Experimental observation of the Higgs amplitude mode in supersolids

Demonstrate the experimental observation of the Higgs amplitude (gapped) collective excitation mode in supersolid phases of ultracold quantum gases and thereby confirm its existence in this setting.

Background

The paper studies collective excitations in dipolar supersolids confined in toroidal traps, identifying first sound, second sound, and Higgs amplitude modes and connecting finite-size trapped spectra to bulk band-structure descriptions. While hydrodynamic theories can capture sound modes, they do not account for gapped amplitude (Higgs) modes.

The authors explicitly note that the Higgs mode has not yet been experimentally observed in any supersolid, highlighting a concrete outstanding experimental challenge. Establishing its observation would validate theoretical predictions regarding amplitude oscillations of the supersolid order parameter and complete the picture of collective modes in supersolids.

References

In addition, hydrodynamic theories, which can identify the two sound modes, are unable to capture gapped modes such as the Higgs mode, which is yet to be observed experimentally in a supersolid.

— Decoupled sound and amplitude modes in trapped dipolar supersolids  (2404.12384 - Hertkorn et al., 2024) in Main text, Introduction