Effective field theory of the Higgs mode in a two-dimensional dilute Bose gas

TL;DR

This paper uses effective field theory to analyze the Higgs mode in a 2D dilute Bose gas, explaining experimental spectral features and clarifying susceptibility relations.

Contribution

It provides a theoretical framework that accounts for the broad spectral continuum of the Higgs mode and its behavior in the superfluid phase, addressing limitations of the $O(2)$ model.

Findings

Spectral function peak is a soft continuum, not sharp.

Peak broadens and vanishes in the superfluid phase.

Scalar susceptibility equals longitudinal susceptibility.

Abstract

We investigate the spectral function of the Higgs mode in a two dimensional Bose gas, by using the effective field theory in the zero temperature limit. Our approach explains the experimental feature that the peak of the spectral function is a soft continuum rather than a sharp peak, broadened and vanishing in the superfluid phase, which cannot be explained in terms of the $O(2)$ model. We also find that the scalar susceptibility is the same as the longitudinal susceptibility.