Yumoto Go, Sekiguchi Fumiya, Hashimoto Ruito, Nakamura Tomoya, Wakamiya Atsushi, Kanemitsu Yoshihiko
Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, Japan.
Sci Adv. 2022 Jul 29;8(30):eabp8135. doi: 10.1126/sciadv.abp8135.
Monitoring of the spatially resolved exciton spin dynamics in two-dimensional semiconductors has revealed the formation of a spatial pattern and long-range transport of the spin-polarized excitons, which holds promise for exciton-based spin-optoelectronic applications. However, the spatial evolution has been restricted to cryogenic temperatures because of the short exciton spin relaxation times at room temperature. Here, we report that two-dimensional halide perovskites can overcome this limitation owing to their relatively long exciton spin relaxation times and substantial exciton-exciton interactions. We demonstrate the emergence of a halo-like spatial profile in spin-polarized exciton population and its ultrafast expansion at room temperature by performing time-resolved Faraday rotation imaging of spin-polarized excitons in two-dimensional perovskite (CHNH)(CHNH)PbI. Exciton-exciton exchange interactions induce density-dependent nonlinear relaxation and ultrafast transport of exciton spins and give rise to a rapidly expanding halo-like spatial pattern. The density-dependent spatial control suggests the potential of using two-dimensional halide perovskites for spin-optoelectronic applications.
对二维半导体中空间分辨激子自旋动力学的监测揭示了自旋极化激子的空间图案形成和长程输运，这为基于激子的自旋光电子应用带来了希望。然而，由于室温下激子自旋弛豫时间较短，空间演化一直局限于低温。在此，我们报告二维卤化物钙钛矿因其相对较长的激子自旋弛豫时间和显著的激子-激子相互作用而能够克服这一限制。通过对二维钙钛矿（CHNH）（CHNH）PbI中自旋极化激子进行时间分辨法拉第旋转成像，我们展示了自旋极化激子群体中类似光晕的空间分布的出现及其在室温下的超快扩展。激子-激子交换相互作用诱导了与密度相关的非线性弛豫和激子自旋的超快输运，并产生了快速扩展的类似光晕的空间图案。这种与密度相关的空间控制表明了使用二维卤化物钙钛矿进行自旋光电子应用的潜力。
