涡旋光束瞬态吸收显微术解析二维钙钛矿中超快自由激子和声子扩散
Vortex-Beam Transient Absorption Microspectroscopy Resolves Ultrafast Free-Exciton and Polaron Diffusion in 2D Perovskites
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中文总结 AI 辅助
研究利用涡旋光束瞬态吸收显微术平台VTAM，通过编码空间扩散信息到泵浦探测信号，以亚皮秒时间分辨率解析二维钙钛矿超快载流子输运动力学，推导扩散模型并提取相关参数，为研究钙钛矿等半导体系统载流子输运提供强大无成像平台。
中文摘要 AI 辅助
二维Ruddlesden Popper钙钛矿是具有强受限激子特性的有前景的光电子材料。传统瞬态吸收显微镜在探测其超快载流子输运动力学方面存在挑战。本文展示了基于涡旋光束的瞬态吸收显微术平台（VTAM），通过将空间扩散信息编码到模式相关的泵浦探测信号中实现对载流子输运的无成像测量。利用不同拓扑电荷的涡旋探针，VTAM以亚皮秒时间分辨率提供对激子动力学的模式选择性空间灵敏度。通过VTAM解析了快速自由激子扩散及随后向较慢稳态输运的弛豫过程，推导了时间相关扩散模型，给出了瞬态扩散增强、稳态扩散系数等参数。在激子 - 极化子共振处测量揭示了晶格耦合极化子输运中强烈抑制的扩散。这些参数无需空间扫描或图像重建即可提取，确立了VTAM作为研究钙钛矿及其他半导体系统中载流子输运的强大无成像平台。
英文摘要
Two-dimensional (2D) Ruddlesden Popper perovskites are promising optoelectronic materials with strongly confined excitonic properties; however, probing their ultrafast carrier transport dynamics, particularly the initial nonequilibrium diffusion regime, remains challenging because conventional transient absorption microscopy requires complex spatial imaging and lacks sufficient temporal sensitivity to resolve early time diffusion dynamics. Here, we demonstrate a vortex beam based transient absorption microspectroscopy platform (VTAM) enabling imaging free measurement of carrier transport by encoding spatial diffusion information into the mode dependent pump probe signal. By employing vortex probes with different topological charges, VTAM provides mode selective spatial sensitivity to excitonic dynamics with subpicosecond temporal resolution. Using VTAM, we resolved rapid free exciton (FE) diffusion followed by relaxation toward a slower steady state transport regime. A theoretically derived time dependent diffusion model separated transient and steady state transport contributions, yielding a transient diffusion enhancement (68.84 cm2 per s) and a steady state diffusion coefficient (1.85 cm2 per s), thus providing an initial diffusion coefficient (70.69 cm2 per s), and a cooling time of 0.35 ps. Measurements at the exciton-polaron (EP) resonance revealed strongly suppressed diffusion with nearly time independent signal ratios, indicating lattice-coupled EP transport. These parameters were extracted without spatial scanning or image reconstruction, establishing V-TAM as a powerful imaging free platform for investigating carrier transport in perovskites and other semiconductor systems.
