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Seminar | Materials Science Seminar | Materials Science Division

Unraveling the Giant Rashba Effect in Hybrid Metal Halides

MSD Seminar

bstract: The Rashba splitting state — a prototypical quantum phenomenon — causes the splitting of a doubly spin-degenerate band into two spin sub-bands shifted with respect to each other in k space by k0. The formation of the Rashba state exhibits a myriad of rich physical phenomenon and novel spin-dependent functionalities that is essential to spintronics, an enabler of future quantum information technology. Hybrid metal halides (HMHs) are a new class of synthetic semiconductors prepared by low-temperature solution processing with a large chemical and structure universe,” given the synthetic versatility of their molecular cations. While the family of HMHs has shown remarkable performance in photovoltaic and optoelectronic applications, their rich spintronic functionalities have yet to be fully utilized. Particularly because of their large spin-orbit coupling induced by the heavy metal and halogen atoms, HMHs are prime candidates to explore the Rashba splitting state for an efficient charge-to-spin interconversion, which, however, has not been demonstrated to date, probably because of the misleading concept that the reduced order via cruder solution processing would create unintentional defects and diminish the Rashba state. 

Here we report the successful observation of the inverse Rashba-Edelstein effect (IREE) in a prototypical 3-D HMH material (CH3NH3PbBr3), polycrystalline thin films, and single crystals, driven by spin-pumping from a Ni80Fe20 (NiFe) ferromagnetic substrate. We found a large surface-dominated IREE spin-to-charge conversion efficiency, which we separate from the bulk-dominated inverse spin Hall effect by varying the layer thickness. The obtained spin-to-charge conversion efficiency and the Rashba coefficient is comparable with that observed in more traditional Rashba-type systems (e.g., Bi/Ag). Considering that HMH materials are grown from solution, our findings demonstrate a substantial advance toward low-cost, low-temperature processable HMH-based spintronics applications.