Transport through an interacting system connected to leads

TL;DR

This paper investigates electron transport in an interacting Hubbard system connected to leads using Keldysh formalism, revealing how filling factor and interaction strength influence current and conductance.

Contribution

It provides a detailed numerical analysis of transport properties in Hubbard models, highlighting differences between half-filled and non-half-filled cases, including gap effects and conductance behavior.

Findings

At half-filling, a charge gap suppresses current exponentially with system size and U.

For non-half-filled systems, current remains relatively unaffected by interaction strength and length.

Conductance is more sensitive to filling factor than to interaction U or system length.

Abstract

Keldysh formalism is used to get the current-voltage characteristic of a small system of interacting electrons described by a Hubbard model coupled to metallic wires. The numerical procedure is checked recovering well-known results for an Anderson impurity. When larger interacting regions are considered quite different results are obtained depending on whether the Hubbard part is half-filled or not. At half-filling the existence of a gap charge manifests itself making current exponentially small as a function both of the number of interacting sites and the value of U. The behavior changes at large voltages above the gap energy when activated charge transport takes place. On the contrary, for filling factors other than half, current goes through the interacting system suffering just a small amount of scattering at both connections. Conductance depends slightly on U and much more on the filling factor but not on the length of the interacting region.