Tunable Couplings of Photons with Bright and Dark Excitons in Monolayer Semiconductors on Plasmonic-Nanosphere-on-Mirror Cavities
Tunable Couplings of Photons with Bright and Dark Excitons in Monolayer Semiconductors on Plasmonic-Nanosphere-on-Mirror Cavities
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DOI：
10.1021/acs.jpcc.3c01019
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发表时间：
2023-05
期刊：
影响因子：
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通讯作者：
Jie Fang;Suichu Huang;Kan Yao;Tianyi Zhang;Mauricio Terrones;Wentao Huang;Yunlu Pan;Yuebing Zheng-Yuebing
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文献类型：
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作者：
Jie Fang;Suichu Huang;Kan Yao;Tianyi Zhang;Mauricio Terrones;Wentao Huang;Yunlu Pan;Yuebing Zheng-Yuebing
可调谐激子-光子耦合对于腔量子电动力学（QED）、极化子化学、光学计算和玻色子激光产生非常重要。在这方面，过渡金属二硫属化物（TMD）中的二维（2D）激子引起了人们的极大兴趣——巨大的振荡器强度赋予了对光学模式的敏感响应，并且它们的激子特性可以通过外部刺激主动调节。然而，单层TMD中自旋禁激暗激子的可调谐耦合很少被证明，并且亮/暗激子-光子耦合如何在一个系统中共存仍然是一个谜。在此，我们利用镜上金纳米球腔中的波导和天线模式分别同时匹配单层 WS2 中亮激子和暗激子的面内和面外偶极矩。在室温下观察到耦合强度高达 60 meV 的强亮激子-光子耦合。我们表明，可以通过控制间隔物厚度来调节波导模式的波长，并证明极化激元的防交叉特征。接下来，通过增加激发角，我们动态地放大了与暗激子耦合的天线模式的相对贡献，并抑制了与亮态耦合的波导模式。此外，由于在强暗激子-光子耦合下主要暗激子衰变引起的均匀展宽受到抑制，因此实现了可调谐的亮激子线宽。这不仅是暗激子可调谐耦合的证明，也是一个富有洞察力的发现，揭示了单个光学腔中亮激子和暗激子光子混合体之间的新颖相互作用，为可调谐 QED 开辟了新的可能性。
Tunable exciton–photon couplings are of great importance for cavity quantum electrodynamics (QED), polariton chemistry, optical computing, and bosonic lasing. In this regard, two-dimensional (2D) excitons in transition metal dichalcogenides (TMDs) have attracted tremendous interest─the huge oscillator strengths endow sensitive responses to optical modes, and their excitonic properties can be actively tuned by external stimuli. However, tunable coupling with spin-forbidden dark excitons in monolayer TMDs has rarely been demonstrated, and how the bright/dark-exciton–photon couplings coexist in one system is still a mystery. Herein, we utilize waveguide and antenna modes in a gold nanosphere-on-mirror cavity to match the in-plane and out-of-plane dipole moments of bright and dark excitons in monolayer WS2, respectively, and simultaneously. Strong bright-exciton–photon couplings with a coupling strength of up to 60 meV are observed at room temperature. We show that the waveguide mode can be tuned in wavelengths by controlling the spacer thickness and demonstrate the anti-crossing feature of polaritons. Next, by increasing the excitation angle, we dynamically enlarge the relative contribution from the antenna mode coupled with dark excitons and suppress the waveguide mode coupled with bright states. Moreover, a tunable bright exciton linewidth is achieved as a result of suppressed homogeneous broadening caused by the dominant dark exciton decays under strong dark-exciton–photon couplings. This is not only proof of tunable couplings with dark excitons but also an insightful finding that reveals the novel interactions between bright- and dark-exciton–photon hybrids in a single optical cavity, opening new possibilities in tunable QED.