The Higgs Boson-from Superconductors to Supercolliders and back
The 2013 Nobel Prize in physics was awarded to Peter Higgs and Francois Englert "for the theoretical discovery of the mechanism that contributes to our understanding of the origin of mass of subatomic particles". This Nobel committee decision was based on the detection of the predicted "Higgs boson" in the CERN Large Hydron Collider within the framework of the largest experiment ever held by mankind. Obviously, this recent discovery regarding the "God Particle" generated much worldwide interest. But what is less known is that the inspiration for its prediction came from theoretical works in the field of Superconductivity.
Ironically, while the ideas regarding this ‘missing link’ in the Standard Model of elementary particles were stimulated by superconductor theory, the Higgs mode was never clearly observed in superconductors. The main reason for this is the fact that the energy required to excite the Higgs boson, the Higgs mass, is large enough to break cooper-pairs and hence suppress superconductivity. Nevertheless, recent theories show that if the Higgs mass could be softened below the superconducting gap it should be visible in two dimensions. Such conditions can be met by tuning a superconducting film towards a superconductor-insulator quantum phase transition. Indeed, in our experimental study on thin superconducting films for which the superconductor to insulator transition is tuned by disorder, an excess optical spectral weight below the superconducting gap energy was observed and identified as an explicit observation of the Higgs mode in a superconductor.
This experiment closes a historical circle by connecting the Higgs Boson to its theoretical "ancestor" and serves as a beautiful example that the same fundamental physics can govern in two disparate systems (elementary particles and conventional superconductors) for which the energy scales differ by 15 orders of magnitude.