Coupling Sliding Ferroelectricity and Shear Strain in Bilayer WTe₂

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 bilayer WTe₂, which is a natural sliding ferroelectric offering the additional benefit that its conductivity is different in the opposite polarization states, allowing easy detection of the polarization switch. We have performed measurements on customized dual-gated WTe₂ device designs and successfully observed signs of shear-strain modulation of the coercive electric field in them.