In conventional ferroelectric materials, polarization is an intrinsic property limited by bulk crystallographic structure and symmetry. Recently, it has been demonstrated that polar order can also be accessed using inherently non-polar van der Waals materials through layer-by-layer assembly into heterostructures, wherein interfacial interactions can generate spontaneous, switchable polarization. Here we show that deliberate interlayer rotations in multilayer van der Waals heterostructures modulate both the spatial ordering and switching dynamics of polar domains. The engendered tunability is unparalleled in conventional bulk ferroelectrics or polar bilayers. By means of operando transmission electron microscopy we show how alterations of the relative rotations of three WSe₂ layers produce structural polytypes with distinct arrangements of polar domains with either a global or localized switching response. Furthermore, the presence of uniaxial strain generates structural anisotropy that yields a range of switching behaviours, coercivities and even tunable biased responses. We also provide evidence of mechanical coupling between the two interfaces of the trilayer, a key consideration for the control of switching dynamics in polar multilayer structures more broadly.

在传统的铁电材料中，极化是受块体晶体结构和对称性限制的固有属性。最近，已经证明，使用本质上非极性的范德华材料也可以通过逐层组装成异质结构来获得极性顺序，其中界面相互作用可以产生自发的、可切换的极化。在这里，我们证明多层范德华异质结构中有意的层间旋转可以调节极域的空间排序和切换动力学。所产生的可调谐性在传统的体铁电体或极性双层中是无与伦比的。通过操作透射电子显微镜，我们展示了三个 WSe ₂层相对旋转的改变如何产生具有不同极性域排列的结构多型体，并具有全局或局部切换响应。此外，单轴应变的存在会产生结构各向异性，从而产生一系列开关行为、矫顽力甚至可调的偏置响应。我们还提供了三层的两个界面之间的机械耦合的证据，这是更广泛地控制极性多层结构中的切换动力学的关键考虑因素。