Topological insulators (TIs) have emerged as some of the most efficient spin-to-charge convertors because of their correlated spin-momentum locking at helical Dirac surface states. While endeavors have been made to pursue large "charge-to-spin" conversions in novel TI materials using spin-torque-transfer geometries, the reciprocal process "spinto-charge" conversion, characterized by the inverse Edelstein effect length (λ IEE ) in the prototypical TI material (Bi 2 Se 3 ), remains moderate. Here, we demonstrate that, by incorporating a "second" spin-splitting band, namely, a Rashba interface formed by inserting a bismuth interlayer between the ferromagnet and the Bi 2 Se 3 (i.e., ferromagnet/Bi/Bi 2 Se 3 heterostructure), λ IEE shows a pronounced increase (up to 280 pm) compared with that in pure TIs. We found that λ IEE alters as a function of bismuth interlayer thickness, suggesting a new degree of freedom to manipulate λ IEE by engineering the interplay of Rashba and Dirac surface states. Our finding launches a new route for designing TI-and Rashba-type quantum materials for next-generation spintronic applications.

Ferroelectric Rashba semiconductors (FERSCs) have recently attracted intensive attention due to their giant bulk Rashba parameter, α R , which results in a locking between the spin degrees of freedom and the switchable electric polarization. However, the integration of FERSCs into microelectronic devices has provoked questions concerning whether the Rashba effect can persist when the material thickness is reduced to several nanometers. Here we find that α R can keep a large value of 2.12 eV Å in the 5.0 nm thick GeTe film. The behavior of α R with thickness can be expressed by the scaling law and provides a 3D thickness limit of the bulk Rashba effect, d c = 2.1 ± 0.5 nm. Finally, we find that the thickness can modify the Berry curvature as well, which influences the polarization and consequently alters the α R . Our results give insight into understanding the factors influencing α R in FERSCs and pave a novel route for designing Rashba-type quantum materials.

Magnetization promoted activity of magnetic catalysts towards the oxygen evolution reaction (OER) has attracted great attention, but remains a puzzle where the increment comes from. Magnetization of a ferromagnetic material only changes its magnetic domain structure. It does not directly change the spin orientation of unpaired electrons in the material. The confusion is that each magnetic domain is a small magnet and theoretically the spin-polarization promoted OER already occurs on these magnetic domains, and thus the enhancement should have been achieved without magnetization. Here, we demonstrate that the enhancement comes from the disappeared domain wall upon magnetization. Magnetization leads to the evolution of the magnetic domain structure, from a multi-domain one to a single domain one, in which the domain wall disappears. The surface occupied by the domain wall is reformatted into one by a single domain, on which the OER follows the spin-facilitated pathways and thus the overall increment on the electrode occurs. This study fills the missing gap for understanding the spin-polarized OER and it further explains the type of ferromagnetic catalysts which can give increment by magnetization.