Strongly correlated Fermi superfluid near an orbital Feshbach resonance: Stability, equation of state and Leggett mode

TL;DR

This paper develops a theoretical framework to analyze the stability, equation of state, and collective excitations of a strongly correlated $^{173}$Yb Fermi superfluid near an orbital Feshbach resonance, revealing its metastability and damping of the Leggett mode.

Contribution

The paper introduces a quantitative pair-fluctuation theory within a two-band model for $^{173}$Yb Fermi gases near an orbital Feshbach resonance, analyzing stability and collective modes.

Findings

$^{173}$Yb Fermi gas is intrinsically metastable.

The equation of state is peculiar due to a small positive singlet scattering length.

The Leggett mode is severely damped, with conditions for an undamped mode discussed.

Abstract

We theoretically study the superfluid phase of a strongly correlated $^{173}$Yb Fermi gas near its orbital Feshbach resonance, by developing a quantitative pair-fluctuation theory within a two-band model. We examine the density excitation spectrum of the system and determine a stability phase diagram. We find that the $^{173}$Yb Fermi gas is intrinsically metastable and has a peculiar equation of state, due to the small but positive singlet scattering length. The massive Leggett mode, arising from the fluctuation of the relative phase of two order parameters, is severely damped. We discuss the parameter space where an undamped Leggett mode may exist.