Effective bias and potentials in steady-state quantum transport: A NEGF reverse-engineering study

Abstract

Using non-equilibrium Green's functions combined with many-body perturbation theory, we have calculated steady-state densities and currents through short interacting chains subject to a finite electric bias. By using a steady-state reverse-engineering procedure, the effective potential and bias which reproduce such densities and currents in a non-interacting system have been determined. The role of the effective bias is characterised with the aid of the so-called exchange-correlation bias, recently introduced in a steady-state density-functionaltheory formulation for partitioned systems. We find that the effective bias (or, equivalently, the exchange-correlation bias) depends strongly on the interaction strength and the length of the central (chain) region. Moreover, it is rather sensitive to the level of many-body approximation used. Our study shows the importance of the effective/exchange-correlation bias out of equilibrium, thereby offering hints on how to improve the description of densityfunctional-theory based approaches to quantum transport.

Disorder and interactions in systems out of equilibrium: The exact independent-particle picture from density functional theory

“…However, I U =6 < I U =0 , even if the effective energy landscape is smoother. This is due to b eff , that at U = 6 is much smaller than b 40,41,74 .…”

“…Thus, the KS system is described exactly by steady-state NEGF. Further, (v) ij ≡ δ ij v i,eff and b α ≡ b eff,α are found iteratively to make the KS and MB density and current the same 41 . The same iteration protocol as for the quantum rings was used, Eq.…”

“…To assess disorder screening for conductance and currents, we consider out-of-equilibrium systems. In extending DFT to non-equilibrium, we also have to include the notion of an effective bias [39][40][41] .…”

A v0-representability issue in lattice ensemble-DFT and its signature in lattice TDDFT

“…Lattice (TD)DFT approaches have been used in quantum transport for the conductance limit [47], Coulomb Blockade [48,49], Kondo physics [49][50][51], superconducting leads [40], the role of the XC bias in the leads [52,53], single-electron tunneling devices [54], and the competition of disorder and interactions [55,56]. Other uses include ultracold atoms in optical lattices [57][58][59], surface physics [60], entanglement of fermion systems [61] and quantum thermodynamics [62].…”

“…A closer look at v KS -An important outcome of many of these studies is information about the exact XC lattice potential, found via reverse engineering. Under the term "reverse engineering" go a number of approaches [36,38,39,45,52,53,56,[63][64][65][66][67][68][69] which, by using a reference many-body calculation and then numerically reproducing the many-body density within the suitable KS scheme, numerically determine the v KS . In this way, many nontrivial features of the static and time dependent KS potential, e.g.…”