  We study the relaxation dynamics of an extended Fermi-Hubbard chain with a
strong Wannier-Stark potential tilt coupled to a bath. When the system is
subjected to dephasing noise, starting from a pure initial state the system's
total von Neumann entropy is found to grow monotonously. The scenario becomes
rather different when the system is coupled to a thermal bath of finite
temperature. Here, for sufficiently large field gradients and initial energies,
the entropy peaks in time and almost reaches its largest possible value
(corresponding to the maximally mixed state), long before the system relaxes to
thermal equilibrium. This entropy peak signals a prethermal memory loss and,
relative to the time where it occurs, the system is found to exhibit a simple
scaling behavior in space and time. By comparing the system's dynamics to that
of a simplified model, the underlying mechanism is found to be related to the
localization property of the Wannier-Stark system, which favors dissipative
coupling between eigenstates that are close in energy.
