Anomalous Conductance of a strongly interacting Fermi Gas through a Quantum Point Contact

TL;DR

This paper investigates how strong interactions affect particle conductance in a Fermi gas passing through a quantum point contact, revealing reduced fermionic conductance and enhanced bosonic conductance near the superfluid transition.

Contribution

It introduces a two-channel model and Keldysh formalism to analyze both fermionic and bosonic contributions to conductance in a strongly interacting Fermi gas.

Findings

Fermionic conductance is reduced by interactions compared to the non-interacting case.

Bosonic conductance shows a non-universal plateau exceeding quantized values.

Enhanced conductance is linked to bosonic molecules and low-dimensional effects.

Abstract

In this work we study the particle conductance of a strongly interacting Fermi gas through a quantum point contact. With an atom-molecule two-channel model, we compute the contribution to particle conductance by both the fermionic atoms and the bosonic molecules using the Keldysh formalism. Focusing on the regime above the Fermi superfluid transition temperature, we find that the fermionic contribution to the conductance is reduced by interaction compared with the quantized value for the non-interacting case; while the bosonic contribution to the conductance exhibits a plateau with non-universal values that is larger than the quantized conductance. This feature is particularly profound at temperature close to the superfluid transition. We emphasize that the enhanced conductance arises because of the bosonic nature of closed channel molecules and the low-dimensionality of the quantum point contact.