Strong enhancement of transport by interaction on contact links

Strong repulsive interactions within a one-dimensional Fermi system in a two-probe configuration normally lead to a reduced off-resonance conductance. We show that if the repulsive interaction extends to the contact regions, a strong increase of the conductance may occur, even for systems where one would expect to find a reduced conductance. An essential ingredient in our calculations is a momentum-space representation of the leads, which allows a high energy resolution. Furthermore, we demonstrate that these results are independent of the high-energy cutoff and that the relevant scale is set by the Fermi velocity.

Figure 1

(Color online) Schematics of the nanostructure extended by real-space sites and attached to momentum-space leads.

Figure 2

(Color online) Conductance versus gate potential for the interacting resonant-level model for a contact hopping of (a) $t^{\prime }=0.01$ and (b) $t^{\prime }=0.03$ and contact interaction ranging from zero to 25. To each set of DMRG data, a Lorentzian of half width $2w$ has been added as a guide to the eye. The leads are described with a cosine band between $\pm 2$ such that the Fermi velocity is $v_F=2$. In contrast to intradot interaction, the contact interaction enhances the conductance and shows a nonmonotonic behavior versus contact interaction.

Figure 3

(Color online) Site occupation $n_d$ of the resonant level and $n_c$ of the real-space sites attached to the level vs the link interaction in the IRLM for $t^{\prime }=0.01$ and two different gate voltages.

Figure 4

(Color online) Conductance versus gate potential for a resonant three site chain. To each set of DMRG results a Lorentzian of half width $2w$ has been added as a guide to the eye. The leads are described by a cosine band between $\pm 2$ such that $v_F=2$. The interdot interaction suppresses the transport while the contact interaction is seen to enhance the transport.

Figure 5

(Color online) Conductance versus gate potential for a single-site nanostructure without particle-hole symmetry with a contact interaction of $V=1.0$ and a contact hopping of $t^{\prime }=0.1$ for a linear band with cutoff parameter $D=1.0$, 2.0, 4.0, and 10.0 and constant Fermi velocity, $v_F=2$. The conductance is independent of the cutoff. The solid line is a fit with a Lorentzian of half width $w=4.7\times {10}^{-2}$.