Coupling Sliding Ferroelectricity and Shear Strain in Parallel Stacked hBN

Sliding ferroelectricity is a phenomenon seen in certain van der Waals layered materials in which electric polarization reversal is accompanied by a relative shift of adjacent layers. It can be realized by stacking materials in a way that breaks centrosymmetry, as, for example, in twisted or A-A stacked hexagonal boron nitride, but it is also present natively in some acentric materials such as WTe₂. Motivated by the possibility of novel electromechanical coupling and the potential of employing the phenomenon for robust memory applications, we have developed a technique for applying c-axis shear deformation to 2D device structures. We focus here on parallel stacked hBN where the stacking order shifts to metastable A-B or B-A rather than the high energy A-A stacking order, breaking the centrosymmetry found in antiparallel A-A’ hBN. As a dielectric, the ferroelectric hBN layers are incorporated into a dual-gated graphene-based transistor device, and resistivity is measured while shear deformation is applied. This applied shear strain resulted in controllable tuning of the coercive field in hBN. We achieve shifts on the order of 1/10th of the coercive field and observe an additional domain in a device that was not originally accessible with the electric field strength applied.