Conductance through atoms: Dot or channel?

We present a first-principles calculation of the transmission eigenchannels of an Al atomic wire between jellium electrodes. We show how the decomposition of electronic states into eigenchannels can provide a transparent view of electronic transport in atomic-sized systems. In particular, we show how local density of states and current density resolved into eigenchannels reflect the atomic orbitals of the single Al atom. On the other hand, the eigenchannel density of states has a one-dimensional (1D) band character for the straight three-atom wire. From this we conclude that the transport through the single Al atom in this case mainly has a 1D (channel) character in contrast to a zero-dimensional resonant tunneling (dot) character.