Bourelle Sean A, Camargo Franco V A, Ghosh Soumen, Neumann Timo, van de Goor Tim W J, Shivanna Ravichandran, Winkler Thomas, Cerullo Giulio, Deschler Felix
Cavendish Laboratory, University of Cambridge, J J Thomson Avenue, Cambridge, CB3 0HE, UK.
Istituto di Fotonica e Nanotecnologie-CNR, Piazza Leonardo da Vinci 32, 20133, Milano, Italy.
Nat Commun. 2022 Jun 9;13(1):3320. doi: 10.1038/s41467-022-30953-w.
One of the open challenges of spintronics is to control the spin relaxation mechanisms. Layered metal-halide perovskites are an emerging class of semiconductors which possess a soft crystal lattice that strongly couples electronic and vibrational states and show promise for spintronic applications. Here, we investigate the impact of such strong coupling on the spin relaxation of excitons in the layered perovskite BAFAPbI using a combination of cryogenic Faraday rotation and transient absorption spectroscopy. We report an unexpected increase of the spin lifetime by two orders of magnitude at 77 K under photoexcitation with photon energy in excess of the exciton absorption peak, and thus demonstrate optical control over the dominant spin relaxation mechanism. We attribute this control to strong coupling between excitons and optically excited phonons, which form polaronic states with reduced electron-hole wave function overlap that protect the exciton spin memory. Our insights highlight the special role of exciton-lattice interactions on the spin physics in the layered perovskites and provide a novel opportunity for optical spin control.
自旋电子学面临的一个公开挑战是控制自旋弛豫机制。层状金属卤化物钙钛矿是一类新兴的半导体，其具有软晶格，能强烈耦合电子态和振动态，并在自旋电子学应用方面展现出前景。在此，我们结合低温法拉第旋转和瞬态吸收光谱，研究了这种强耦合对层状钙钛矿BAFAPbI中激子自旋弛豫的影响。我们报告了在77 K下，当光激发光子能量超过激子吸收峰时，自旋寿命意外增加了两个数量级，从而证明了对主导自旋弛豫机制的光学控制。我们将这种控制归因于激子与光激发声子之间的强耦合，它们形成了极化子态，减少了电子 - 空穴波函数重叠，从而保护了激子自旋记忆。我们的见解突出了激子 - 晶格相互作用在层状钙钛矿自旋物理中的特殊作用，并为光学自旋控制提供了新机会。
