Verification of universal relations in a strongly interacting Fermi gas

TL;DR

This paper experimentally verifies the Tan relations, universal equations linking microscopic and thermodynamic properties, in a strongly interacting Fermi gas of atoms, confirming their validity across different interaction regimes.

Contribution

It provides the first experimental verification of the Tan relations in a strongly interacting Fermi gas, using multiple measurement techniques.

Findings

Confirmed the validity of Tan relations in a strongly interacting regime.

Measured the fermion momentum distribution and rf spectrum to test theoretical predictions.

Demonstrated the universal nature of relations across different interaction strengths.

Abstract

Many-body fermion systems are important in many branches of physics, including condensed matter, nuclear, and now cold atom physics. In many cases, the interactions between fermions can be approximated by a contact interaction. A recent theoretical advance in the study of these systems is the derivation of a number of exact universal relations that are predicted to be valid for all interaction strengths, temperatures, and spin compositions. These equations, referred to as the Tan relations, relate a microscopic quantity, namely, the amplitude of the high-momentum tail of the fermion momentum distribution, to the thermodynamics of the many-body system. In this work, we provide experimental verification of the Tan relations in a strongly interacting gas of fermionic atoms. Specifically, we measure the fermion momentum distribution using two different techniques, as well as the rf excitation spectrum and determine the effect of interactions on these microscopic probes. We then measure the potential energy and release energy of the trapped gas and test the predicted universal relations.