Collective Modes in a Two-band Superfluid of Ultracold Alkaline-earth Atoms Close to an Orbital Feshbach Resonance

TL;DR

This paper analyzes collective excitations in a two-band superfluid of ultracold alkaline-earth atoms near an orbital Feshbach resonance, revealing the presence of both Anderson-Bogoliubov and Leggett modes and their impact on density response.

Contribution

It demonstrates the existence and detailed behavior of Leggett and Anderson-Bogoliubov modes in a two-band superfluid system near an orbital Feshbach resonance, a novel insight.

Findings

Identification of the Leggett mode in alkaline-earth atom superfluids.

Analysis of the evolution of collective modes near the resonance.

Connection between collective modes and density response signals.

Abstract

We discuss the collective modes in an alkaline-earth Fermi gas close to an orbital Feshbach resonance. Unlike the usual Feshbach resonance, the orbital Feshbach resonance in alkaline-earth atoms realizes a two-band superfluid system where the fermionic nature of both the open and the closed channel has to be taken into account. We show that apart from the usual Anderson-Bogoliubov mode which corresponds to the oscillation of total density, there also appears the long-sought Leggett mode corresponding to the oscillation of relative density between the two channels. The existence of the phonon and the Leggett modes and their evolution are discussed in detail. We show how these collective modes are reflected in the density response of the system.