  Novel classical wave phenomenon analogs of the quantum spin Hall effect are
mostly based on the construction of pseudo-spins. Here we show that the
non-trivial topology of a system can also be realized using orbital angular
momentum through angular-momentum-orbital coupling. The idea is illustrated
with a tight-binding model and experimentally demonstrated with a transmission
line network. We show experimentally that even a very small network cluster
exhibits one-way topological edge states, and their properties can be described
in terms of local Chern numbers. Our work provides a new mechanism to realize
counterparts of the quantum spin Hall effect in classical waves and may offer
insights for other systems.
