Photo-magnetization in two-dimensional sliding ferroelectrics

Light–matter interaction is one of the key routes to understanding and manipulating geometric and electronic behaviors of materials, especially two-dimensional materials which are optically accessible owing to their high surface to volume ratio. In the current work, we focus on the recently discovered two-dimensional sliding ferroelectric materials, in which the out-of-plane electric polarization can be switched with a small horizontal translation in one layer. Combining symmetry analysis and first-principles calculations, we predict that light illumination could inject non-equilibrium magnetic moments into the sliding ferroelectrics. Such magnetic moment is composed of both spin and orbital degrees of freedom contributions. We use ZrI2, WTe2, and MoS2 bilayer ferroelectrics to illustrate our theory. Under intermediate light illumination, one can yield non-equilibrium magnetic moments on the order of 0.1–1 μB in these systems, which also depends on the polarization nature of incident light. Furthermore, we show that such photo-injected magnetism changes its sign when the sliding dipole moment switches. This photo-magnetization can be detected by magneto-optical methods (such as Kerr or Faraday effect), which serves as an indicator of sliding ferroelectricity. Hence, one can use an all-optical pump and probe setup to measure and detect the subtle sliding ferroelectric phase.