The Equation of State of a Low-Temperature Fermi Gas with Tunable Interactions

TL;DR

This paper measures the equation of state of a low-temperature ultracold Fermi gas across various interaction strengths, providing experimental data that benchmark many-body theories and relate to systems like neutron star crusts.

Contribution

It offers the first comprehensive experimental measurement of the equation of state for a tunable ultracold Fermi gas at low temperatures, comparing results with advanced theoretical models.

Findings

Fermi liquid behavior observed in the partially polarized normal phase

Equation of state data agrees with Monte-Carlo and Lee-Huang-Yang theories

Phase diagram reveals the nature of interactions across different regimes

Abstract

Interacting fermions are ubiquitous in nature and understanding their thermodynamics is an important problem. We measure the equation of state of a two-component ultracold Fermi gas for a wide range of interaction strengths at low temperature. A detailed comparison with theories including Monte-Carlo calculations and the Lee-Huang-Yang corrections for low-density bosonic and fermionic superfluids is presented. The low-temperature phase diagram of the spin imbalanced gas reveals Fermi liquid behavior of the partially polarized normal phase for all but the weakest interactions. Our results provide a benchmark for many-body theories and are relevant to other fermionic systems such as the crust of neutron stars.