Collective Modes in a Unitary Fermi Gas across the Superfluid Phase Transition

TL;DR

This study combines theory and experiment to analyze how collective oscillation frequencies in a unitary Fermi gas vary with temperature, especially near the superfluid transition, revealing new temperature-dependent behaviors.

Contribution

It provides the first experimental evidence of temperature dependence in collective mode frequencies near the superfluid phase transition in a unitary Fermi gas, supported by theoretical calculations.

Findings

Experimental results match theoretical predictions with high accuracy.

Higher nodal excitations show temperature dependence, unlike the lowest axial mode.

First evidence of temperature-dependent collective frequencies near superfluid transition.

Abstract

We provide a joint theoretical and experimental investigation of the temperature dependence of the collective oscillations of first sound nature exhibited by a highly elongated harmonically trapped Fermi gas at unitarity, including the region below the critical temperature for superfluidity. Differently from the lowest axial breathing mode, the hydrodynamic frequencies of the higher nodal excitations show a temperature dependence, which is calculated starting from Landau two-fluid theory and using the available experimental knowledge of the equation of state. The experimental results agree with high accuracy with the predictions of theory and provide the first evidence for the temperature dependence of the collective frequencies near the superfluid phase transition.