

为了动量守恒，热激子在二维半导体的光谱学中通常被忽略，因为大多数热激子都在光锥之外。在这封信中，我们详细阐述了热激子对单层二硒化钼 (MoSe ₂) 与光致发光 (PL) 和 PL 激发 (PLE) 光谱。通过激发强度依赖性 PL、温度依赖性 PL 和 PLE 实验与模拟相结合，我们通过实验区分了 PL 光谱中激子温度和晶格温度的影响。得出的结论是，声学声子辅助 PL 解释了 PL 光谱中的非洛伦兹高能尾部，热激子效应对过渡金属二硫化物的线性光学性质具有重要意义。此外，发现有效激子温度比非共振光激发下的晶格温度高几十开尔文。这表明在考虑激子凝聚等与激子相关的量子相现象时，需要仔细考虑激子温度。实验表明，有效激子温度可以通过激发能量来调节。

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Hot exciton effect in photoluminescence of monolayer transition metal dichalcogenide

Hot excitons are usually neglected in optical spectroscopy in two-dimensional semiconductors for the sake of momentum conservation, as the majority of hot excitons are out of light cones. In this letter, we elaborate on the contribution of hot excitons to optical properties of monolayer Molybdenum diselenide (MoSe₂) with photoluminescence (PL) and PL excitation (PLE) spectroscopy. With the excitation-intensity-dependent PL, temperature-dependent PL and PLE experiments combined with the simulations, we experimentally distinguish the influences of the exciton temperature and the lattice temperature in the PL spectrum. It is concluded that the acoustic phonon-assisted PL accounts for the non-Lorentzian high energy tail in the PL spectrum, and the hot exciton effect is significant to linear optical properties of transition metal dichalcogenides. Besides, the effective exciton temperature is found to be several tens of Kelvin higher than the lattice temperature at non-resonant optical excitation. It indicates that the exciton temperature needs to be carefully taken into account when considering the exciton-related quantum phase phenomena such as exciton condensation. It is experimentally demonstrated that the effective exciton temperature can be tuned by excitation energy.

更新日期：2022-11-29

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