Giant Tunability of Rashba Splitting at Cation-Exchanged Polar Oxide Interfaces by Selective Orbital Hybrization.

The two-dimensional electron gas (2DEG) at oxide interfaces exhibits extraordinary properties such as 2D superconductivity and ferromagnetism coupled to strongly-correlated electrons in narrow d-bands. In particular, 2DEGs in KTaO 3 (KTO) with 5d t 2g orbitals exhibit larger atomic spin-orbit coupling and crystal-facet-dependent superconductivity absent for 3d 2DEGs in SrTiO 3 (STO). Herein, by tracing the interfacial chemistry, weak anti-localization magneto-transport behavior and electronic structures of (001), (110), and (111) KTO 2DEGs, we discovered unambiguously cation exchange across KTO interfaces. Therefore, the origin of the 2DEGs at KTO based interfaces dramatically different from the electronic reconstruction observed at STO interfaces. More importantly, as the interface polarization grows with the higher order planes in KTO case, the Rashba spin splitting becomes maximal for the superconducting (111) interfaces approximately twice that of the (001) interface. The larger Rashba spin splitting couples strongly to the asymmetric chiral texture of the orbital angular moment, and results mainly from the enhanced inter-orbital hopping of the t 2g bands and more localized wave functions. Our finding has profound implications for the search for topological superconductors as well as the realization of efficient spin-charge interconversion for low-power spin-orbitronics based on (110) and (111) KTO interfaces. This article is protected by copyright. All rights reserved.