The Massive Goldstone (Higgs) mode in two-dimensional ultracold atomic lattice systems

TL;DR

This paper investigates the detection of the massive Goldstone (Higgs) mode near the superfluid-insulator quantum critical point in 2D ultracold atomic systems, providing theoretical insights and experimental conditions for observing this mode.

Contribution

It offers a detailed numerical analysis of the spectral function of the Higgs mode and proposes experimental strategies to observe it in ultracold atom systems.

Findings

Spectral function calculations match recent experimental results.

Conditions for observing the Higgs mode are formulated.

A method to reduce inhomogeneous broadening is proposed.

Abstract

We discuss how to reveal the massive Goldstone mode, often referred to as the Higgs amplitude mode, near the Superfluid-to-Insulator quantum critical point (QCP) in a system of two-dimensional ultracold bosonic atoms in optical lattices. The spectral function of the amplitude response is obtained by analytic continuation of the kinetic energy correlation function calculated by Monte Carlo methods. Our results enable a direct comparison with the recent experiment [M. Endres, T. Fukuhara, D. Pekker, M. Cheneau, P. Schau{\ss}, C. Gross, E. Demler, S. Kuhr, and I. Bloch, Nature 487, 454-458 (2012)], and demonstrate a good agreement for temperature shifts induced by lattice modulation. Based on our numerical analysis, we formulate the necessary conditions in terms of homogeneity, detuning from the QCP and temperature in order to reveal the massive Goldstone resonance peak in spectral functions experimentally. We also propose to apply a local modulation at the trap center to overcome the inhomogeneous broadening caused by the parabolic trap confinement.