Homogeneous Atomic Fermi Gases

TL;DR

This paper reports the creation and analysis of homogeneous ultracold Fermi gases, observing Fermi surfaces, Pauli blocking, superfluid transitions, and polaronic effects in a uniform potential.

Contribution

It introduces a method to produce homogeneous Fermi gases and directly observes fundamental quantum phenomena in a uniform environment.

Findings

Observation of Fermi surface and Pauli blocking in momentum space

Detection of spatially uniform pair condensates at unitarity

Identification of superfluid transition and polaronic effects via compressibility measurements

Abstract

We report on the creation of homogeneous Fermi gases of ultracold atoms in a uniform potential. In the momentum distribution of a spin-polarized gas, we observe the emergence of the Fermi surface and the saturated occupation of one particle per momentum state. This directly confirms Pauli blocking in momentum space. For the spin-balanced unitary Fermi gas, we observe spatially uniform pair condensates. For thermodynamic measurements, we introduce a hybrid potential that is harmonic in one dimension and uniform in the other two. The spatially resolved compressibility reveals the superfluid transition in a spin-balanced Fermi gas, saturation in a fully polarized Fermi gas, and strong attraction in the polaronic regime of a partially polarized Fermi gas.