Signature of cubic and linear Rashba in \(\text{LaAlO}_\text{3}\)/\(\text{KTaO}_\text{3}\) (0 0 1) heterostructure

Abstract

Complex oxide heterostructures, for example, the \(\text{KTaO}_\text{3}\)/\(\text{LaAlO}_\text{3}\) (KTO/LAO) is an archetypal example to explore the emergent properties due to spin-orbit coupling (SOC) in non-magnetic systems. In this study, we report a first-principles investigation of the electronic and spintronics properties at the perfect (0 0 1) interfaces of the \(\text{KTaO}_\text{3}\)/\(\text{LaAlO}_\text{3}\) (KTO/LAO) heterostructure. We find that the \(\text{TaO}_\text{2}^{+}\)/\(\text{LaO}^{+}\) interface is n-type where the electron-like behavior appears from Ta-5\(d_{xy}\) orbital, whereas \(\text{KO}^{-}\)/\(\text{AlO}_\text{2}^{-}\) is p-type interface contributed by O-2(\(p_{y}+p_{z}\)) orbitals. Due to the lack of inversion symmetry associated with both the interfaces, we have found substantial spin splittings in this system in the presence of the SOC. The Rashba spin splitting in n-type interface is contributed by the unoccupied \(d_{xy}\) and \(d_{z^2}\) band of Ta atom, which is cubic in nature. However, the p-type interface demonstrates a combination of the cubic and linear kind of Rashba splitting and are present in \(d_{yz}\)/\(d_{xz}\) and (\(p_{y}+p_{z}\))/(\(p_{x}+p_{y}\)) bands. We have observed that the strength of the spin-orbit coupling is dependent on energy in case of modified linear Rashba. Furthermore, such interface with two dimensional hole gas (2DHG) exhibits a rich platform for spin-orbitronics and opto-spintronics applications due to the presence of circularly polarized photogalvanic effect (CGPE).