Transient Holographic Imaging of Spin Magnetic Moments in Perovskites

Hybrid metal halide perovskites have shown to be a promising class of materials for a variety of applications ranging from LEDs [1] to solar cells [2] due to their high quantum efficiency and tunability in the visible range. Compared to conventional semiconductors, perovskites exhibit strong spin-orbit coupling and spin-split Rashba bands, which allow an efficient optical spin manipulation and could possibly extend the spin life-time of excitons. These features are particularly attractive for opto-spintronic applications and data storage [3].<br/>A preliminary step towards the integration of perovskites in opto-spintronic devices is the time- and space-resolved optical study of their magnetic properties. In the present work, we study the spatio-temporal spin dynamics of Methylammonium Lead Tribromide (MAPbBr₃) by the unique combination of two spectroscopic methods: Faraday rotation spectroscopy and Ultrafast Holographic Transient microscopy (UHT) [4]. With our technique we get access to the polarization dependent carrier population as well as the Faraday angle, which is a measure for the spin-aligned magnetic moment. The UTH microscope, which works as a shot-noise limited, all-optical lock-in amplifier, has no upper limitations in the signal repetition rate and can resolve femtosecond dynamics with a sub-micrometre spatial resolution.<br/>By spatially mapping the transient Faraday angle at different temperatures and fluences, we are hence able to investigate the evolution of optically spin-polarized excitons in time and space and identify the dominating spin relaxation mechanisms. This information is essential for the optimization of the materials’ properties and the future realization of opto-spintronic systems.<br/><br/><br/>References<br/>[1] Z. Tan et al., Bright light-emitting diodes based on organometal halide perovskite, Nature Nanotechnology volume 9, pages 687–692 (2014).<br/>[2] L. M. Pazos-Outón et al., Photon recycling in lead iodide perovskite solar cells, Science, Vol 351, Issue 6280 (2016).<br/>[3] A. Privitera et al., Perspectives of Organic and Perovskite-Based Spintronics, Adv. Optical Mater., 9, 2100215 (2021).<br/>[4] M. Liebel et al., Ultrafast Transient Holographic Microscopy, Nano Letters 21 (4), 1666-1671 (2021).