Physics of tunneling from a macroscopic perspective

Unlike other treatments of electron tunneling, density-gradient theory provides a macroscopic perspective on this quantum phenomenon that is grounded in Newtonpsilas quintessentially classical 2^nd law. We demonstrate the meaning and legitimacy of this unusual viewpoint through careful comparisons with non-equilibrium Greenpsilas function simulations. The main errors made by the density-gradient approach are shown to arise not from its description of the tunneling but rather from its representation of quantum confinement in the electrodes. A new physical understanding of the ad hoc tunneling boundary conditions used in previous work is also exhibited.