  Using the framework of rigorous algebraic quantum statistical mechanics, we
construct the unique nonequilibrium steady state in the isotropic XY chain in
which a sample of arbitrary finite size is coupled by a bond coupling
perturbation of arbitrary strength to two infinitely extended thermal
reservoirs, and we prove that this state is thermodynamically nontrivial.
Moreover, extracting the leading second order contribution to its microscopic
entropy production and deriving its entropy production in the van Hove weak
coupling regime, we prove that, in the mathematically and physically important
XY chain, the van Hove regime reproduces the leading order contribution to the
microscopic regime.
