Conductance reduction without shot noise in quantum wires

We show that a noiseless current is possible in quantum wires with conductance $e^2∕h$. This unusual behavior is found for ultrathin quantum wires where interactions render the conduction electrons effectively impenetrable. The current is carried by electrons of both spin directions. We study charge and spin transport through such a wire when coupled to bulk leads in two exactly solvable limits: a large applied bias and fast spin relaxation.

Figure 1

Hubbard chain with sites $j$ coupled to electron reservoirs $L$ and $R$. The hopping amplitude ${\lambda }_j$ varies along the chain, and there is a repulsive on-site interaction $U$.