  We present a theoretical model to study the nonlinear optical response of
materials with a low-energy spectrum characterised by strongly tilted, type-II,
Weyl cones in two dimensions, which we call 2D Weyl materials. Our findings
reveal that the tilted nature of the Weyl cones is responsible for the
appearance of even harmonics in the nonlinear signal, as well as its strong
polarisation dependence. We discuss how it is possible to control such
nonlinear response and envision how 2D Weyl materials can be used to realise
novel photonic devices for sensing applications.
