An ideal Josephson junction in an ultracold two-dimensional Fermi gas

TL;DR

This paper reports the creation and analysis of an ideal Josephson junction in a 2D ultracold Fermi gas, demonstrating superfluidity and phase coherence through measurements of Josephson oscillations and critical current.

Contribution

It presents the first realization of a Josephson junction in an ultracold 2D Fermi gas and confirms ideal Josephson behavior in this strongly correlated system.

Findings

Josephson oscillations follow a sinusoidal current-phase relation

Critical current varies across the BEC-BCS crossover

Strong evidence of superfluidity in 2D Fermi gas

Abstract

The role of reduced dimensionality in high temperature superconductors is still under debate. Recently, ultracold atoms have emerged as an ideal model system to study such strongly correlated 2D systems. Here, we report on the realisation of a Josephson junction in an ultracold 2D Fermi gas. We measure the frequency of Josephson oscillations as a function of the phase difference across the junction and find excellent agreement with the sinusoidal current phase relation of an ideal Josephson junction. Furthermore, we determine the critical current of our junction in the crossover from tightly bound molecules to weakly bound Cooper pairs. Our measurements clearly demonstrate phase coherence and provide strong evidence for superfluidity in a strongly interacting 2D Fermi gas.