Van der Waals interfaces can be formed by layer stacking without regard to lattice constants or symmetries of individual building blocks. We engineered the symmetry of a van der Waals interface of tungsten selenide and black phosphorus and realized in-plane electronic polarization that led to the emergence of a spontaneous photovoltaic effect. Spontaneous photocurrent was observed along the polar direction and was absent in the direction perpendicular to it. The observed spontaneous photocurrent was explained by a quantum-mechanical shift current that reflects the geometrical and topological electronic nature of this emergent interface. The present results offer a simple guideline for symmetry engineering that is applicable to a variety of van der Waals interfaces.

Van der Waals界面可以通过层堆叠来形成，而无需考虑晶格常数或各个构建块的对称性。我们设计了硒化钨和黑磷的范德华界面的对称性，并实现了面内电子极化，这导致了自发光伏效应的出现。沿极性方向观察到自发的光电流，而在垂直于该方向的方向上却没有。观察到的自发光电流是由量子力学位移电流解释的，该电流反映了此紧急界面的几何和拓扑电子性质。目前的结果为对称工程提供了一条简单的指南，适用于多种范德华界面。