Mahan excitons in room-temperature methylammonium lead bromide perovskites.,Nature Communications

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Mahan excitons in room-temperature methylammonium lead bromide perovskites.
Nature Communications ( IF 14.7 ) Pub Date : 2020-02-12 , DOI: 10.1038/s41467-020-14683-5
Tania Palmieri ₁ , Edoardo Baldini ₁ , Alexander Steinhoff ₂ , Ana Akrap ₃ , Márton Kollár ₄ , Endre Horváth ₄ , László Forró ₄ , Frank Jahnke ₂ , Majed Chergui ₁

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In a seminal paper, Mahan predicted that excitonic bound states can still exist in a semiconductor at electron-hole densities above the insulator-to-metal Mott transition. However, no clear evidence for this exotic quasiparticle, dubbed Mahan exciton, exists to date at room temperature. In this work, we combine ultrafast broadband optical spectroscopy and advanced many-body calculations to reveal that organic-inorganic lead-bromide perovskites host Mahan excitons at room temperature. Persistence of the Wannier exciton peak and the enhancement of the above-bandgap absorption are observed at all achievable photoexcitation densities, well above the Mott density. This is supported by the solution of the semiconductor Bloch equations, which confirms that no sharp transition between the insulating and conductive phase occurs. Our results demonstrate the robustness of the bound states in a regime where exciton dissociation is otherwise expected, and offer promising perspectives in fundamental physics and in room-temperature applications involving high densities of charge carriers.

中文翻译：

室温下甲基铵溴化铅钙钛矿中的Mahan激子。

在一项开创性的论文中，马汉预测，在绝缘体到金属的莫特跃迁以上的电子空穴密度下，激子的束缚态仍将存在于半导体中。然而，迄今为止，在室温下还没有明确的证据证明这种奇特的准粒子称为马汉激子。在这项工作中，我们结合了超快宽带光谱学和先进的多体计算方法，揭示了有机无机溴化铅钙钛矿在室温下能容纳马汉激子。在所有可达到的光激发密度（远高于Mott密度）下，观察到了Wannier激子峰的持久性和上述带隙吸收的增强。半导体Bloch方程的解支持了这一点，该方程确定了绝缘相和导电相之间不会发生急剧过渡。

更新日期：2020-02-12

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