  Complex oxide heterointerfaces and van der Waals heterostructures present two
versatile but intrinsically different platforms for exploring emergent quantum
phenomena and designing new functionalities. The rich opportunity offered by
the synergy between these two classes of materials, however, is yet to be
charted. Here, we report an unconventional nonlinear optical filtering effect
resulting from the interfacial polar alignment between monolayer MoS$_2$ and a
neighboring ferroelectric oxide thin film. The second harmonic generation
response at the heterointerface is either substantially enhanced or almost
entirely quenched by an underlying ferroelectric domain wall depending on its
chirality, and can be further tailored by the polar domains. Unlike the
extensively studied coupling mechanisms driven by charge, spin, and lattice,
the interfacial tailoring effect is solely mediated by the polar symmetry, as
well explained via our density functional theory calculations, pointing to a
new material strategy for the functional design of nanoscale reconfigurable
optical applications.
