Spin Hall Effect Driven Spin Transport at Two-Dimensional Conducting SrTiO₃ Surface

The field of spintronics now goes beyond the injection and detection of electron spins, and expands and diversifies into new opportunities such as spin-caloritronics of spin and magnon, spin-orbitronics using spin orbital coupling, and spinterface using spin at the material interface. Among them, the behavior of special electron spins (such as those showing the Rashba-Edelstein effect, Spin Galvanic effect, and others), which can only appear in low-dimensional materials and low-dimensional systems, is a very interesting research field. Here we bypass the problem by generating a spin current not through the spin injection from outside but instead through the inherent spin Hall effect, and demonstrate the non-local spin transport. The analysis on the non-local spin voltage, confirmed by the signature of a Larmor spin precession and its length dependence. And this 2D polar conductor may exhibit directional propagation of itinerant electrons, i.e. the rightward and leftward currents differ from each other, when the time-reversal symmetry is further broken by applying a magnetic field. Further, we report nonlocal spin-transport on two-dimensional surface-conducting SrTiO₃ (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.