Pure Spin Currents Driven by Colossal Spin-Orbit Coupling on Two-Dimensional Surface Conducting SrTiO₃

Area of Science:

• Condensed Matter Physics
• Materials Science
• Spintronics

Background:

• Spin accumulation and pure spin currents are crucial for spintronic devices.
• Traditional methods involve ferromagnetic spin injectors, limiting device integration.
• Two-dimensional electron systems offer novel platforms for spin transport studies.

Purpose of the Study:

• To investigate nonlocal spin transport in two-dimensional surface-conducting SrTiO₃ (STO).
• To explore spin generation and detection without ferromagnetic materials, utilizing the spin Hall effect.
• To characterize spin transport properties in STO, including spin lifetime and diffusion length.

Main Methods:

• Nonlocal spin transport measurements on Hall bars of surface-conducting STO.
• Utilized the spin Hall effect (and inverse spin Hall effect) for spin current generation and detection.
• Applied magnetic fields at various angles to probe spin precession (Hanle effect) and anisotropy.

Main Results:

• Demonstrated nonlocal spin transport in STO without a ferromagnetic spin-injector.
• Observed an anisotropic spin signal, consistent with pure spin current Hanle precession.
• Extracted key parameters: spin Hall angle (γ ≈ 0.25 ± 0.05), spin lifetime (τ ∼ 49 ps), and spin diffusion length (λ_s ≈ 1.23 ± 0.7 μm) at 2 K.

Conclusions:

• Surface-conducting STO is a viable material for nonlocal spin transport via the spin Hall effect.
• The observed anisotropy confirms the presence and behavior of pure spin currents.
• Provides essential transport parameters for advancing STO-based spintronic applications.