The Lifshitz Transition and Spin–Orbit Coupling of the Optical Tunable YSZ/KTaO ₃ Heterointerface

At the surface or interface of KTaO 3 (KTO), 5d two‐dimensional electron gas (2DEG) with strong atomic spin–orbit coupling could be formed. Herein, the 5d 2DEG is created at the interface between amorphous yttria‐stabilized zirconia (YSZ) overlayers and KTO (001) substrates. The interface is metallic for the temperature range from 300 to 2 K. The critical thickness of the YZS overlayer for the interface conductivity is ≈3.5 nm. As the carrier density increases upon light illumination, i.e., the filling of Fermi level, a Lifshitz transition appears at the critical carrier density of n s ≈3.8 × 10 13 cm −2 . Above which, the conductive electrons start to occupy at the d xz /d yz subbands with the different carrier mobility, and the Hall resistance curves become nonlinear at T < 50 K. The peak value of the spin–orbit coupling was also obtained at the Lifshitz transition, which is ≈9 × 10 −12 eVm. This work has the significance on searching KTO‐based conducting and tunable interfaces with spin–orbit coupling.