2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/127587Negative differential conductivity is reported for the far from equilibrium quantum spin transport in the insulating regime (J_x < J_z) of finite Heisenberg XXZ spin 1/2 chains. The phenomenon is reproduced analytically for small chains of N=4 spins and further analyzed numerically, for up to N=16, using an efficient pure-state simulation with stochastic spin baths.Unpublished notes, written up in February 2004, 5 pages with 3 .eps figuresQuantum PhysicsStatistical Mechanicstext