Band structure engineering of van der Waals heterostructures using ferroelectric clamped sandwich structures

A novel strategy of band structure engineering of van der Waals heterostructure is proposed using a ferroelectric (FE) clamped sandwich structure from first principles. The validity of the strategy is demonstrated in the sandwich structure of In₂Se₃/bilayer-CrI₃/In₂Se₃ (In₂Se₃/bi-CrI₃/In₂Se₃) made by ferroelectric In₂Se₃ layers and semiconducting bilayer (SB) CrI₃. Four states with different band structures in the FE/SB/FE sandwich structure are obtained by switching the FE polarization in the top and bottom In₂Se₃ layers. Two of the states possess spin-splitting semiconducting band structures with opposite spin channel in conduction bands which are generated from a spin-degenerated band structure of the CrI₃ bilayer, resulting in an electric field controllable and nonvolatile four states spin-field effect transistor. The strategy of using FE layers to engineer band structures and generate spin-splitting semiconducting band structure in van der Waals heterostructure opens a new route in two-dimensional electronics and spintronics.