While classical spintronics relies on the use of ferromagnetic materials to generate and detect spin currents, spin-orbitronics exploits the spin-orbit coupling (SOC) in non-magnetic systems to reach this goal. An efficient spin current detection and generation has been achieved in heavy metals such as Pt, W or Ta thanks spin to charge interconversion due to the Spin Hall Effect. However, an even larger interconversion was made possible by the use of the Direct and Inverse Edelstein Effect (EE and IEE) in systems with broken inversion symmetry at interfaces, inducing Rashba SOC.
We observed the IEE in an in interfaces-engineered high-carrier-density SrTiO3 two-dimensional electron gas (2DEG) by mean of SP-FMR. This interconversion can be modulated by the application of a gate voltage, reaching very high values thanks to the enhanced Rashba splitting due to orbital mixing, and the vicinity of the 2DEG Fermi level with an of avoided band crossing with topologically non-trivial order .
By combining this high interconversion efficiency with induced ferroelectric properties in SrTiO3, we show that it is possible to control the sign of the spin to charge interconversion in a non-volatile fashion by manipulating the spin orbit properties of the 2DEG through an electric control of the polarization direction .
This electrically controlled non-volatile interconversion sign switching opens the way to ultra-low power spintronics, in which non-volatility would be provided by ferroelectricity rather than by ferromagnetism.
While classical spintronics has traditionally relied on ferromagnetic metals as spin generators and spin detectors, spin-orbitronics exploits the interplay between charge and spin currents enabled by the spin-orbit coupling (SOC) in non-magnetic systems. An efficient spin-charge interconversion can be obtained through Spin Hall Effect and Inverse Spin Hall Effect in heavy metals such as Pt or Ta. Yet a more efficient conversion can be obtained by exploiting the direct and inverse Edelstein effects at interfaces where broken inversion symmetry induces a Rashba SOC. Although the simple Rashba picture of split parabolic bands is usually used to interpret such experiments, it fails to explain the largest conversion effects and their relation to the actual band-structure. Here, we demonstrate a giant spin-to-charge conversion effect by means of Spin Pumping FMR in an interface-engineered high-carrier-density SrTiO3 two-dimensional electron gas. We use angle-resolved photoemission and Boltzmann calculations to map its peculiar gate dependence. We show that the conversion process is amplified by enhanced Rashba-like splitting due to orbital mixing, and in the vicinity of avoided band crossings with topologically non-trivial order. Our results indicate that oxide 2DEGs are strong candidates for spin-based information readout in novel memory and transistor designs. In parallel, they confirm the promise of topology as a new ingredient to expand the scope of complex oxides for spintronics.