Probing two Higgs oscillations in a one-dimensional Fermi superfluid with Raman-type spin-orbit coupling

TL;DR

This paper theoretically demonstrates the existence of two distinct Higgs oscillations in a one-dimensional spin-orbit-coupled Fermi superfluid, revealing new dynamical features compared to conventional superfluids.

Contribution

It introduces the concept of dual Higgs oscillations in a spin-orbit-coupled Fermi superfluid and links their periods to the minima of the quasi-particle spectrum.

Findings

Two Higgs oscillations observed after Zeeman field changes

Oscillation periods match theoretical predictions based on quasi-particle spectrum

Verification of dual oscillations using periodic ramp strategy

Abstract

We theoretically investigate the Higgs oscillation in a one-dimensional Raman-type spin-orbit-coupled Fermi superfluid with the time-dependent Bogoliubov-de Gennes equations. By linearly ramping or abruptly changing the effective Zeeman field in both the Bardeen-Cooper-Schrieffer state and the topological superfluid state, we find the amplitude of the order parameter exhibits an oscillating behaviour over time with two different frequencies (i.e., two Higgs oscillations) in contrast to the single one in a conventional Fermi superfluid. The observed period of oscillations has a great agreement with the one calculated using the previous prediction [Volkov and Kogan, J. Exp. Theor. Phys. 38, 1018 (1974)], where the oscillating periods are now determined by the minimums of two quasi-particle spectrum in this system. We further verify the existence of two Higgs oscillations using a periodic ramp strategy with theoretically calculated driving frequency. Our predictions would be useful for further theoretical and experimental studies of these Higgs oscillations in spin-orbit-coupled systems.