Detecting the Amplitude Mode of Strongly Interacting Lattice Bosons by Bragg Scattering

TL;DR

This paper reports the first experimental detection of the Higgs-like amplitude mode in a strongly interacting lattice Bose condensate using Bragg spectroscopy, with theoretical support from dynamic Gutzwiller calculations.

Contribution

It demonstrates the ability to detect the amplitude mode with full momentum resolution beyond linear response in ultracold atomic gases.

Findings

First detection of Higgs-type amplitude mode in lattice bosons

Good quantitative agreement with Gutzwiller calculations

Observation of systematic frequency shifts due to Bragg beam intensity

Abstract

We report the first detection of the Higgs-type amplitude mode using Bragg spectroscopy in a strongly interacting condensate of ultracold atoms in an optical lattice. By the comparison of our experimental data with a spatially resolved, time-dependent dynamic Gutzwiller calculation, we obtain good quantitative agreement. This allows for a clear identification of the amplitude mode, showing that it can be detected with full momentum resolution by going beyond the linear response regime. A systematic shift of the sound and amplitude modes' resonance frequencies due to the finite Bragg beam intensity is observed.