Sliding ferroelectricity in a bulk misfit layer compound (PbS)${}_{1.18}$VS${}_2$

Twisted heterostructures of two-dimensional crystals can create a moiré landscape, which can change the properties of it’s parent crystals. However, the reproducibility of manual stacking is far from perfect. Here, the alternated stacking of post-transition metal monochalcogenides and transition metal dichalcogenides in misfit layer compound crystals is used as a moiré generator. Using X-ray diffraction, the presence of twins with a well-defined small twist angle between them is shown. Due to the twist, the surface electrical potential from the induced ferroelectricity is observed using scanning probe microscopy and electron microscopy.