Large Rashba Spin-Orbit Effect by Orbital Engineering at SrTiO₃-based Correlated Interfaces

Large spin-orbit effect is an essential element for efficient spin-orbitronics that utilizes the interplay between charge and spin degree of freedom. This spin-orbit effect is generally small in heavy-metal-based or requires large external applied voltages in complex-oxide-based heterostructures. Here, I will firstly discuss lattice and orbital polarization induced at the SrTiO₃-based interfaces. Then, I will present our experimental data to show how Ti-O lattice polarization can be tuned via atomic control of orbital hybridization. This unique approach can present a large Rashba spin-orbit effect at zero applied voltages by interfacial atomic control of orbital hybridization that introduces Ti-O lattice polarization at SrTiO₃-based interfaces. The observed spin-orbit effect (∼3.5×10^-12eV-m) is four-fold larger than that observed in conventional SrTiO₃ interfaces at zero bias voltage. The orbital hybridization and Ti-O polarization are verified through ab-initio electronic structure calculations and high-resolution atomic microscopy. Our results present a unique approach to achieve lattice polarization at SrTiO₃ interfaces and open hitherto unexplored avenues of generating and controlling Rashba spin-orbit effect via orbital engineering to design next-generation spin-orbitronics.