Creation of Two-Dimensional Electron Gas at the Heterointerface of CaZrO₃/KTaO₃ with Tunable Rashba Spin–Orbit Coupling

Abstract

Compared to SrTiO 3 -based 3d two-dimensional electron gases (2DEGs), KTaO 3 -based 5d 2DEGs have much more exceptional physical properties, such as a higher Curie temperature of spin-polarized 2DEG, higher T c for the 2DEG at superconducting state, and larger spin−orbit coupling. Herein, the CaZrO 3 (CZO) films were deposited on KTaO 3 (001) substrates at the deposition temperature varied from 700 °C to room temperature, and the conductive CZO/KTO interface was obtained at all deposition temperatures. The conductivity of the CZO/KTO heterointerface exhibits critical dependence on the film thickness, where the critical thickness for conduction increases from 3.2 to 6 nm when decreasing the deposition temperature from 700 °C to room temperature. Moreover, the electric properties of the heterointerface grown at room temperature can be modulated strongly by the light illumination. The strength of the spin−orbit coupling exhibits large relative variation with the carrier density. Under the light illumination, the strength of the spin−orbit coupling increases from ∼3.9 × 10 −12 eV m to the maximum of ∼9 × 10 −12 eV m, with the maximal change of the carrier density of only 3 × 10 12 cm −2 . The present work demonstrates an effective tuning of the special 5d-electron-based 2DEGs by light illumination, showing a feasible way for advanced optoelectronic device application.