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

Abstract

Compared to SrTiO₃-based 3d two-dimensional electron gases (2DEGs), KTaO₃-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 CaZrO₃ (CZO) films were deposited on KTaO₃ (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 × 10¹² 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.