Nonequilibrium spectral functions from multiterminal steady-state density functional theory

Abstract

Multi-terminal transport setups allow to realize more complex measurements and functionalities (e.g., transistors) of nanoscale systems than 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 to extract its non-equilibrium spectral function (at arbitrary temperature) while a bias is applied between the other two electrodes. Multi-terminal 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. arXiv:1905.13070v1 [cond-mat.mes-hall]

Shaping Electronic Flows with Strongly Correlated Physics

“…Experiments on quantum dots are generally well described by models where an impurity couples two baths that are not otherwise connected. − However, there are also cases where impurities are embedded in a nonequilibrium environment and multiple transport channels are present. Perhaps the simplest examples are side-coupled quantum dots − and magnetic break junctions. − More complex examples include scanning tunneling microscopy of magnetic atoms, − small molecules, − and more recently graphene-like nanostructures − and molecular chains. , Finally, junctions comprising strongly correlated nanostructures can be approximately mapped onto embedded impurity models. − In all these cases, a controlled theoretical treatment is challenging because numerical methods able to reliably access the correlated regime of nonequilibrium quantum impurity models are typically either limited in the level of detail in their description of the baths, especially out of equilibrium, or limited in accuracy by the need to go to high perturbation order (see the Supporting Information). As a result, theoretical work focuses on aspects of the weakly correlated regime − or is confined to single- or few-channel correlated transport. − …”

Thermoelectric transport within density functional theory

“…In this section we apply our iq-DFT framework to the SIAM. Due to its simplicity and evident physical interpretation, this model is ideally suited as a first system to explore the new formalism and has been used in many previous works 28,34,35 , both within and outside any DFT setting. The SIAM describes a single interacting impurity (quantum dot) coupled to non-interacting left (L) and right (R) leads.…”

“…Also, in TDDFT the exact xc functional has memory dependence [20][21][22][23][24][25] whereas the i-DFT xc functionals only depends on the steady state values of the densities. Somewhat unexpectedly, i-DFT can also be used to compute many-body spectral functions both in 26,27 and out of equilibrium 28 .…”

Mott metal-insulator transition from steady-state density functional theory

“…In an idealized Scanning Tunneling Microscope (STM) setup where one of the electrodes (i.e. the "STM tip") couples only weakly to the nanoscale junction, the spectral function at frequency ω can be obtained from the differential conductance at bias V = ω [37,43].…”