Kardar--Parisi--Zhang density hydrodynamics in a coherent XXZ--ASEP Lindbladian

Abstract

Coherent interactions can generate quantum correlations without changing a stationary density current. Whether that current still determines long-wavelength transport is a dynamical question. We study an XXZ chain with asymmetric Lindblad hopping, whose stationary current has the asymmetric simple exclusion process (ASEP) form although its populations do not evolve autonomously. The current curvature and static susceptibility fix the leading Kardar--Parisi--Zhang (KPZ) length and amplitude without a fitted length or amplitude conversion factor. The density-visible Liouvillian spectrum, real-space spreading, and Fourier relaxation support KPZ scaling at the finite coherent couplings studied. Central and intermediate stationary density correlations are consistent with the Prähofer--Spohn profile at this microscopic scale, with resolved finite-time corrections. Reservoir-matched classical references quantify boundary effects, while symmetric hopping recovers diffusion and reduced asymmetry produces the expected crossover. These results connect an exact nonlinear current to the observed long-wavelength KPZ transport of the physical density in an interacting open quantum chain away from the isotropic Heisenberg point.