Exciting the long-lived Higgs mode in superfluid Fermi gases with particle removal

TL;DR

This paper demonstrates how to excite and control long-lived Higgs-mode oscillations in superfluid Fermi gases by particle removal, overcoming previous challenges posed by mode coupling and quasiparticle excitations.

Contribution

It introduces a novel method of exciting persistent Higgs-mode oscillations through particle removal, providing a new experimental approach in superfluid Fermi gases.

Findings

Higgs mode can be excited by modulating scattering length at specific frequencies.

Particle removal at certain momenta produces long-lived Higgs oscillations.

Amplitude of Higgs oscillations can be controlled by the number of particles removed.

Abstract

Experimental evidence of the Higgs mode in strongly interacting superfluid Fermi gases had not been observed until recently [Behrle et al., Nat. Phys. 14, 781 (2018)]. Due to the coupling with other collective modes and quasiparticle excitations, generating stable Higgs-mode oscillations is challenging. We study how to excite long-lived Higgs-mode oscillations in a homogeneous superfluid Fermi gas in the BCS-BEC crossover. We find that the Higgs mode can be excited by time-periodically modulating the scattering length at an appropriate amplitude and frequency. However, even for a modulation frequency below twice the pairing-gap energy, quasiparticles are still excited through the generation of higher harmonics due to nonlinearity in the superfluid. More importantly, we find that persistent Higgs-mode oscillations with almost constant amplitude can be produced by removing particles at an appropriate momentum, and the oscillation amplitude can be controlled by the number of removed particles. Finally, we propose two ways to experimentally realize particle removal.