Pairing and Phase Separation in a Polarized Fermi Gas

TLDR

These results are relevant to predictions of exotic new phases of quark matter and of strongly magnetized superconductors. We observed pairing in a number‑polarized two‑component Fermi gas, found that beyond a critical polarization the gas separates into a superfluid core surrounded by a normal shell, noted that the critical polarization decreases with weaker attraction, and measured β = 0.54(5) for the universal energy, in agreement with recent theory.

Abstract

We report the observation of a pairing in a number polarized two-component gas of atomic fermions. Beyond a critical polarization, the gas separates into a superfluid paired core surrounded by a shell of normal unpaired fermions. The critical polarization diminishes with decreasing attractive interaction. We also measure the parameter \beta = 0.54 (5) describing the universal energy of a strongly interacting Fermi gas, and find good agreement with most recent theory. These results are relevant to predictions of exotic new phases of quark matter and of strongly magnetized superconductors.