Alignment of Polarization against an Electric Field in van der Waals Ferroelectrics

Going against the grain: Normally, the electric polarization of a ferroelectric compound switches to align itself with a sufficiently strong applied field. Here the authors report polarization switching in ferroelectric van der Waals (vdW) crystals that is based on ion migration across the vdW gap. This ionic mechanism is complementary to but fundamentally different from the polarization rotation underpinning the usual picture of ferroelectric switching. These findings change the way we think about materials featuring both ionic and dipolar properties and enable fresh functionality in ultrathin vdW structures, to advance device physics and nanotechnology.