Observation of the Fermionic Joule-Thomson Effect

TL;DR

This paper reports the experimental observation of the quantum Joule-Thomson effect in ideal and unitary Fermi gases, revealing how quantum statistics and interactions influence temperature changes during rarefaction.

Contribution

It demonstrates the first observation of the quantum Joule-Thomson effect in Fermi gases and analyzes the role of quantum degeneracy and interactions in this thermodynamic process.

Findings

JT heating observed in ideal Fermi gas, stronger at higher degeneracy

Marginal JT heating in unitary Fermi gas due to attractive interactions

Quantum-statistical effects influence temperature dynamics during rarefaction

Abstract

We report the observation of the quantum Joule-Thomson (JT) effect in ideal and unitary Fermi gases. We study the temperature dynamics of these systems while they undergo an energy-per-particle conserving rarefaction. For scale-invariant systems, whose equations of state satisfy the relation $U\propto PV$, this rarefaction conserves the specific enthalpy, which makes it thermodynamically equivalent to a JT throttling process. We observe JT heating in an ideal Fermi gas, stronger at higher quantum degeneracy, a result of the repulsive quantum-statistical `force' arising from Pauli blocking. In a unitary Fermi gas, we observe that the JT heating is marginal in the temperature range $0.2 \lesssim T/T_{\mathrm{F}} \lesssim 0.8 $ as the repulsive quantum-statistical effect is lessened by the attractive interparticle interaction.