Rashba splitting in bilayer transition metal dichalcogenides controlled by electronic ferroelectricity

Abstract

Based on first-principles calculations and $\mathbit{k}\ifmmode\cdot\else\textperiodcentered\fi{}\mathbit{p}$ model analyses, we uncover the coexistence and coupling of Rashba spin splitting with electronic ferroelectricity in bilayer transition metal dichalcogenides $M{X}_{2}$ ($M=\text{Mo,W}$; $X=\text{S,Se,Te}$) with certain stacking configurations. The reversible spontaneous ferroelectric polarization, along the out-of-plane direction (the preferred direction for applications), totally arises from the interlayer charge transfer, rather than being governed by the ionic displacement as found in conventional ferroelectrics. The spin texture related to the Rashba spin splitting can be reversed upon inversion of the ferroelectric polarization. In particular, by applying a small in-plane compressive strain, the magnitude of Rashba band splitting can be tuned to be as large as 100 meV. These results would open up possibilities for exploring two-dimensional multiferroic physics and developing electrically controlled nanoscale spintronic devices.