  The Peierls-Nabarro barrier is a discrete effect that frequently occurs in
discrete nonlinear systems. A signature of the barrier is the slowing and
eventual stopping of discrete solitary waves. This work examines intense
electromagnetic waves propagating through a periodic honeycomb lattice of
helically-driven waveguides, which serves as a paradigmatic Floquet topological
insulator. Here it is shown that discrete topologically protected edge modes do
not suffer from the typical slowdown associated with the Peierls-Nabarro
barrier. Instead, as a result of their topological nature, the modes always
move forward and redistribute their energy: a narrow (discrete) mode transforms
into a wide effectively continuous mode. On the other hand, a discrete edge
mode that is not topologically protected does eventually slow down and stop
propagating. Topological modes that are initially narrow modes naturally tend
to wide envelope states that are described by a generalized nonlinear
Schrodinger equation. These results provide insight into the nature of
nonlinear topological insulators and their application.
