Electrically manipulating electron spins based on Rashba-type spin-orbit interaction (SOI) is a key pathway for applications of spintronics and spin-based quantum computing. Two-dimensional electronic system (2DES) is a particularly important SOI platform, where the in-plane spin polarization can be tuned with an electric field perpendicular to the 2DES. Spin-orbit interaction (SOI) is a relativistic effect originating from the coupling of a particle's spin s and momentum p under an external electric field E, as described by the SOI Hamiltonian HSO = –μBσ﹒(p×E/2mc2). In the absence of inversion symmetry, SOI lifts the spin degeneracy of electronic states at generic k-points in momentum space, leading to novel effects such as spin/valley Hall effect, spin-galvanic effect, and spin-ballistic transport. As is evident from HSO, the strength of the effective magnetic field Beff = p×E/2mc2 together with the resulting spin polarization is crucially dependent on both p and E and their relative directions. In practice, spin polarization can be regulated with a noncentrosymmetric potential well produced at the interface of semiconducting heterostructures by applying an external electric field, as conceptually demonstrated by the electric manipulation of electron spins in Datta-Das spin-transistors and experimentally exemplified in many 2DESs such as the InGaAs/InAlAs and LaAlO3/SrTiO3 heterostructures.
Taking the advantage of large local electric field (50MV/cm) at EDL interfaces, spin-orbit interaction (SOI) and resulting spin splitting of energy band of 2D systems can be regulated with structure inversion asymmetry (SIA) originated from the interfacial band bending and large applied electric fields, and further be used for generating spin-polarized carriers in solids. We are interested in field-effect-tuning of the SOI and the resulting spin polarization and spin current generation in those transition-metal chalcogenide/oxide systems which have heavy 4d/5d elements with strong atomic SOI and might provide a unique way to extend functionalities of novel spintronics and valleytronics devices.