Electric-field-tunable intervalley excitons and phonon replicas in bilayer WSe$_2$
Electric-field-tunable intervalley excitons and phonon replicas in bilayer WSe$_2$
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发表时间：
2021-01
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通讯作者：
M. M. Altaiary-M.;Erfu Liu;C. Liang;F. Hsiao;J. V. Baren;T. Taniguchi;Kenji Watanabe;N. Gabor;Yia-Chung Chang;C. Lui
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作者：
M. M. Altaiary-M.;Erfu Liu;C. Liang;F. Hsiao;J. V. Baren;T. Taniguchi;Kenji Watanabe;N. Gabor;Yia-Chung Chang;C. Lui
本文报道了用光致发光直接观察到双分子层WSe2中Q导谷和Γ价谷之间的谷间激子。Τhe QΓ激子比QK激子低~18 meV，主导双分子层WSe2的发光。通过测量门可调谐电场下的激子光谱，揭示了QΓ和QK激子之间不同的层间电偶极矩和Stark位移。值得注意的是，我们可以使用电场在QΓ和QK激子之间切换能量顺序和主导发光。QΓ和QK激子都表现出明显的声子复制，其中由于存在（几乎）共振激子-声子散射和许多双声子散射路径，双声子复制比单声子复制更突出。我们可以通过全面的理论建模和计算来模拟复制光谱。Stark位移和声子副本的理论和实验之间的良好一致性有力地支持了我们对QΓ和QK激子的分配。
We report the direct observation of intervalley exciton between the Q conduction valley and Γ valence valley in bilayer WSe2 by photoluminescence. Τhe QΓ exciton lies at ~18 meV below the QK exciton and dominates the luminescence of bilayer WSe2. By measuring the exciton spectra at gate-tunable electric field, we reveal different interlayer electric dipole moments and Stark shifts between QΓ and QK excitons. Notably, we can use the electric field to switch the energy order and dominant luminescence between QΓ and QK excitons. Both QΓ and QK excitons exhibit pronounced phonon replicas, in which two-phonon replicas outshine the one-phonon replicas due to the existence of (nearly) resonant exciton-phonon scatterings and numerous twophonon scattering paths. We can simulate the replica spectra by comprehensive theoretical modeling and calculations. The good agreement between theory and experiment for the Stark shifts and phonon replicas strongly supports our assignment of QΓ and QK excitons.