Boehme Simon C, Nguyen Tan P T, Zhu Chenglian, Cherniukh Ihor, Feld Leon G, Dirin Dmitry N, Bodnarchuk Maryna I, Katan Claudine, Even Jacky, Kovalenko Maksym V, Rainò Gabriele
Institute of Inorganic Chemistry, Department of Chemistry and Applied Biosciences, ETH Zürich, Zürich, Switzerland.
Laboratory for Thin Films and Photovoltaics, Empa-Swiss Federal Laboratories for Materials Science and Technology, Dübendorf, Switzerland.
Nat Photonics. 2025;19(8):864-870. doi: 10.1038/s41566-025-01684-3. Epub 2025 May 21.
The absorption of light via interband optical transitions plays a key role in nature and applied technology, enabling efficient photosynthesis and photovoltaic cells, fast photodetectors or sensitive (quantum) light-matter interfaces. In many such photonic systems, enhancing the light absorption strength would be beneficial for yielding higher device efficiency and enhanced speed or sensitivity. So far, however, cavity-free light absorbers feature poorly engineerable absorption rates, consistent with the notion that the coupling strength between the initial and final states is an intrinsic material parameter. By contrast, greatly enhanced absorption rates had been theoretically predicted for superradiant systems, which feature giant oscillator strength through spatially extended coherent oscillations of the electron polarization. Unlike for emission processes, however, experimental realizations of superradiance in absorption-'superabsorption'-remain sparse and require complicated excited-state engineering approaches. Here we report superabsorption by the time reversal of single-photon superradiance in large CsPbBr perovskite quantum dots. Optical spectroscopy reveals a bandgap absorption that strongly increases with the quantum dot volume, consistent with a giant exciton wavefunction. Configuration-interaction calculations, quantitatively agreeing with the experiment, attribute the observed single-photon superabsorption to strong electron-hole pair-state correlations. The approach brings new opportunities for the development of more efficient optoelectronic devices and quantum light-matter interfaces.
通过带间光跃迁吸收光在自然和应用技术中起着关键作用，它能实现高效的光合作用和光伏电池、快速的光电探测器或灵敏的（量子）光与物质界面。在许多这样的光子系统中，提高光吸收强度将有利于提高器件效率以及提升速度或灵敏度。然而，到目前为止，无腔光吸收体的吸收率难以通过工程手段进行调控，这与初态和末态之间的耦合强度是一个固有材料参数的观点一致。相比之下，理论上预测超辐射系统具有极大提高的吸收率，这种系统通过电子极化的空间扩展相干振荡具有巨大的振子强度。然而，与发射过程不同的是，吸收中的超辐射——“超吸收”——的实验实现仍然很少，并且需要复杂的激发态工程方法。在此，我们报告了在大型CsPbBr钙钛矿量子点中通过单光子超辐射的时间反演实现的超吸收。光谱学揭示了带隙吸收随量子点体积强烈增加，这与巨大的激子波函数一致。组态相互作用计算与实验定量相符，将观察到的单光子超吸收归因于强电子 - 空穴对态相关性。该方法为开发更高效的光电器件和量子光与物质界面带来了新机遇。
