Topological Field Theory far from Equilibrium

Understand

The observable properties of topological quantum matter are often described by topological field theories.

• We here demonstrate that this principle extends beyond thermal equilibrium.
• To this end, we construct a model of two-dimensional driven open dynamics with a Chern insulator steady state.
• Within a Keldysh field theory approach, we show that under mild assumptions - particle number conservation and purity of the stationary state - an abelian Chern-Simons theory describes its response to external perturbations.