Nature 487, 454–458 (2012)

Physicists at the Large Hadron Collider aren't the only ones seeking the Higgs — Manuel Endres and colleagues are also hot on the trail, albeit using a rather different (cold) approach. Endres et al. are seeking evidence of Higgs modes in a system of ultracold rubidium atoms, held in an optical lattice. Although strides have been made in the past in identifying Higgs-like behaviour in various condensed-matter scenarios, these authors have the advantage of recent progress in the high-resolution imaging of single atoms in optical lattices — and hence have been able to find and study Higgs modes in a two-dimensional superfluid close to the quantum phase transition to a Mott insulating state.

Spontaneous symmetry breaking (of U(1) symmetry) in the ordered superfluid, leads to the emergence of a Higgs mode, which is related to amplitude-variation of the complex order parameter for the dynamics close to the order–disorder transition. By carefully tracking the spectral response of the ultracold atoms, through the transition from superfluid to Mott insulator, the authors' long-wavelength, low-energy study turns up just the kind of spectral softening that is expected of Higgs modes.