Nonequilibrium spectral functions from multiterminal steady-state density functional theory

Multiterminal transport setups allow one to realize measurements and functionalities (e.g., transistors) of nanoscale systems that are more complex than those of the simple two-terminal arrangement. Here the steady-state density functional formalism (i-DFT) for the description of transport through nanoscale junctions with an arbitrary number of leads is developed. In a three-terminal setup and in the ideal STM limit where one of the electrodes (the "STM tip") is effectively decoupled from the junction, the formalism allows one to extract its nonequilibrium spectral function (at arbitrary temperature) while a bias is applied between the other two electrodes. Multiterminal i-DFT is shown to be capable of describing the splitting of the Kondo resonance in an Anderson impurity in the presence of an applied bias voltage, as predicted by numerically exact many-body approaches.