  Using non-equilibrium Green's functions combined with many-body perturbation
theory, we have calculated steady-state densities and currents through short
interacting chains subject to a finite electric bias. By using a steady-state
reverse-engineering procedure, the effective potential and bias which reproduce
such densities and currents in a non-interacting system have been determined.
The role of the effective bias is characterised with the aid of the so-called
exchange-correlation bias, recently introduced in a steady-state
density-functional-theory formulation for partitioned systems. We find that the
effective bias (or, equivalently, the exchange-correlation bias) depends
strongly on the interaction strength and the length of the central (chain)
region. Moreover, it is rather sensitive to the level of many-body
approximation used. Our study shows the importance of the
effective/exchange-correlation bias out of equilibrium, thereby offering hints
on how to improve the description of density-functional-theory based approaches
to quantum transport.
