Dynamical vanishing of the order parameter in a confined Bardeen-Cooper-Schrieffer Fermi gas after an interaction quench

TL;DR

This paper numerically investigates the Higgs mode in a confined ultracold Fermi gas after an interaction quench, revealing a dynamical vanishing of the superfluid order parameter and its dependence on system size and geometry.

Contribution

It introduces a microscopic density-matrix approach within the Bogoliubov-de Gennes framework to study the Higgs mode in a three-dimensional confined Fermi gas, highlighting the dynamical vanishing phenomenon.

Findings

Dynamical vanishing of the superfluid order parameter observed.

The trap geometry influences the Higgs mode dynamics.

Condensate fraction signals can reveal the Higgs mode.

Abstract

We present a numerical study of the Higgs mode in an ultracold confined Fermi gas after an interaction quench and find a dynamical vanishing of the superfluid order parameter. Our calculations are done within a microscopic density-matrix approach in the Bogoliubov-de Gennes framework which takes the three-dimensional cigar-shaped confinement explicitly into account. In this framework, we study the amplitude mode of the order parameter after interaction quenches starting on the BCS side of the BEC-BCS crossover close to the transition and ending in the BCS regime. We demonstrate the emergence of a dynamically vanishing superfluid order parameter in the spatiotemporal dynamics in a three-dimensional trap. Further, we show that the signal averaged over the whole trap mirrors the spatiotemporal behavior and allows us to systematically study the effects of the system size and aspect ratio on the observed dynamics. Our analysis enables us to connect the confinement-induced modifications of the dynamics to the pairing properties of the system. Finally, we demonstrate that the signature of the Higgs mode is contained in the dynamical signal of the condensate fraction, which, therefore, might provide a new experimental access to the nonadiabatic regime of the Higgs mode.