Persistent spin grids with spin-orbit coupled 2D electron gas

We consider the diffusive spin dynamics of a 2D electron gas with spin-orbit coupling confined within a grid of narrow channels. We show that the lifetime of certain spin distributions in such grids greatly exceeds that in an unconfined 2D electron gas and diverges as the channel width approaches zero. Such persistent spin grids occur if the electron spin orientation remains invariant after diffusion around the grid plaquette. We establish a topological $\mathbb{Z}_2$ classification for persistent spin grids and speculate that the setup can be used to simulate non-Abelian lattice gauge theories.