  People have been familiar with the phenomenon of wave refraction for several
centuries. Recently, a novel type of refraction, i.e., negative refraction,
where both incident and refractory lines locate on the same side of the normal
line, has been predicted and realized in the context of linear optics in the
presence of both right- and left-handed materials. In this work, we reveal, by
theoretical prediction and numerical verification, negative refraction in
nonlinear oscillatory systems. We demonstrate that unlike what happens in
linear optics, negative refraction of nonlinear waves does not depend on the
presence of the special left-handed material, but depends on suitable physical
condition. Namely, this phenomenon can be observed in wide range of oscillatory
media under the Hopf bifurcation condition. The complex Ginzburg-Landau
equation and a chemical reaction-diffusion model are used to demonstrate the
feasibility of this nonlinear negative refraction behavior in practice.

Other Condensed Matter;Materials Science