Observability of Higgs Mode in a system without Lorentz invariance

TL;DR

This paper investigates the observability of the Higgs mode in a BEC-BCS crossover system without Lorentz invariance, demonstrating that the Higgs mode remains detectable at finite temperatures relevant to experiments.

Contribution

It provides a detailed spectral analysis showing the persistence of the Higgs mode in non-Lorentz-invariant regimes and at finite temperatures.

Findings

Sharp Higgs and Goldstone peaks at zero temperature

Spectral weight transfer from Higgs to Goldstone modes across BCS-BEC crossover

Higgs mode remains observable at experimentally accessible temperatures

Abstract

We study the observability of the Higgs mode in BEC-BCS crossover. The observability of Higgs mode is investigated by calculating the spectral weight functions of the amplitude fluctuation below the critical transition temperature. At zero temperature, we find that there are two sharp peaks on the spectral function of the amplitude fluctuation attributed to Goldstone and Higgs modes respectively. As the system goes from BCS to BEC side, there is strong enhancement of spectral weight transfer from the Higgs to Goldstone mode. However, even at the unitary regime where the Lorentz invariance is lost, the sharp feature of Higgs mode still exists. We specifically calculate the finite temperature spectral function of amplitude fluctuation at the unitary regime and show that the Higgs mode is observable at the temperature that present experiments can reach.