Giant spin-to-charge conversion at an all-epitaxial single-crystal-oxide Rashba interface with a strongly correlated metal interlayer.

Kaneta-Takada, Shingo; Kitamura, Miho; Arai, Shoma; Arai, Takuma; Okano, Ryo; Anh, Le Duc; Endo, Tatsuro; Horiba, Koji et al. · Nat Commun · 2022

basic_science · Level V

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Abstract

The two-dimensional electron gas (2DEG) formed at interfaces between SrTiO<sub>3</sub> (STO) and other oxide insulating layers is promising for use in efficient spin-charge conversion due to the large Rashba spin-orbit interaction (RSOI). However, these insulating layers on STO prevent the propagation of a spin current injected from an adjacent ferromagnetic layer. Moreover, the mechanism of the spin-current flow in these insulating layers is still unexplored. Here, using a strongly correlated polar-metal LaTiO<sub>3+δ</sub> (LTO) interlayer and the 2DEG formed at the LTO/STO interface in an all-epitaxial heterostructure, we demonstrate giant spin-to-charge current conversion efficiencies, up to ~190 nm, using spin-pumping ferromagnetic-resonance voltage measurements. This value is the highest among those reported for all materials, including spin Hall systems. Our results suggest that the strong on-site Coulomb repulsion in LTO and the giant RSOI of LTO/STO may be the key to efficient spin-charge conversion with suppressed spin-flip scattering. Our findings highlight the hidden inherent possibilities of oxide interfaces for spin-orbitronics applications.