Landauer Conductance without Two Chemical Potentials

We present a theory of the four--terminal conductance for the multi-channel tunneling barrier, which is based on the self-consistent solution of Shrodinger, Poisson and continuity equations. We derive new results for the case of a barrier embedded in a long wire with and without disorder. We also recover known expressions for the conductance of the barrier placed into a ballistic constriction. Our approach avoids a problematic use of two chemical potentials in the same system.