Collective modes of Fermi superfluid containing vortices along the BEC-BCS crossover

TL;DR

This paper investigates the low-energy collective excitations of a rotating Fermi superfluid with vortices across the BEC-BCS crossover using hydrodynamic theory, revealing how rotation influences mode frequencies and Landau level occupation.

Contribution

It provides a comprehensive calculation of the transverse excitation spectrum across the BEC-BCS crossover, highlighting the effects of rotation and vortex lattices on collective modes.

Findings

In the fast rotation limit, the molecular BEC reaches the lowest Landau level.

At unitarity and BCS regimes, multiple Landau levels are occupied.

The breathing mode frequency difference diminishes near the trap frequency with increasing rotation.

Abstract

Using the coarse-grain averaged hydrodynamic approach, we calculate all low energy transverse excitation spectrum of a rotating Fermi superfluid containing vortex lattices for all regimes along the BEC-BCS crossover. In the fast rotating regime, the molecular BEC enters into the lowest Landau level, but the superfluid in the unitarity and the BCS regimes occupies many low-lying Landau levels. The difference between the breathing mode frequencies at the BEC and unitarity limit shrinks to zero as the rotation speed approaches the radial trap frequency, in contrast to the finite difference in the non-rotating systems.