The two dimensional O(N) relativistic field theory applied to bosonic condensed matter systems, predicts a massive amplitude mode which is paradigm of the high energy Higgs particle in electroweak theory. The condensed matter Higgs mode is a critical mode, which softens tuned toward a quantum critical transition. We have shown by that it is still visible as a threshold of optical conductivity, and in scalar dynamical susceptibilities, even when coupled to lower energy Goldstone modes.
I review experimental detection of critical Higgs modes in cold atoms on an optical lattice, at the superconducting to insulator transition in granular films, and as a “non-classical” optical mode in solid helium.
