Dissipatively dressed quasiparticles in boundary-driven integrable spin chains

The nonequilibrium steady state (NESS) of integrable spin chains experiencing strong boundary dissipation is accounted for by introducing quasiparticles with a renormalized—dissipatively dressed—dispersion relation. This allows us to evaluate the spectrum of the NESS in terms of the Bethe Ansatz equations for a related coherent system that has the same set of eigenstates, the so-called dissipation-projected Hamiltonian. We find explicit analytic expressions for the dressed energies of the and models with effective, i.e., induced by the dissipation, diagonal boundary fields, which are <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"> <a:mrow> <a:mi>U</a:mi> <a:mo>(</a:mo> <a:mn>1</a:mn> <a:mo>)</a:mo> </a:mrow> </a:math> invariant, as well as the and models with effective nondiagonal boundary fields. In all cases, the dissipative dressing generates an extra singularity in the dispersion relation, substantially altering the NESS spectrum with respect to the spectrum of the corresponding coherent model.