Obtaining pure steady states in nonequilibrium quantum systems with strong dissipative couplings

Vladislav Popkov, Carlo Presilla

Published 2015-09-16Version 1

We investigate the conditions under which the non equilibrium steady state of an open quantum system described by a Lindblad master equation becomes pure in the Zeno regime, i.e., for infinitely large dissipative coupling. The criterion we obtain replaces Yamamoto's criterion [Phys. Rev. A 72, 024104 (2005)] formulated for arbitrary coupling strength. Using our criterion, we investigate an open $XXZ$ spin $1/2$ chain driven out of equilibrium by boundary reservoirs targeting different spin orientations. In the Zeno regime we find two families of pure nonequilibrium steady states, both in the critical and gapped $XXZ$ regimes. These solutions correspond to particular values of the anisotropy parameter measuring the spin orientation difference between two consecutive sites. In the thermodynamic limit, the set of parameters corresponding to the existence of pure solutions becomes dense in a subset of anisotropies.