Anomalous conductances in an ultracold quantum wire

TL;DR

This paper explains anomalous conductance in ultracold gases through a ballistic constriction by proposing multichannel Andreev reflections and superconductivity at the edges, which enhance conductance beyond Landauer predictions.

Contribution

It introduces a novel model involving multichannel Andreev reflections and edge superconductivity to explain conductance anomalies in ultracold quantum wires.

Findings

Quantized conductance increases with strong interactions.

Andreev reflections cause excess conductance.

Spin conductance is suppressed by superconductivity.

Abstract

We analyze the recently measured anomalous transport properties of an ultracold gas through a ballistic constriction [S. Krinner et al., PNAS 201601812 (2016)]. The quantized conductance observed at weak interactions increases several-fold as the gas is made strongly interacting, which cannot be explained by the Landauer theory of single-channel transport. We show that this phenomenon is due to the multichannel Andreev reflections at the edges of the constriction, where the interaction and confinement result in a superconducting state. Andreev processes convert atoms of otherwise reflecting channels into the condensate propagating through the constriction, leading to a significant excess conductance. Furthermore, we find the spin conductance being suppressed by superconductivity; the agreement with experiment provides an additional support for our model.