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

Abstract

Spin accumulation is generated by passing a charge current through a ferromagnetic layer and sensed by other ferromagnetic layers downstream. Pure spin currents can also be generated in which spin currents flow and are detected as a nonlocal resistance in which the charge current is diverted away from the voltage measurement point. Here, we report nonlocal spin-transport on two-dimensional surface-conducting SrTiO 3 (STO) without a ferromagnetic spin-injector via the spin Hall effect (and inverse spin Hall effect). By applying magnetic fields to the Hall bars at different angles to the nonlocal spin-diffusion, we demonstrate an anisotropic spin-signal that is consistent with a Hanle precession of a pure spin current. We extract key transport parameters for surface-conducting STO, including: a spin Hall angle of γ ≈ (0.25 ± 0.05), a spin lifetime of τ ∼ 49 ps, and a spin diffusion length of λ s ≈ (1.23 ± 0.7) μm at 2 K.

Second-order charge and spin transport in LaO/STO system in the presence of cubic Rashba spin orbit couplings

“…The spin accumulation developed in the system is reflected in the hysteresis of the magnetoresistance and anomalous Hall effect curves [35] and the Hall conductivity measured using a Hall bar geometry [36]. The spin currents developed in the system may be measured via non-local measurements of the voltage developed across one pair of transverse arms of a H-shaped Hall bar system due to the inverse spin Hall effect when a fixed charge current is passed through the other pair of transverse arms [13,47], or elucidated from spin pumping measurements in ferromagnetic [48] or electron spin resonance [49] experiments.…”

Enhancement of Spin Polarization in Two-Dimensional Electron Gases at Patterned LaAlO3/SrTiO3 Interfaces

“…Interfacial two-dimensional electron gases (2DEGs) based on insulating oxide SrTiO 3 (STO), especially the paradigm of LaAlO 3 /SrTiO 3 (LAO/STO), have been of tremendous interest since their discovery in 2004, which have evolved into a platform for both fundamental research and potential electronics and spintronics applications . Various emergent phenomena have been observed at STO-based heterointerfaces, such as superconductivity, , quantum oscillations, − Rashba spin–orbit coupling, − spin-to-charge interconversion, ,, giant tunability via multiple external stimuli, − and ferromagnetism − or spin polarization. − Especially, the combination of high mobility and spin polarization endows STO-based heterostructures with prosperous applications in spin-based logic and memory devices. − …”

Enhancement of the Rashba Effect in a Conducting SrTiO3 Surface by MoO3 Capping

“…The strontium titanate SrTiO 3 (STO) is a band insulator yet has been a preferred platform for oxide spintronics, providing two-dimensional electron gas in the form of LaAlO 3 /STO ,,, and Al 2 O 3 /STO , heterostructures and doped STO surfaces. ,− Ion milling on the STO bare surface changes the surface state from insulating to a high-mobility conducting surface by creating oxygen vacancies, which work as electron doping. − This metallic conducting surface is subjected to the Rashba spin–orbit interaction as theoretically expected. − The angle resolved photoemission spectroscopy (ARPES) of the ultraviolet (UV) radiation STO surface states showed band splitting. − The charges to spin conversion and spin galvanic effects were observed in an Ar + irradiation STO conducting surface, confirming the presence of robust Rashba spin–orbit interactions. The nonreciprocal charge transport was also observed in the Ar + -irradiated STO (111) surface at low temperatures, demonstrating the chiral spin texture of the surface states …”