Visualization of Bloch waves and domain walls

Abstract

The theory of wave propagation in periodic structures1 and its major concept, Bloch's theorem, have typically been assigned to the realm of solid-state physics2, but they are now becoming useful in optics3, acoustics4 and hydrodynamics5. Bloch's theorem is constructive and aesthetic, starting from the idea of perfect order and dealing with infinite extended states. But Bloch's solution is unstable against a small amount of disorder.